An optimized Back-Propagation network (BP network) based on Genetic Algorithm (GA) was introduced to construct bidirectional reflectance distribution function (BRDF) model. To verify the performance of GA-BP network, two different kinds of space target materials were used for experiment. Based on the experimental data, we used GA to simulate the undetermined parameters of a five-parameter BRDF model

The peculiarities analysis in design of compressors for negatively chirped optical pulses parametrically amplified in double-chirped regime up to 1 J in multi-cascade system is done. A comparative analysis of the spatio-temporal distribution of the pulses at the output of various compressor schemes with an internal telescope has been performed. The analysis has been carried out using two methods: calculating

Some industrial uses of living cells involve genetic engineering or modification of cell’s external properties. However, these techniques commonly have high financial costs, do not take advantage of the natural properties of the cells, and have few applications in the photonics area. As the first technological application of living liquid crystals, we propose an all-passive optical diode using Bacillus

We demonstrate here, for the first time to the best of our knowledge, the method of classification and identification of metals, metal alloys using the color CCD images of femtosecond (fs) laser-induced plasma emissions. The non-gated color CCD images of the plasma emissions were used to train the machine learning algorithm for identification. We have also compared the obtained results with the fs-laser-induced

We develop a theoretical model of multimode rate equation that accurately describes mode evolution mechanism of prelase Q-switched Pr3+:YLF single longitudinal mode (SLM). We find that it is important to consider the effect of gain difference when calculating the mode competition time accurately. We identify that there is an optimal parameter for the two step signal of acoustic-optic modulator which

Nanofibre-based optical cavities are particularly useful for quantum optics applications, such as the development of integrated single-photon sources, and for studying fundamental light–matter interactions in cavity quantum electrodynamics (cQED). Although several techniques have been used to produce such cavities, focussed ion beam (FIB) milling is becoming popular; it can be used for the fabrication

Within the framework of the second order of perturbation theory and the dipole approximation, we derived simple formulas describing the temporal dynamics of ultrashort laser pulse scattering in terms of the scattering tensor and the Fourier transform of the strength of the electric field in a pulse. This expression was used for description of resonant scattering of an ultrashort pulse by an atom. We

In this paper, absolute-phase total internal reflection heterodyne interferometry is proposed for measuring a full-field refractive index. In this method, an optical configuration of prism-based total internal reflection is used. If an electro-optical modulator is driven by a sawtooth wave with an amplitude lower than the half-wave voltage, heterodyne interferometric signals can be generated in segment

A large and tunable lateral shift in a prism coupling system with a superconducting YBa2Cu3O7 film is theoretically analyzed. The dip of the reflectivity and magnitude of the lateral shift can be controlled by the temperature of the superconducting film. The sign of the lateral shift can be determined by the thickness of the superconducting film. The position of the minimum reflection and maximum Goos–Hänchen

A long-term stable single-longitudinal-mode (SLM) all polarization-maintaining (PM) compound-ring cavity fiber laser is reported. The results show that the PM fiber's strong ability to resist the environment disturbance allows finely designing the length of each secondary cavity in real time according to the main cavity under the laboratory environment, and then the effective longitudinal mode spacing

For the first time, the UV inductive nitrogen laser was created with generation energy of 11 mJ and pulse duration 10 ± 1 ns (FWHM). Lasing was obtained on two lines with wavelengths of 337.1 and 357.7 nm. The generation energy distribution over the cross section had a shape of a ring with diameter and width of about 40 and 2 mm, respectively.

In this article, we set up a theoretical model to investigate the physical mechanism of circularly polarized (CP) high-harmonic generation (HHG) by two-color relativistic driving lasers (with one at fundamental and the other at second harmonic). The compression effect of the electron density profile and the boundary oscillating are responsible for the harmonic emission. Based on this model, the scaling

We report on the realization of a displacement sensor based on an optical nanofiber. A single gold nano-sphere is deposited on top of a nanofiber and the system is placed within a standing wave which serves as a position ruler. Scattered light collected within the guided mode of the fiber gives a direct measurement of the nanofiber displacement. We calibrated our device and found a sensitivity up to

Excess micromotion of trapped ions leads to several adverse effects, such as modulating the absorption spectrum, shifting the transition frequency, and causing extra motional heating of ions. Moreover, it is hard to deal with, if there is no rf null point in a Paul trap. In this paper, two methods are proposed to control these adverse effects introduced by excess micromotion. The first method can eliminate

