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  • Polarization beam splitter based on honeycomb-lattice photonic crystal ring resonators
    J. Mod. Optic. (IF 1.657) Pub Date : 2014-03-19
    Xiaofu Xu, Haifeng Gu, Yanmin Zheng, Maojin Wei, Dongmei Zheng, Ronghui Xiao, Zexuan Qiang

    A new polarization beam splitter is proposed based on a photonic crystal ring resonator (PCRR) composed of honeycomb-lattice cylindrical silicon rods in air. By shrinking the width of the bus waveguide and adjusting the radii of two nearest-neighbor center rods of the PCRR, an unpolarized beam can be separated well into TE and TM polarization states, respectively, at the backward and forward output ports. Simulation results obtained by the two-dimensional finite-difference time-domain technique show that the insertion losses are 3.58 dB and 3.08 dB, and the polarization extinction ratios are 21.42 dB and 28.53 dB for TE and TM polarization, respectively, at a 1566.7 nm center wavelength. The excess loss is less than 0.34 dB and its dimensions are roughly 43.2 μm × 27.52 μm. These findings offer potential practical applications in high-density photonic integrated circuits.

    更新日期:2019-11-27
  • Beam wander of partially coherent Airy beams
    J. Mod. Optic. (IF 1.657) Pub Date : 2014-03-19
    Wei Wen, Xiuxiang Chu

    The beam wander of a partially coherent Airy beam in a turbulent atmosphere was investigated. By using the extended Huygens–Fresnel integral, as analytical expression is derived for the second-order moment of a partially coherent Airy beam. Based on the theory proposed by Andrews, a general expression is obtained for the beam wander of a partially coherent Airy beam. With the help of the expression, various factors which impact on the beam wander are illustrated numerically. The results show that the beam wander of a partially coherent Airy beam decreases with the increase of the characteristic scale and the decrease of the coherent length or the exponent truncation factor. The value of the beam wander is a maximum when the exponent truncation factor is 0.63, no matter what the coherent lengths are. Our results provide an effective way to control the beam wander of a partially coherent Airy beam in practice.

    更新日期:2019-11-27
  • Thermal properties and two-dimensional photonic band gaps
    J. Mod. Optic. (IF 1.657) Pub Date : 2014-03-19
    Hussein A. Elsayed, Sahar A. El-Naggar, Arafa H. Aly

    The effect of temperature on a two-dimensional square lattice photonic crystal composed of Si rods arranged in an air background was investigated theoretically using the plane-wave expansion method. Both the thermal expansion effect and thermo-optical effect are considered simultaneously. We have discussed the role of temperature in creating the complete photonic band gap as a function of temperature. Two different shapes of rods, i.e. square and circular, are considered in the presence of the two polarization states, i.e. TE and TM waves. The numerical results show that the photonic band gap can be significantly enlarged compared to the photonic band gap at room temperature. The effect of temperature on the complete photonic band width in the cylindrical rods case is more significant. Cylindrical and square Si rods may work as a temperature sensor or filter, among many other potential applications.

    更新日期:2019-11-27
  • Efficient method for lasing eigenvalue problems of periodic structures
    J. Mod. Optic. (IF 1.657) Pub Date : 2014-03-19
    Yuexia Huang, Ya Yan Lu

    Lasing eigenvalue problems (LEPs) are non-conventional eigenvalue problems involving the frequency and gain threshold at the onset of lasing directly. Efficient numerical methods are needed to solve LEPs for the analysis, design and optimization of microcavity lasers. Existing computational methods for two-dimensional LEPs include the multipole method and the boundary integral equation method. In particular, the multipole method has been applied to LEPs of periodic structures, but it requires sophisticated mathematical techniques for evaluating slowly converging infinite sums that appear due to the periodicity. In this paper, a new method is developed for periodic LEPs based on the so-called Dirichlet-to-Neumann maps. The method is efficient since it avoids the slowly converging sums and can easily handle periodic structures with many arrays.

    更新日期:2019-11-27
  • Temperature-dependent, polarization-induced bias errors in a resonator integrated optical gyroscope
    J. Mod. Optic. (IF 1.657) Pub Date : 2014-03-19
    Ming Lei, Lishuang Feng, Yinzhou Zhi

    The performance of a resonator integrated optical gyroscope (RIOG) is inevitably influenced by polarization noise. In this work, the effects of temperature-dependent polarization on the performances of an integrated optical resonator (IOR) and a RIOG are formulated mathematically and analyzed. Firstly, resonant curves with different polarization extinction ratios (PERs) and different temperature fluctuations are demonstrated. The main performances of the IOR, i.e. depth and full width at half maximum (FWHM), are not only influenced by the waveguide birefringence, but also by the intensity coupling coefficient of the couplers, both of which change with the variation of temperature. Secondly, the relationship between the variation of temperature and the variation of depth, as well as the FWHM, are obtained. Thirdly, in order to evaluate the zero bias error caused by the temperature-dependent polarization, resonant asymmetry ratio (RAR) is introduced, which is strongly dependent on the temperature fluctuation. A relationship between the bias error caused by the polarization and the temperature fluctuation is proposed. A large PER of the input beam and a high temperature stability are required to reduce the bias error and achieve a high bias stability of the silica RIOG.

    更新日期:2019-11-27
  • All-optical switching based on the electromagnetically induced transparency effect of an active photonic crystal microcavity
    J. Mod. Optic. (IF 1.657) Pub Date : 2014-03-19
    Y. He, T. Wang, W. Yan, X.M. Li, C.B. Dong, J. Tang, B. Liu

    We report a new all-optical switching in a two-dimensional photonic crystal microcavity made of semiconductor multiple quantum wells and realized based on the electromagnetically induced transparency effect with exciton and two-exciton energy levels. We use the quantum coherence effects to achieve small absorption of the probe field, and the absorption of the probe field can be adjusted by controlling the pump field and decay rate. We turn the control field into pulses of light field so that we can regulate the efficiency of the switch. Through selecting the appropriate control light field intensity, we can obtain a switching efficiency of 85% and a switching time is 10 ps. This result can be used for the development of new types of nanoelectronic devices for realizing the switching process.

    更新日期:2019-11-27
  • Spectral–temporal analysis of dispersive wave generation in photonic crystal fibers of different dispersion slope
    J. Mod. Optic. (IF 1.657) Pub Date : 2014-03-19
    Hua Yang, Fang Han, Hui Hu, Weibin Wang, Qilin Zeng

    Based on the generalized nonlinear Schrödinger equation, we present a numerical investigation of dispersive wave generation in photonic crystal fibers pumped with femtosecond pulses in the anomalous dispersion region. Both positive dispersion slope and negative dispersion slope for pump wavelength are studied. It is demonstrated that the wavelength of the dispersive wave can be blue-shifted or red-shifted relative to the center wavelength of the soliton, depending on the dispersion slope of the pump wavelength. The spectral–temporal dynamics of dispersive wave generation is shown using the cross-correlation frequency-resolved optical gating (X-FROG) technique, which is numerically computed with a windowed Fourier transform. Further, we find a phenomenon that the X-FROG spectrogram of the corresponding output signal exhibits a parabolic shape, which is consistent with the wavelength dependence of the group delay. In particular, the phenomenon of soliton trapping of the dispersive wave is observed with an increase of pump power.

    更新日期:2019-11-27
  • Yield enhancement in whispering gallery mode biosensors: microfluidics and optical forces
    J. Mod. Optic. (IF 1.657) Pub Date : 2014-03-19
    Kiran Khosla, Jon D. Swaim, Joachim Knittel, Warwick P. Bowen

    We analyze the transport of 25 nm polystyrene nanoparticles through a microfluidic geometry housing a microtoroidal whispering gallery mode (WGM) sensor, taking into account diffusion, convection and optical forces. In particular, we look at the effects of tightly confining the flow of nanoparticles near the microtoroid’s equatorial rim, and calculate the average nanoparticle detection time as well as the total yield for passage of a 1  rμL sample. Compared to purely diffusive transport, flow rates on the order of 2 nL min -1 give yield enhancements of up to 15 ×, with nanoparticles being detected every 12 s. Even shorter detection times (1.2 s) can be achieved, but at the expense of lower yield. The sensor’s transport properties are further improved due to gradient optical forces exerted on the nanoparticles.

    更新日期:2019-11-27
  • Tunable ring-coupled Mach–Zehnder interferometer based on lithium niobate
    J. Mod. Optic. (IF 1.657) Pub Date : 2014-03-19
    Mehmet E. Solmaz

    The fabrication and characterization are reported of a Fano resonance-based electro-optically tunable ring resonator-coupled Mach–Zehnder interferometer device based on a chalcogenide–lithium niobate hybrid waveguide system. The experiments reveal inherent asymmetric lineshapes that can be flipped to a near symmetrical resonance by applying a dc voltage of ~10 V across the electrode at the MZI non-resonator arm. Further increase in voltage yields the reverse of initial asymmetry. The optical filter-based transfer-matrix model easily explains the experimental data and indicates ways to further enhance the usability of such architecture.

    更新日期:2019-11-27
  • Ellipsometry of anisotropic (sub)nanometric dielectric films on absorbing materials
    J. Mod. Optic. (IF 1.657) Pub Date : 2014-03-19
    Peep Adamson

    A new ellipsometric method was developed for determining optical parameters of ultrathin uniaxially anisotropic dielectric films. It is based on the phase conversion measurements of polarized reflected light at different incident angles. The elaborated technique possesses very high sensitivity and is successfully applicable even for sub-nanometric layers because the phase changes for such layers on absorbing substrates are generally markedly greater than the measurement error. Another interesting facet of this method lies in the fact that the traditional model-based regression analysis is not used for data handling. The inversion problem is resolved on the basis of an original analytical approach, which has no need of initial guesses for the desired parameters. The presented method is tested using a numerical simulation.

    更新日期:2019-11-27
  • An analysis of waveguide resonator coupling in a microsphere and confocal cavity whispering gallery system
    J. Mod. Optic. (IF 1.657) Pub Date : 2014-03-19
    C.Y. Zhao, F. Ge

    There are two kinds of coupling method in an optical-fiber taper coupled to a silica-microsphere whispering gallery mode (WGM) system. One is indirect coupling; another is direct coupling. In the case of indirect coupling, pump light is injected from the side of the micro-cavity. Thus, a ring mode results from the total internal reflection excited by spherical ring standing wave. In the case of direct coupling, pump light is injected from the front of the micro-cavity. Thus, a concentric mode or confocal mode result from the transmission input excited by spherical axial-oscillating standing wave. The ring mode and concentric mode have both been adopted in microsphere cavities. However, the confocal mode has not been reported, either in theory or experiment. In this paper, we adopt a micro-spheroid resonator as the confocal cavity, which can be obtained by exerting a pressure on the microsphere cavity. Thus, the confocal mode is produced in a micro-spheroid resonator. Then we investigate waveguide resonator coupling in a microsphere and confocal cavity WGM system. Finally, we make a detailed analysis of the full width at half maximum (FWHM), ζ, and quality factor, Q, between the indirect coupling and the direct coupling. We find that for the concentric mode, Q=6.74×104, which is nearly the same as that of the ring mode, Q = 7.2 × 104. For large diameter of injection laser beam, the confocal mode can obtain higher quality factor (Q > 1.202 × 106) than that of the ring mode (Q = 7.2 × 104).

    更新日期:2019-11-27
  • Optical solitons in nonlinear directional couplers with spatio-temporal dispersion
    J. Mod. Optic. (IF 1.657) Pub Date : 2014-03-19
    Michelle Savescu, A.H. Bhrawy, A.A. Alshaery, E.M. Hilal, Kaisar R. Khan, M.F. Mahmood, Anjan Biswas

    This paper addresses solitons in nonlinear directional couplers in non-Kerr law media, with spatio-temporal dispersion. Both twin-core couplers as well as multiple-core couplers are studied. The nonlinearities studied are Kerr law, power law, parabolic law, dual-power law and log law. Bright, dark and singular soliton solutions of the governing equation are studied.

    更新日期:2019-11-27
  • Corrigendum
    J. Mod. Optic. (IF 1.657) Pub Date : 2014-03-19

    (2014). Corrigendum. Journal of Modern Optics: Vol. 61, No. 5, pp. 459-459.

    更新日期:2019-11-27
  • Analysis of light scattering from anisotropic particles using FDTD method
    J. Mod. Optic. (IF 1.657) Pub Date : 2019-10-08
    Fatih Kaburcuk, Çağlar Duman

    Light scattering from small anisotropic particles has important interests in the applications of meteorology, oceanography, communication, and nanotechnology. In this paper, the light scattering from uniaxial and biaxial small particles is investigated using the anisotropy formulation based on the finite-difference time-domain (FDTD) method, although this method has been used to analyse the isotropic particles. The obtained light scattering solutions from the isotropic small particle using the FDTD method are compared with the exact solutions obtained by Mie theory. The effects of the anisotropy and the rotation of optical axes on the light scattering are also investigated. Numerical results show that the distribution of scattered light is strongly affected by the anisotropy of the particles. Therefore, the anisotropy of the scattering particles is an important factor in several applications such as free-space optical communications.

    更新日期:2019-11-04
  • The existence and evolution of fast-decaying Bessel modes in cylindrical hollow waveguides and in free space
    J. Mod. Optic. (IF 1.657) Pub Date : 2019-10-09
    G. Nyitray, A. Nagyváradi, M. Koniorczyk

    The fundamental problem of propagation invariant Bessel beams is that they are not square-integrable in the transverse direction, and are therefore associated with an infinite power flux. Hence, truncated Bessel beams are typically considered instead. These are generated by finite apertures or apodized by a Gaussian transmittance. We obtain a different square-integrable solution of the Bessel field distribution. We show that the cylindrical symmetric hollow waveguide as a resonator modulates its own field during its propagation. These fast-decaying modes satisfy Maxwell's equations and can be expressed in analytic form.

    更新日期:2019-11-04
  • Doppler-shifted laser self-mixing interferometry for enhanced detection sensitivity
    J. Mod. Optic. (IF 1.657) Pub Date : 2019-10-04
    Ke Kou, Cuo Wang, Guanlei Zhang

    Laser self-mixing interferometry (SMI) is a well-known measurement technique having been applied to the fields of geometrical quantities detection, medical treatment and industry manufacturing. Its detection sensitivity can be improved by frequency shifting towards the laser's relaxation oscillation frequency (ROF), which has always been implemented by a pair of acousto-optic modulators (AOM). This manuscript presents a novel method based on Doppler effect for frequency shifting, which is based on a rotating disk and has the advantages of convenient adjustment and low cost. The theoretical analysis in the form of Doppler shift and time-delayed rate equations is followed, and simulative and experimental results are included to prove its validity. To our knowledge, this technique has not been used in practice till now, and the proposed structure, with these advantages, can find significant applications in designing high performance SMI sensors, and can extend SMI measurement to more kinds of non-cooperative surfaces.