The fringe pattern obtained by optical interference is susceptible to speckle noise, which causes the fringes to be blurred to some extent. It is a critical step to achieve fringe smoothness while removing speckle noise. In this paper, we propose a new variable image decomposition model TGV–Hilbert–Shearlet, in which low-density fringes, high-density fringes, and noise are described by the total generalized

A new fast sensor for simultaneous high temperature diagnostics (above 800 K) of nitrogen oxide (NO) concentration and gas temperature (T) was developed based on the spectral fitting of low-resolution NO UV absorption near 226 nm. The sensor was intended for process control in future low-carbon footprint heavy process industries using renewable powered electro fuels (e.g. H2, NH3) or plasma torches

Quantum vision is currently emerging as an interdisciplinary field synthesizing the physiology of human vision with modern quantum optics. We recently proposed a biometric scheme based on the human visual system’s ability to perform photon counting. We here present a light stimulus source that can provide for the requirements of this biometric scheme, namely a laser light beam having a cross section

In this work, a novel single-shot pump-probe technique based on mirror array is proposed, which can be used to investigate the dynamics of nonlinear absorption with a single-shot femtosecond laser. Using this unique mirror array, the dispersion of femtosecond pulse laser caused by time delay can be avoided and the delay time can be increased effectively. Additionally, the energy requirements of the

The present paper proposes a novel denoising method to suppress multi-source noise and enhance the signal-to-noise ratio (SNR) of the phase-sensitive optical-time-domain reflectometer (Ф-OTDR). The method is based on complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN) and the interval thresholding. Firstly, the CEEMDAN is applied to the vibration signals to obtain a series

To achieve a high-sensitivity surface plasmon resonance sensor, a sensor based on Ag-MgF2 grating was designed and fabricated. A suitable-thickness MgF2 was suggested to prevent the oxidation of silver while avoiding reducing its plasmonic properties. The combination of an interference lithography approach, the material used for the fabrication of grating, and angular interrogation method led to a

Single crystals of pure and crystal violet (CV) dye-doped anthracene single crystals have been synthesized by solvent evaporation technique utilizing chloroform as the solvent. There is a significant enhancement in optical, mechanical, photoacoustical and third-order non-linear properties have been attained due to the incorporation of dye in the host material. The unit cell parameters and crystallinity

Designing efficient and compact couplers is crucial in hybrid integration of plasmonic components with conventional silicon-on-insulator components. Taper-funnel structures are conventionally used to couple light from a silicon strip waveguide to a metal–dielectric–metal plasmonic waveguide. In this paper, we investigate the effect of different parameters of the metallic funnel and the vertically and

A method for precise adjustment of the power splitting ratio for integrated optical splitters fabricated on lithium niobate substrates is proposed. The method is based on a local refractive index change caused by the photorefractive effect under external illumination of certain areas of waveguide power splitters. A fiber optic probe was used for precise positioning of an external illumination spot

The beam quality of diode-pumped alkali lasers (DPALs) is of major concern in the studies of these lasers. We report on experimental studies and modeling of the beam propagation factor M2 in flowing-gas Cs DPALs with stable optical resonators and of its dependence on the resonator geometry. The measured values of M2 are in agreement with those calculated using the optical model of multi-transverse

In spray flame synthesis the processes of spray formation and evaporation of the single droplets greatly affect the morphology and size of particles formed. An in situ measurement of these parameters is thus essential for process control and development. In this work, wide-angle light scattering (WALS) is applied to measure droplet sizes in a spray flame. The scattering data of the spherical droplets

This paper presents experiment and analysis on variation of temperature sensitivity of resonant modes of a long period grating (LPG) with change in temperature. The theoretical analysis explains the corresponding experimental data on temperature sensitivity of LPGs written in house in Ge-B codoped and H2-loaded telecom fiber. The LPGs were first annealed for thermal stability. The average temperature

We introduced a theoretical model to preserve the quality and the efficiency of a picosecond second-harmonic generation (SHG) in a 30-mm-long LBO crystal which is surrounded by a thermal oven. It is proposed to arrange a temperature gradient throughout the crystal length for mitigating the undesirable consequences of dispersion and group velocity mismatch. To optimize the pulse shape, a distance parameter