    更新日期:2019-11-04
  • Least-squares solutions of the reduced biquaternion matrix equation AX=B and their applications in colour image restoration
    J. Mod. Optic. (IF 1.657) Pub Date : 2019-10-14
    Hidayet Hüda Kösal

    In this study, we derive the expressions of the minimal norm least-squares solution for the reduced biquaternion (RB) matrix equation AX=B by using the e1−e2 form of RB matrices, and the Moore–Penrose generalized inverse. Moreover, we investigate their applications in colour image restoration. Therefore, many useful image restoration methods can be extended to reduced biquaternion algebra without separating the colour image into three channels. To prove the authenticity of our results and to distinguish them from existing ones, some illustrative examples are also given.

    更新日期:2019-11-04
  • Propagation properties of collinear self-decelerating Airy–Elegant–Laguerre–Gaussian wave packets in free space
    J. Mod. Optic. (IF 1.657) Pub Date : 2019-10-11
    Xiaping Zhang

    Based on the analytical expression of the spatiotemporal collinear self-decelerating Airy Elegant–Laguerre–Gaussian (AiELG) wave packets by solving the (3+1)D free-space Schrödinger equation, we have investigated the collinear self-decelerating AiELG propagation properties in detail. Analysis results show that the different spatiotemporal profiles can be accessed by selecting a different mode number or relative amplitude. The spatiotemporal profiles will rotate if the mode parameter A≠0 or mode number |m1|=|m2|≠0 in the propagation. The wave packets will also rotate when the relative phase are varied. The direction of the energy flow of collinear wave packets is in helical clockwise distribution if mode number m1=m2>0 or mode parameter A>0, otherwise, the direction is in helical anticlockwise distribution if mode number m1=m2<0 or mode parameter A<0, which is the reason of rotation of the wave packets during propagation. The spatiotemporal hollow self-decelerating AiELG wave packets are accessed with m1=m2.

    更新日期:2019-11-04
  • Small-angle measurement in laser autocollimation based on a common-path compensation method
    J. Mod. Optic. (IF 1.657) Pub Date : 2019-10-13
    Yan Guo, Haobo Cheng, Yongfu Wen, Hengyu Wu, Yumin Wu

    In this study, a common-path compensation method is proposed for the laser beam drift resulting from the air parameters to enhance the stability of small-angle measurement in laser autocollimation. The measuring and reference beams generated with this method can propagate along approximately the same route such that the drifts in the two beams are nearly equal. Therefore, the angular drift of the measuring beam can be adequately compensated by that of the reference beam. The compensation principle was analyzed, and the experimental results revealed that, with three types of air parameter disturbances, the static measurement stability was better than 0.193 arcsec in 100 min after compensation, and the compensation rate was higher than 86.6%. Additionally, the dynamic measurement stability was 0.227 arcsec in 50 s after compensation, and the compensation rate was 53.6%. It is confirmed that the proposed method is effective for laser autocollimation.

    更新日期:2019-11-04
  • Application of improved particle swarm optimization algorithm in solving camera extrinsic parameters
    J. Mod. Optic. (IF 1.657) Pub Date : 2019-10-22
    Weimin Li, Kun Zhong

    A hybrid particle swarm optimization algorithm for determining extrinsic parameters of the camera, with the intrinsic parameters known, is presented in this paper. An adaptive inertia weighting strategy is designed, and improved crossover and mutation operation are performed. Taking the result of the particle swarm optimization algorithm as the initial value, the extrinsic parameters of the camera are optimized by Gauss–Newton method. The simulation results demonstrate that, when the standard deviation of image noise is 0.1 pixels, the mean relative error of rotation angle is less than 0.04844% and the mean relative error of translation vector is less than 0.05583%. The experimental results show that the mean reprojection error of the proposed algorithm is no more than 0.06045 pixels. The algorithm can achieve high precision and robustness in practical applications. Besides, the algorithm is computational efficient.

    更新日期:2019-11-04
  • 405 nm ultraviolet photodetector based on tungsten disulphide thin film grown by drop casting method
    J. Mod. Optic. (IF 1.657) Pub Date : 2019-10-23
    Harith Ahmad, Haroon Rashid

    In this work, a tungsten disulphide or WS2 based heterojunction photodetector device is fabricated on top of Si substrate by simple drop casting. Raman shifts are observed at 350.16 and 419.36 cm−1, confirming the successful growth of the WS2 and the non-stoichiometric WS2 layers which are verified by energy-dispersive X-ray (EDX) spectroscopy. The device is characterized for its optoelectronic properties in the ultraviolet (UV) range of 405 nm. Current–voltage (I–V) measurement is performed to obtain the I–V curves of the photodiode under laser illumination at 30.219, 56.335, 80.457, 106.998 and 129.28 mW.cm−2. The photocurrent is found to be highly dependent on the laser power. The fabricated device has a high responsivity of 145.52 mA/W and a high detectivity of 1.248 × 1011 Jones for an incident laser power density of 129.28 mW.cm−2. These observed results are promising and indicate the viability of the proposed design for optoelectronic applications.

    更新日期:2019-11-04
  • Modification of the support and active correction method for an experimental thin primary mirror
    J. Mod. Optic. (IF 1.657) Pub Date : 2019-10-28
    Xiaolin Dai, Hao Xian, Jinlong Tang, Xuejun Zhang, Yudong Zhang

    This paper firstly introduces the principle of floatation support as well as its force distribution algorithms, then proposes a new floatation support algorithm. The new algorithm directly utilizes the image of the mirror surface to calculate the adjusting forces of the actuators. We use a 1.2 m thin primary mirror to verify the performances of all the algorithms, the results show the new algorithm is as effective as the best traditional algorithm. Further study shows that compared with the force-based-algorithm, the new algorithm is easier to be influenced by the fixed point’s position deviation and the S–H’s detection error, however, it’s more helpful to simplify the hardware request of floatation support as it doesn’t need the force sensors.

    更新日期:2019-11-04
  • A fast stitching method based on verticality calibration using three marker points
    J. Mod. Optic. (IF 1.657) Pub Date : 2019-10-23
    Chunzhi Huang, Yanjun Fu, Kejun Zhong, Xiaoqi Cai, Bingliang Guan

    The speed of three-dimensional (3D) reconstruction based on structured light is affected by the stitching speed. In order to improve the stitching speed, a fast stitching method based on verticality calibration is proposed. Firstly, vertical calibration is used to place the camera perpendicular to the reference plane; then, the rotation axis is corrected. A normal vector of a plane based on three marker points is determined, and the decomposition vector perpendicular to the corrected rotation axis is obtained. Secondly, the angle between the decomposition vector before and after transformation is calculated. Finally, the rotation (R) matrix and translation (T) matrix are solved, and the stitching is completed. Experiments show that this method can improve the speed of surface stitching in 3D reconstruction based on structured light. The average error of stitching is 0.1103 mm and the standard deviation is 0.0327 mm when the stitching area is 250 mm × 90 mm.

    更新日期:2019-11-04
  • Effects of anisotropy on the depth of penetration of photons into turbid media.
    J. Mod. Optic. (IF 1.657) Pub Date : 2010-01-01
    Victor Chernomordik,Amir H Gandjbakhche,George H Weiss,Leonardo Dagdug

    Biomedical applications of near infrared radiation (NIR) techniques (i.e., based on light wavelengths roughly between 400 and 1100 nm) require that a preliminary estimate of the tissue volume being investigated be found. One possible estimate is the depth to which a photon penetrates a tissue before it eventually emerges at a separating plane at a given time. A simple model for this problem can be based on a lattice random walk and was initially analyzed when the associated optical coefficients are isotropic with respect to the geometry. Here we include the effects of anisotropy in the optical coefficients, finding that at long times the statistical properties of the depth of penetration can be accounted for by very simple scaling factors while at short times the anisotropy factors can be quite significant.

    更新日期:2019-11-01
  • Stimulated Raman scattering: old physics, new applications.
    J. Mod. Optic. (IF 1.657) Pub Date : 2010-04-01
    Vladislav V Yakovlev,Georgi I Petrov,Hao F Zhang,Gary D Noojin,Michael L Denton,Robert J Thomas,Marlan O Scully

    Stimulated Raman scattering as a promising way of expanding the tunability of ultrafast lasers and as an exciting new biomedical imaging modality capable of selective excitation and chemically-specific diagnostics of molecular species.

    更新日期:2019-11-01
  • Analytical Capabilities of Coherent Anti-Stokes Raman Scattering Microspectroscopy.
    J. Mod. Optic. (IF 1.657) Pub Date : 2009-09-04
    Rajan Arora,Georgi I Petrov,Vladislav V Yakovlev

    Nonlinear Raman scattering is an emerging spectroscopy technique for non-invasive microscopic imaging. It can produce a fluorescence background free vibrational spectrum from a microscopic volume of a sample providing chemically specific information about its molecular composition. We analyze the ability of nonlinear Raman microspectroscopy to detect low concentrated molecular species and evaluate its applicability to study complex solutions.

    更新日期:2019-11-01
  • Fifteen years of cold matter on the atom chip: promise, realizations, and prospects.
    J. Mod. Optic. (IF 1.657) Pub Date : 2016-08-09
    Mark Keil,Omer Amit,Shuyu Zhou,David Groswasser,Yonathan Japha,Ron Folman

    Here we review the field of atom chips in the context of Bose-Einstein Condensates (BEC) as well as cold matter in general. Twenty years after the first realization of the BEC and 15 years after the realization of the atom chip, the latter has been found to enable extraordinary feats: from producing BECs at a rate of several per second, through the realization of matter-wave interferometry, and all the way to novel probing of surfaces and new forces. In addition, technological applications are also being intensively pursued. This review will describe these developments and more, including new ideas which have not yet been realized.

    更新日期:2019-11-01
  • Paraxial light distribution in the focal region of a lens: a comparison of several analytical solutions and a numerical result.
    J. Mod. Optic. (IF 1.657) Pub Date : 2015-02-24
    Yang Wu,Damien P Kelly

    The distribution of the complex field in the focal region of a lens is a classical optical diffraction problem. Today, it remains of significant theoretical importance for understanding the properties of imaging systems. In the paraxial regime, it is possible to find analytical solutions in the neighborhood of the focus, when a plane wave is incident on a focusing lens whose finite extent is limited by a circular aperture. For example, in Born and Wolf's treatment of this problem, two different, but mathematically equivalent analytical solutions, are presented that describe the 3D field distribution using infinite sums of [Formula: see text] and [Formula: see text] type Lommel functions. An alternative solution expresses the distribution in terms of Zernike polynomials, and was presented by Nijboer in 1947. More recently, Cao derived an alternative analytical solution by expanding the Fresnel kernel using a Taylor series expansion. In practical calculations, however, only a finite number of terms from these infinite series expansions is actually used to calculate the distribution in the focal region. In this manuscript, we compare and contrast each of these different solutions to a numerically calculated result, paying particular attention to how quickly each solution converges for a range of different spatial locations behind the focusing lens. We also examine the time taken to calculate each of the analytical solutions. The numerical solution is calculated in a polar coordinate system and is semi-analytic. The integration over the angle is solved analytically, while the radial coordinate is sampled with a sampling interval of [Formula: see text] and then numerically integrated. This produces an infinite set of replicas in the diffraction plane, that are located in circular rings centered at the optical axis and each with radii given by [Formula: see text], where [Formula: see text] is the replica order. These circular replicas are shown to be fundamentally different from the replicas that arise in a Cartesian coordinate system.

    更新日期:2019-11-01
  • Advanced technologies for future ground-based, laser-interferometric gravitational wave detectors.
    J. Mod. Optic. (IF 1.657) Pub Date : 2015-02-24
    Giles Hammond,Stefan Hild,Matthew Pitkin

    We present a review of modern optical techniques being used and developed for the field of gravitational wave detection. We describe the current state-of-the-art of gravitational waves detector technologies with regard to optical layouts, suspensions and test masses. We discuss the dominant sources and noise in each of these subsystems and the developments that will help mitigate them for future generations of detectors. We very briefly summarise some of the novel astrophysics that will be possible with these upgraded detectors.

    更新日期:2019-11-01
  • Detectors for single-molecule fluorescence imaging and spectroscopy.
    J. Mod. Optic. (IF 1.657) Pub Date : 2007-01-01
    X Michalet,O H W Siegmund,J V Vallerga,P Jelinsky,J E Millaud,S Weiss

    Single-molecule observation, characterization and manipulation techniques have recently come to the forefront of several research domains spanning chemistry, biology and physics. Due to the exquisite sensitivity, specificity, and unmasking of ensemble averaging, single-molecule fluorescence imaging and spectroscopy have become, in a short period of time, important tools in cell biology, biochemistry and biophysics. These methods led to new ways of thinking about biological processes such as viral infection, receptor diffusion and oligomerization, cellular signaling, protein-protein or protein-nucleic acid interactions, and molecular machines. Such achievements require a combination of several factors to be met, among which detector sensitivity and bandwidth are crucial. We examine here the needed performance of photodetectors used in these types of experiments, the current state of the art for different categories of detectors, and actual and future developments of single-photon counting detectors for single-molecule imaging and spectroscopy.

    更新日期:2019-11-01
  • Potential signal to accommodation from the Stiles-Crawford effect and ocular monochromatic aberrations.
    J. Mod. Optic. (IF 1.657) Pub Date : 2010-09-14
    Lawrence R Stark,Philip B Kruger,Frances J Rucker,William H Swanson,Nathan Schmidt,Caitlin Hardy,Hadassa Rutman,Theodore Borgovan,Sean Burke,Mustanser Badar,Raj Shah

    The purpose of this study is to determine if cues within the blurred retinal image due to the Stiles-Crawford (SC) effect and the eye's monochromatic aberrations can drive accommodation with a small pupil (3 mm) that is typical of bright photopic conditions.The foveal, psychophysical SC function (17 min arc) and ocular monochromatic aberrations were measured in 21 visually normal adults. The retinal image of a 10.2 min arc disc was simulated for spherical defocus levels of -1 D, 0 D and +1 D in each of four conditions consisting of combinations of the presence or absence of the individual SC function and monochromatic aberrations with a 3 mm pupil. Accommodation was recorded in eleven participants as each viewed the simulations through a 0.75-mm pinhole.The SC effect alone did not provide a significant cue to accommodation. Monochromatic aberrations provided a statistically significant but rather small cue to monocular accommodation.