It is a key procedure of measuring the diode laser wavelength in the wavelength modulation spectroscopy (WMS) technique since it determines the selection of specific modulation amplitude and frequency and thus the overall accuracy of the WMS technique. However, the wavelength modulation frequency of lasers is usually from tens of kHz to hundreds of kHz, which makes the traditional methods difficult

We present results on the lasing properties of the Bi-doped high-germania glass fibers thermally treated at different heating and cooling conditions. The absorption and luminescence spectra, the luminescence lifetime of bismuth-related active centers (BACs) formed in the Bi-doped fibers before and after treatment were measured. Analyzing the results, it was shown that the concentration of the BACs

Present-day laser-spectroscopy experiments increasingly rely on modern commercial devices to monitor, stabilize, and scan the wavelength of their probe laser. Recently, new techniques are capable of achieving unprecedented levels of precision on atomic and nuclear observables, pushing these devices to their performance limits. Considering the fact that these observables themselves are deduced from

Wavelength meters are widely used for frequency determinations and stabilization purposes since they cover a large wavelength range, provide a high read-out rate and have specified accuracies of up to \(10^{-8}\). More accurate optical frequency measurements can be achieved with frequency combs but only at the price of considerably higher costs and complexity. In the context of precise and accurate

We report a technologically novel microscopy system for bioimaging based on a 100 fs titanium:sapphire (Ti:Sa) laser pumped coherent continuum from a tailored, 9-cm long, all normal dispersion (ANDi) fiber, enabling concurrent image contrast with (a) spectral focusing coherent anti-Stokes Raman scattering (SF-CARS) (spanning 900–3200 cm−1) and (b) sum frequency generation (SFG). Both modalities were

We employed a hybrid femtosecond/picosecond coherent anti-Stokes Raman scattering (fs/ps CARS) instrument to probe rotational temperatures of molecular hydrogen in the multiphase reaction zone of an aluminized ammonium perchlorate (AP) propellant flame. Significant concentrations of hydrogen, present in the plume due to the decomposition of the propellant binder material and subsequent reactions with

We have compared two kinds of dispersive mirrors (DMs) produced by magnetron sputtering and ion beam sputtering. One of them is a broadband DM which is known as double-angle DM, providing a group delay dispersion (GDD) of \(-40 \mathrm{{fs}}^2\) in the range of 550–1050 nm. The other one is a robust highly dispersive mirror, which provides a GDD of about \(-275 \mathrm{{fs}}^2\) at 800 nm and covers

Abstract A low-index polymer-overlaid micro-resonator (LIMR) with high sensitivity is investigated for simultaneous temperature and ambient refractive index (ARI) measurement. The sensitivity of the proposed LIMR to the ambient index is remarkably enhanced at the turning points of the dispersion curve. After examining the optical spectrum of the proposed LIMR sensor, we assess two typical configurations

Abstract We present a numerical analysis of the polarization-insensitive squared spiral-shaped graphene-based tunable metasurface for the high performance of the reflection control. The proposed structure is investigated for the normal and complementary behavior of the graphene surface. The proposed metasurface structure is tuned by applying external biasing potential which will ultimately control

Abstract A critical evaluation of the experimental and theoretical literature regarding the rates for fine structure mixing in the first excited 2P3/2,1/2 states of potassium and rubidium induced by collision with 4He is performed. The evaluation is used to develop a recommendation for the fine structure mixing rates as a function of temperature. The rate coefficient for transitions from Rb 5 2P3/2

Abstract The hollow flat-topped Gaussian beam (HFTGB) is proposed to describe the flat light ring beams. The analytical formula for the propagation of HFTGB through any ABCD system is obtained based on the expansion of hollow Gaussian beams. Based upon this formula, the propagation characteristics of HFTGB are investigated in detail. It is found that both 3D bright spot and dark spot exist in the propagating

Abstract In this paper, a new phase retrieval method using sequential phase modulations is proposed. Behind the unknown object, adding sequential phase modulations will change the diffraction intensities received by sensor. Through increasing the number of diffraction intensities patterns, the difficulty of retrieving the unknown object is decreased. To better select these modulation phases, the complexity

Abstract Controllable continuous-wave dual-wavelength laser operation of a Nd:GdVO4/Nd:YVO4 composite crystal at 1063 and 1064 nm was demonstrated using in-band diode pumping around 912 nm. The spectral power ratio of the two laser wavelengths could be adjusted simply by controlling the pump wavelength of the laser diode via temperature. The laser produced the maximum total output power of 4.48 W.