    更新日期:2019-11-01
  • Can precursors improve the transmission of energy at optical frequencies?
    J. Mod. Optic. (IF 1.657) Pub Date : 2009-07-30
    David Lukofsky,Jonathan Bessette,Heejeong Jeong,Elsa Garmire,Ulf Osterberg

    The recent interest in precursors has been fuelled by the possibility of using them for the efficient transmission of information through absorbing media at radio or optical frequencies. Here we demonstrate that the low attenuation experienced by the Brillouin precursor is attributed to the inherently low absorption of dispersive media near DC, a characteristic already exploited with communications systems using the extremely low frequency (ELF) band. Pulses, regardless of their temporal width and carrier frequency, always obey Beer's law as long as they propagate in the linear time invariant regime. We conclude with an FDTD simulation of the Maxwell-Bloch equations that shows how optical coherent bleaching effects, which take place in the linear time variant regime of the Lorentz oscillator model, can cause sustained deviations from Beer's law over relatively long distances of water.

    更新日期:2019-11-01
  • Rotation of Electromagnetic Fields and the Nature of Optical Angular Momentum.
    J. Mod. Optic. (IF 1.657) Pub Date : 2010-08-01
    Stephen M Barnett

    The association of spin and orbital angular momenta of light with its polarization and helical phase fronts is now well established. The problems in linking this with electromagnetic theory, as expressed in Maxwell's equations, are rather less well known. We present a simple analysis of the problems involved in defining spin and orbital angular momenta for electromagnetic fields and discuss some of the remaining challenges. Crucial to our investigation is the duplex symmetry between the electric and magnetic fields.

    更新日期:2019-11-01
  • Image chorioretinal vasculature in albino rats using photoacoustic ophthalmoscopy.
    J. Mod. Optic. (IF 1.657) Pub Date : 2011-01-01
    Qing Wei,Tan Liu,Shuliang Jiao,Hao F Zhang

    We imaged the microvascular network in both the retina and the choroid in an albino rat eye using photoacoustic ophthalmoscopy guided by optical coherence tomography. Relying on optical absorption and ultrasonic detection, photoacoustic ophthalmoscopy can image both retinal and choroidal vessel networks with high contrast.

    更新日期:2019-11-01
  • Dynamic intrinsic optical signal monitoring of electrically stimulated inner retinal neural response.
    J. Mod. Optic. (IF 1.657) Pub Date : 2012-06-20
    Yi-Chao Li,Jian-Min Luo,Rong-Wen Lu,Kai-Mao Liu,Alexander Miles Levy,Xin-Cheng Yao

    Dynamic monitoring of stimulus-evoked inner neural response is important for functional validation of stimulation protocols of retinal prosthetic devices. In this paper, we demonstrate label-free intrinsic optical signal (IOS) imaging of electrically stimulated inner neural response in freshly isolated mouse retinas. While single-pulse stimulation evoked rapid IOS within 20 ms, pulse-train stimulation indicated that the fast IOS response can follow frequency stimulation up to at least 8 Hz. Fast IOS imaging promises a noninvasive method for high resolution examination of electrically evoked retinal response, without artifact contamination of electrical stimulus.

    更新日期:2019-11-01
  • Functional imaging of glucose-evoked rat islet activities using transient intrinsic optical signals.
    J. Mod. Optic. (IF 1.657) Pub Date : 2012-05-01
    Xin-Cheng Yao,Wan-Xing Cui,Yi-Chao Li,Wei Zhang,Rong-Wen Lu,Anthony Thompson,Franklin Amthor,Xu-Jing Wang

    We demonstrate intrinsic optical signal (IOS) imaging of intact rat islet, which consists of many endocrine cells working together. A near-infrared digital microscope was employed for optical monitoring of islet activities evoked by glucose stimulation. Dynamic NIR images revealed transient IOS responses in the islet activated by low-dose (2.75mM) and high-dose (5.5mM) glucose stimuli. Comparative experiments and quantitative analysis indicated that both glucose metabolism and calcium/insulin dynamics might contribute to the observed IOS responses. Further investigation of the IOS imaging technology may provide a high resolution method for ex vivo functional examination of the islet, which is important for advanced study of diabetes associated islet dysfunctions and for improved quality control of donor islets for transplantation.

    更新日期:2019-11-01
  • Quasi-balanced two-wave mixing interferometer for remote ultrasound detection.
    J. Mod. Optic. (IF 1.657) Pub Date : 2013-12-19
    Armin Hochreiner,Bernhard Reitinger,Klaus-Dieter Bouchal,Saeid Zamiri,Peter Burgholzer,Thomas Berer

    We present an improved detection scheme for a two-wave mixing interferometer with a Bi12SiO20 crystal. The proposed detection scheme allows quasi-balanced detection of ultrasonic signals whereby electrical disturbances are suppressed. Quasi-balancing is achieved by changing the polarity of the high voltage at the photorefractive crystal, leading to an inversion of the optical interference signal, in combination with inversion of the detector signal using a signal inverter before the data acquisition device. The polarity of the high voltage is changed by utilizing an H-bridge consisting of five high-voltage relays. Microcontrollers are used to synchronize the reversion of the high voltage at the photorefractive crystal and the inversion of the measured signals. We demonstrate remote measurement of ultrasonic waves and shown that electrical disturbances are suppressed using the quasi-balanced mode.

    更新日期:2019-11-01
  • Cone directionality from laser ray tracing in normal and LASIK patients.
    J. Mod. Optic. (IF 1.657) Pub Date : 2009-01-01
    Susana Marcos,Stephen A Burns

    Laser ray tracing, a technique originally developed to measure ocular aberrations from the deviations of the local ray aberrations as a function of entry pupil, was used to assess cone directionality in 29 normal eyes (seven of which underwent LASIK surgery) and seven eyes after LASIK corneal refractive surgery for myopia. The total intensity of the retinal aerial images was computed as a function of the entry location of the illuminated beam. The measured intensity distribution was fit to a two-dimensional Gaussian function plus a constant background. The maximum of the distribution represents the pupillary location toward which the cone photoreceptors are oriented (peak of the optical Stiles-Crawford, SCE, function). We found the average SCE peak location was located 0.43 ± 0.96mm nasally and 0.60 ± 0.87mm inferiorly to the center of the pupil. In general, there was not a relation between the pupillary area of best quality and SCE peak location, either pre-operatively or post-operatively. The cone directionality shape factor was also unchanged by surgery. However, in two eyes, pre- and post-operative SCE peak location changed significantly. LASIK refractive surgery decreased the MTF in all eyes, even when the actual SCE directionality of the subject is considered. In the two eyes that showed significantly different SCE peak location, the apodized post-operative MTF with the post-operative SCE peak exceeded the simulated post-operative MTF assuming no shift in the SCE peak. However, the statistical power of these two cases is low, and the general findings are consistent with the hypothesis that differences in optical quality are not a major driving mechanism for cone orientation.

    更新日期:2019-11-01
  • Light-matter interaction in free space.
    J. Mod. Optic. (IF 1.657) Pub Date : 2013-04-23
    Gerd Leuchs,Markus Sondermann

    We review recent experimental advances in the field of efficient coupling of single atoms and light in free space. Furthermore, a comparison of efficient free space coupling and strong coupling in cavity quantum electrodynamics (QED) is given. Free space coupling does not allow for observing oscillatory exchange between the light field and the atom which is the characteristic feature of strong coupling in cavity QED. Like cavity QED, free space QED does, however, offer full switching of the light field, a 180° phase shift conditional on the presence of a single atom as well as 100% absorption probability of a single photon by a single atom. Furthermore, free space cavity QED comprises the interaction with a continuum of modes.

    更新日期:2019-11-01
  • On a modified electrodynamics.
    J. Mod. Optic. (IF 1.657) Pub Date : 2012-10-30
    H R Reiss

    A modification of electrodynamics is proposed, motivated by previously unremarked paradoxes that can occur in the standard formulation. It is shown by specific examples that gauge transformations exist that radically alter the nature of a problem, even while maintaining the values of many measurable quantities. In one example, a system with energy conservation is transformed to a system where energy is not conserved. The second example possesses a ponderomotive potential in one gauge, but this important measurable quantity does not appear in the gauge-transformed system. A resolution of the paradoxes comes from noting that the change in total action arising from the interaction term in the Lagrangian density cannot always be neglected, contrary to the usual assumption. The problem arises from the information lost by employing an adiabatic cutoff of the field. This is not necessary. Its replacement by a requirement that the total action should not change with a gauge transformation amounts to a supplementary condition for gauge invariance that can be employed to preserve the physical character of the problem. It is shown that the adiabatic cutoff procedure can also be eliminated in the construction of quantum transition amplitudes, thus retaining consistency between the way in which asymptotic conditions are applied in electrodynamics and in quantum mechanics. The 'gauge-invariant electrodynamics' of Schwinger is shown to depend on an ansatz equivalent to the condition found here for maintenance of the ponderomotive potential in a gauge transformation. Among the altered viewpoints required by the modified electrodynamics, in addition to the rejection of the adiabatic cutoff, is the recognition that the electric and magnetic fields do not completely determine a physical problem, and that the electromagnetic potentials supply additional information that is required for completeness of electrodynamics.

    更新日期:2019-11-01
  • Age-dependent variation of the Gradient Index profile in human crystalline lenses.
    J. Mod. Optic. (IF 1.657) Pub Date : 2011-01-01
    A de Castro,D Siedlecki,David Borja,Stephen Uhlhorn,Jean-Marie Parel,Fabrice Manns,S Marcos

    PURPOSE: To reconstruct the gradient index (GRIN) profile of human crystalline lenses ex-vivo using Optical Coherence Tomography (OCT) imaging with an optimization technique and to study the dependence of the GRIN profile with age. METHODS: Cross-sectional images of nine isolated human crystalline lenses with ages ranging from 6 to 72 (post mortem time 1 to 4 days) were obtained using a custom-made OCT system. Lenses were extracted from whole cadaver globes and placed in a measurement chamber filled with preservation medium (DMEM). Lenses were imaged with the anterior surface up and then flipped over and imaged again, to obtain posterior lens surface profiles both undistorted and distorted by the refraction through the anterior crystalline lens and GRIN. The GRIN distribution of the lens was described with three variables by means of power function, with variables being the nucleus and surface index, and a power coefficient that describes the decay of the refractive index from the nucleus to the surface. An optimization method was used to search for the parameters that produced the best match of the distorted posterior surface. RESULTS: The distorted surface was simulated with accuracy around the resolution of the OCT system (under 15 µm). The reconstructed refractive index values ranged from 1.356 to 1.388 for the surface, and from 1.396 to 1.434 for the nucleus. The power coefficient ranged between 3 and 18. The power coefficient increased significantly with age, at a rate of 0.24 per year. CONCLUSION: Optical Coherence Tomography allowed optical, non-invasive measurement of the 2-D gradient index profile of the isolated human crystalline lens ex vivo. The age-dependent variation of the changes is consistent with previous data using magnetic resonance imaging, and the progressive formation of a refractive index plateau.

    更新日期:2019-11-01
  • Detecting mineral content in turbid medium using nonlinear Raman imaging: feasibility study.
    J. Mod. Optic. (IF 1.657) Pub Date : 2012-02-18
    Rajan Arora,Georgi I Petrov,Gary D Noojin,Patrick A Thomas,Michael L Denton,Benjamin A Rockwell,Robert J Thomas,Vladislav V Yakovlev

    Osteoporosis is a bone disease characterized by reduced mineral content with resulting changes in bone architecture, which in turn increases the risk of bone fracture. Raman spectroscopy has an intrinsic sensitivity to the chemical content of the bone, but its application to study bones in vivo is limited due to strong optical scattering in tissue. It has been proposed that Raman excitation with photoacoustic detection can successfully address the problem of chemically specific imaging in deep tissue. In this report, the principal possibility of photoacoustic imaging for detecting mineral content is evaluated.

    更新日期:2019-11-01
  • Smartphone-based imaging of the corneal endothelium at sub-cellular resolution.
    J. Mod. Optic. (IF 1.657) Pub Date : 2017-12-08
    Devrim Toslak,Damber Thapa,Muhammet Kazim Erol,Yanjun Chen,Xincheng Yao

    This aim of this study was to test the feasibility of smartphone-based specular microscopy of the corneal endothelium at a sub-cellular resolution. Quantitative examination of endothelial cells is essential for evaluating corneal disease such as determining a diagnosis, monitoring progression and assessing treatment. Smartphone-based technology promises a new opportunity to develop affordable devices to foster quantitative examination of endothelial cells in rural and underserved areas. In our study, we incorporated an iPhone 6 and a slit lamp to demonstrate the feasibility of smartphone-based microscopy of the corneal endothelium at a sub-cellular resolution. The sub-cellular resolution images allowed quantitative calculation of the endothelial cell density. Comparative measurements revealed a normal endothelial cell density of 2978 cells/mm2 in the healthy cornea, and a significantly reduced cell density of 1466 cells/mm2 in the diseased cornea with Fuchs' dystrophy. Our ultimate goal is to develop a smartphone-based telemedicine device for low-cost examination of the corneal endothelium, which can benefit patients in rural areas and underdeveloped countries to reduce health care disparities.

    更新日期:2019-11-01
  • Enhancement of intrinsic optical signal recording with split spectrum optical coherence tomography.
    J. Mod. Optic. (IF 1.657) Pub Date : 2017-11-14
    Damber Thapa,Benquan Wang,Yiming Lu,Taeyoon Son,Xincheng Yao

    Functional optical coherence tomography (OCT) of stimulus-evoked intrinsic optical signal (IOS) promises to be a new methodology for high-resolution mapping of retinal neural dysfunctions. However, its practical applications for non-invasive examination of retinal function have been hindered by the low signal-to-noise ratio (SNR) and small magnitude of IOSs. Split spectrum amplitude-decorrelation has been demonstrated to improve the image quality of OCT angiography. In this study, we exploited split spectrum strategy to improve the sensitivity of IOS recording. The full OCT spectrum was split into multiple spectral bands and IOSs from each sub-band were calculated separately and then combined to generate a single IOS image sequence. The algorithm was tested on in vivo images of frog retinas. It significantly improved both IOS magnitude and SNR, which are essential for practical applications of functional IOS imaging.

    更新日期:2019-11-01
  • High visibility in two-color above-threshold photoemission from tungsten nanotips in a coherent control scheme.
    J. Mod. Optic. (IF 1.657) Pub Date : 2017-08-18
    Timo Paschen,Michael Förster,Michael Krüger,Christoph Lemell,Georg Wachter,Florian Libisch,Thomas Madlener,Joachim Burgdörfer,Peter Hommelhoff

    In this article, we present coherent control of above-threshold photoemission from a tungsten nanotip achieving nearly perfect modulation. Depending on the pulse delay between fundamental ([Formula: see text]) and second harmonic ([Formula: see text]) pulses of a femtosecond fiber laser at the nanotip, electron emission is significantly enhanced or depressed during temporal overlap. Electron emission is studied as a function of pulse delay, optical near-field intensities, DC bias field and final photoelectron energy. Under optimized conditions modulation amplitudes of the electron emission of 97.5% are achieved. Experimental observations are discussed in the framework of quantum-pathway interference supported by local density of states simulations.

    更新日期:2019-11-01
  • Iterative deconvolution technique for measurements of diffraction-limited images on optical microscopes.
    J. Mod. Optic. (IF 1.657) Pub Date : 2015-03-17
    Wenlong Lu,Ming Chang,Po-Cheng Chen,Wun-Mao Luo

    Diffraction limit is usually a thorny problem in an optical inspection system. In this investigation, a model-based deconvolution technique was developed to recover diffraction-limited images, where images with sizes smaller than the diffraction limit could be recognized. Experiments were carried out with a traditional microscope at 200× magnification coupled with a halogen light source for a series of line width samples. The point spread function of the imaging optics was first obtained from an estimated model and then combined with a nonlinear deconvolution algorithm to calculate the full width at half maximum and reconstruct the line widths. Experimental results indicate that a measurement error below one pixel size of the measurement system is achievable. Accordingly, the target of nanoscale line width inspection based on a low cost and real-time image processing technique can be fulfilled, which greatly increases the ability of nanoscaling on optical microscopes.

    更新日期:2019-11-01
  • Non-moving Hadamard matrix diffusers for speckle reduction in laser pico-projectors.
    J. Mod. Optic. (IF 1.657) Pub Date : 2015-02-24
    Weston Thomas,Christopher Middlebrook

    Personal electronic devices such as cell phones and tablets continue to decrease in size while the number of features and add-ons keep increasing. One particular feature of great interest is an integrated projector system. Laser pico-projectors have been considered, but the technology has not been developed enough to warrant integration. With new advancements in diode technology and MEMS devices, laser-based projection is currently being advanced for pico-projectors. A primary problem encountered when using a pico-projector is coherent interference known as speckle. Laser speckle can lead to eye irritation and headaches after prolonged viewing. Diffractive optical elements known as diffusers have been examined as a means to lower speckle contrast. This paper presents a binary diffuser known as a Hadamard matrix diffuser. Using two static in-line Hadamard diffusers eliminates the need for rotation or vibration of the diffuser for temporal averaging. Two Hadamard diffusers were fabricated and contrast values measured showing good agreement with theory and simulated values.

    更新日期:2019-11-01
  • Nonlocal nonlinear refractive index of gold nanoparticles synthesized by ascorbic acid reduction: comparison of fitting models.
    J. Mod. Optic. (IF 1.657) Pub Date : 2015-02-24
    A Balbuena Ortega,M L Arroyo Carrasco,M M Méndez Otero,V L Gayou,R Delgado Macuil,H Martínez Gutiérrez,M D Iturbe Castillo

    In this paper, the nonlinear refractive index of colloidal gold nanoparticles under continuous wave illumination is investigated with the z-scan technique. Gold nanoparticles were synthesized using ascorbic acid as reductant, phosphates as stabilizer and cetyltrimethylammonium chloride (CTAC) as surfactant agent. The nanoparticle size was controlled with the CTAC concentration. Experiments changing incident power and sample concentration were done. The experimental z-scan results were fitted with three models: thermal lens, aberrant thermal lens and the nonlocal model. It is shown that the nonlocal model reproduces with exceptionally good agreement; the obtained experimental behaviour.

    更新日期:2019-11-01
  • New asymmetric propagation invariant beams obtained by amplitude and phase modulation in frequency space.
    J. Mod. Optic. (IF 1.657) Pub Date : 2015-02-24
    J Mendoza-Hernández,M L Arroyo Carrasco,M M Méndez Otero,S Chávez-Cerda,M D Iturbe Castillo

    In this paper, we demonstrate, numerically and experimentally that using the mask-lens setup used by Durnin to generate Bessel beams Durnin [Phys. Rev. Lett. 58, 1499 (1987)], it is possible to generate different kinds of propagation invariant beams. A modification in the amplitude or phase of the field that illuminates the annular slit is proposed that corresponds to modulation in frequency space. In particular, we characterize the new invariant beams that were obtained by modulating the amplitude of the annular mask and when the incident field was modulated with a one-dimensional quadratic or cubic phase. Experimental results using an amplitude mask are shown in order to corroborate the numerical predictions.

    更新日期:2019-11-01
  • Editorial.
    J. Mod. Optic. (IF 1.657) Pub Date : 2015-02-24

    更新日期:2019-11-01
  • Characterization of plasmonic hole arrays as transparent electrical contacts for organic photovoltaics using high-brightness Fourier transform methods.
    J. Mod. Optic. (IF 1.657) Pub Date : 2015-02-24
    Fernando E Camino,Chang-Yong Nam,Yutong T Pang,Jessica Hoy,Matthew D Eisaman,Charles T Black,Matthew Y Sfeir

    We present a methodology for probing light-matter interactions in prototype photovoltaic devices consisting of an organic semiconductor active layer with a semitransparent metal electrical contact exhibiting surface plasmon-based enhanced optical transmission. We achieve high-spectral irradiance in a spot size of less than 100 μm using a high-brightness laser-driven light source and appropriate coupling optics. Spatially resolved Fourier transform photocurrent spectroscopy in the visible and near-infrared spectral regions allows us to measure external quantum efficiency with high sensitivity in small-area devices (<1 mm2). This allows for rapid fabrication of variable-pitch sub-wavelength hole arrays in metal films for use as transparent electrical contacts, and evaluation of the evanescent and propagating mode coupling to resonances in the active layer.

    更新日期:2019-11-01
  • Quantum memories: emerging applications and recent advances.
    J. Mod. Optic. (IF 1.657) Pub Date : 2016-10-04
    Khabat Heshami,Duncan G England,Peter C Humphreys,Philip J Bustard,Victor M Acosta,Joshua Nunn,Benjamin J Sussman

    Quantum light-matter interfaces are at the heart of photonic quantum technologies. Quantum memories for photons, where non-classical states of photons are mapped onto stationary matter states and preserved for subsequent retrieval, are technical realizations enabled by exquisite control over interactions between light and matter. The ability of quantum memories to synchronize probabilistic events makes them a key component in quantum repeaters and quantum computation based on linear optics. This critical feature has motivated many groups to dedicate theoretical and experimental research to develop quantum memory devices. In recent years, exciting new applications, and more advanced developments of quantum memories, have proliferated. In this review, we outline some of the emerging applications of quantum memories in optical signal processing, quantum computation and non-linear optics. We review recent experimental and theoretical developments, and their impacts on more advanced photonic quantum technologies based on quantum memories.

    更新日期:2019-11-01
  • Quantum memory receiver for superadditive communication using binary coherent states.
    J. Mod. Optic. (IF 1.657) Pub Date : 2016-10-04
    Aleksandra Klimek,Michał Jachura,Wojciech Wasilewski,Konrad Banaszek

    We propose a simple architecture based on multimode quantum memories for collective readout of classical information keyed using a pair coherent states, exemplified by the well-known binary phase shift keying format. Such a configuration enables demonstration of the superadditivity effect in classical communication over quantum channels, where the transmission rate becomes enhanced through joint detection applied to multiple channel uses. The proposed scheme relies on the recently introduced idea to prepare Hadamard sequences of input symbols that are mapped by a linear optical transformation onto the pulse position modulation format [Guha, S. Phys. Rev. Lett.2011, 106, 240502]. We analyze two versions of readout based on direct detection and an optional Dolinar receiver which implements the minimum-error measurement for individual detection of a binary coherent state alphabet.

    更新日期:2019-11-01
  • Magnetically tuned, robust and efficient filtering system for spatially multimode quantum memory in warm atomic vapors.
    J. Mod. Optic. (IF 1.657) Pub Date : 2016-10-04
    M Dąbrowski,R Chrapkiewicz,W Wasilewski

    Warm atomic vapor quantum memories are simple and robust, yet suffer from a number of parasitic processes which produce excess noise. For operating in a single-photon regime precise filtering of the output light is essential. Here, we report a combination of magnetically tuned absorption and Faraday filters, both light-direction insensitive, which stop the driving lasers and attenuate spurious fluorescence and four-wave mixing while transmitting narrowband Stokes and anti-Stokes photons generated in write-in and readout processes. We characterize both filters with respect to adjustable working parameters. We demonstrate a significant increase in the signal-to-noise ratio upon applying the filters seen qualitatively in measurements of correlation between the Raman scattered photons.

    更新日期:2019-11-01
  • Photopolymerizable nanocomposite photonic materials and their holographic applications in light and neutron optics.
    J. Mod. Optic. (IF 1.657) Pub Date : 2016-09-07
    Yasuo Tomita,Eiji Hata,Keisuke Momose,Shingo Takayama,Xiangming Liu,Katsumi Chikama,Jürgen Klepp,Christian Pruner,Martin Fally

    We present an overview of recent investigations of photopolymerizable nanocomposite photonic materials in which, thanks to their high degree of material selectivity, recorded volume gratings possess high refractive index modulation amplitude and high mechanical/thermal stability at the same time, providing versatile applications in light and neutron optics. We discuss the mechanism of grating formation in holographically exposed nanocomposite materials, based on a model of the photopolymerization-driven mutual diffusion of monomer and nanoparticles. Experimental inspection of the recorded grating's morphology by various physicochemical and optical methods is described. We then outline the holographic recording properties of volume gratings recorded in photopolymerizable nanocomposite materials consisting of inorganic/organic nanoparticles and monomers having various photopolymerization mechanisms. Finally, we show two examples of our holographic applications, holographic digital data storage and slow-neutron beam control.

    更新日期:2019-11-01
  • Optimization of focusing through scattering media using the continuous sequential algorithm.
    J. Mod. Optic. (IF 1.657) Pub Date : 2016-03-29
    J V Thompson,B H Hokr,V V Yakovlev

    The ability to control the propagation of light through scattering media is essential for atmospheric optics, astronomy, biomedical imaging and remote sensing. The optimization of focusing light through a scattering medium is of particular interest for the case of highly scattering materials. Optical wavefront beam-shaping plays a critical role in optimizing such a propagation; however, an enormous field of adjustable parameters makes the overall task complicated. Here, we propose and experimentally evaluate several variations on the standard continuous sequential algorithm that hold a promise of revealing new, faster and more efficient optimization algorithms for selecting an optical wavefront to focus light through a scattering medium. We demonstrate that the order in which pixels are chosen in the continuous sequential algorithm can lead to a 2-fold decrease in the number of iterations required to reach a given enhancement.

    更新日期:2019-11-01
  • Quantifying light exposure patterns in young adult students.
    J. Mod. Optic. (IF 1.657) Pub Date : 2014-10-25
    Amanda A Alvarez,Christine F Wildsoet

    Exposure to bright light appears to be protective against myopia in both animals (chicks, monkeys) and children, but quantitative data on human light exposure are limited. In this study, we report on a technique for quantifying light exposure using wearable sensors. Twenty-seven young adult subjects wore a light sensor continuously for two weeks during one of three seasons, and also completed questionnaires about their visual activities. Light data were analyzed with respect to refractive error and season, and the objective sensor data were compared with subjects' estimates of time spent indoors and outdoors. Subjects' estimates of time spent indoors and outdoors were in poor agreement with durations reported by the sensor data. The results of questionnaire-based studies of light exposure should thus be interpreted with caution. The role of light in refractive error development should be investigated using multiple methods such as sensors to complement questionnaires.

    更新日期:2019-11-01
  • Application of a wide-field phantom eye for optical coherence tomography and reflectance imaging.
    J. Mod. Optic. (IF 1.657) Pub Date : 2016-01-08
    Anthony Corcoran,Gonzalo Muyo,Jano van Hemert,Alistair Gorman,Andrew R Harvey

    Optical coherence tomography (OCT) and reflectance imaging are used in clinical practice to measure the thickness and transverse dimensions of retinal features. The recent trend towards increasing the field of view (FOV) of these devices has led to an increasing significance of the optical aberrations of both the human eye and the device. We report the design, manufacture and application of the first phantom eye that reproduces the off-axis optical characteristics of the human eye, and allows the performance assessment of wide-field ophthalmic devices. We base our design and manufacture on the wide-field schematic eye, [Navarro, R. J. Opt. Soc. Am. A, 1985,2.] as an accurate proxy to the human eye and enable assessment of ophthalmic imaging performance for a [Formula: see text] external FOV. We used multi-material 3D-printed retinal targets to assess imaging performance of the following ophthalmic instruments: the Optos 200Tx, Heidelberg Spectralis, Zeiss FF4 fundus camera and Optos OCT SLO and use the phantom to provide an insight into some of the challenges of wide-field OCT.

    更新日期:2019-11-01
  • Spectral degree of polarization uniformity for polarization-sensitive OCT.
    J. Mod. Optic. (IF 1.657) Pub Date : 2015-12-23
    Bernhard Baumann,Stefan Zotter,Michael Pircher,Erich Götzinger,Sabine Rauscher,Martin Glösmann,Jan Lammer,Ursula Schmidt-Erfurth,Marion Gröger,Christoph K Hitzenberger

    Depolarization of light can be measured by polarization-sensitive optical coherence tomography (PS-OCT) and has been used to improve tissue discrimination as well as segmentation of pigmented structures. Most approaches to depolarization assessment for PS-OCT - such as the degree of polarization uniformity (DOPU) - rely on measuring the uniformity of polarization states using spatial evaluation kernels. In this article, we present a different approach which exploits the spectral dimension. We introduce the spectral DOPU for the pixelwise analysis of polarization state variations between sub-bands of the broadband light source spectrum. Alongside a comparison with conventional spatial and temporal DOPU algorithms, we demonstrate imaging in the healthy human retina, and apply the technique for contrasting hard exudates in diabetic retinopathy and investigating the pigment epithelium of the rat iris.

    更新日期:2019-11-01
  • Three-beam Doppler optical coherence tomography using a facet prism telescope and MEMS mirror for improved transversal resolution.
    J. Mod. Optic. (IF 1.657) Pub Date : 2015-12-23
    R Haindl,W Trasischker,B Baumann,M Pircher,C K Hitzenberger

    An improved three-beam Doppler optical coherence tomography system was developed. It utilizes a custom-made three-facet prism telescope to improve the transversal resolution at the sample. Furthermore, a two-axis gimbal-less MEMS mirror is used to minimize off-pivot beam movement at the pupil of the eye, enabling circular scanning for in vivo retinal measurements. We demonstrate the system's abilities for in vitro circular scanning to measure absolute flow and to reconstruct the full velocity vector on a bifurcation flow phantom. Moreover, in vivo retinal measurements using circular scanning around vessel bifurcations of healthy human volunteers were performed. Measurements of the absolute mean flow and its orientation are in good agreement with the expected values for in vitro measurements. For in vivo measurements, the in- and outflow of blood for retinal vessel bifurcations show an excellent agreement, demonstrating the reliability of the technique.

    更新日期:2019-11-01
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