Abstract The dynamics of light bullets propagating in nonlinear media with linear/nonlinear, gain/loss and coupling described by the (2+1)-dimensional vectorial cubic–quintic complex Ginzburg–Landau (CGL) equations is considered. The evolution and the stability of the vector dissipative optical light bullets, generated from an asymmetric input with respect to two transverse coordinates x and y, are

Abstract High-pulse repetition rate lasers allow significant enhancement in the average power of the low-order harmonics generation in isotropic media. We report on the third (343-nm) and fifth (206-nm) harmonics generating in air and different nanoparticle-containing laser-produced plasmas by applying Yb-doped fiber laser delivering 37-fs, 100-kHz, 1030-nm, 0.5-mJ pulses. Different characteristics

Abstract Atoms trapped in the evanescent field around a nanofiber experience strong coupling to the light guided in the fiber mode. However, due to the intrinsically strong positional dependence of the coupling, thermal motion of the ensemble limits the use of nanofiber trapped atoms for some quantum tasks. We investigate the thermal dynamics of such an ensemble using short light pulses to make a spatially

Abstract The authors report on the performance and scalability of a Q-switched, cryogenically cooled Ho:YAG laser. The Ho:YAG slab was resonantly pumped using a continuous wave thulium fibre laser, and the output energy from the oscillator was extracted using a confocal resonator with a single-pass pump geometry, resulting in 135 mJ at 200 Hz with a beam quality of M2 < 1.14 and a slope efficiency

Abstract Magnetically trapped \(^{87}\)Rb atoms have been observed near a single-mode optical nanofibre. Approximately \(1\times 10^6\) atoms were optically pumped to the \({|{F=2,m_\mathrm{F}=2}\rangle }\) state and held in the trap with a trap lifetime of up to 2 s. The temperature of the atomic sample within the magnetic trap was measured to be below \(230\,\upmu \hbox {K}\). The compact vacuum

Abstract Generally, resonant optical gyroscopes (ROG) based on the Sagnac effect are very sensitive to the changes of temperature and optical power, which directly affects the output of the gyroscope. To improve the frequency lock-in accuracy and thermal stability of ROG system, the technology of laser frequency combination tuning and locking is proposed and experimentally demonstrated. Using the characteristics

Abstract Grating waveguide structures (GWS) are reflective diffractive optical elements that operate based on the combination of sub-wavelength gratings (periodic microstructures) integrated with planar waveguides. They can be used for high-power laser applications for pulse compression, spectral stabilization, wavelength multiplexing, as well as polarization shaping. In this work, we investigate the

Abstract We discuss photo-luminescence characteristics of CdSe core/shell quantum dots at cryogenic temperatures using a hybrid system of a single quantum dot and an optical nanofiber. The key point is to control the emission species of quantum dot to charged excitons, known as trions, which have superior characteristics to neutral excitons. We investigate the photocharging behavior for the quantum

Abstract In this paper, an ultra-thin microwave absorber with cross-resonator (CR) exhibiting a broad absorption bandwidth is designed and fabricated. Theoretical and experimental results show that the absorber has a wideband strong absorption in a frequency range from 2.2 to 6.8 GHz and from 2.2 to 5.4 GHz when incident electric field is y-and x-polarized, respectively. The equivalent L–C circuit

Abstract The orbital angular momentum (OAM) of the vortex beam has infinite dimension and are orthogonal to each other. OAM multiplexing technology is one of the key technologies to improve the channel capacity of wireless optical communication system. When the vortex beams propagate in atmospheric turbulence, it will cause wavefront distortion. The phase diversity (PD) method is used to obtain the

Abstract In this paper, the quality assessment of isogams is demonstrated by laser-induced breakdown spectroscopy (LIBS) using the comparative standardization method. Here, the mass concentrations of carbon and hydrogen, as basic elements of tar, relative to that of calcium, as an undesired element, are taken into account as principal parameters to determine the quality of isogams. Hence, the intensity

Abstract Photoacoustic spectroscopy is a highly sensitive technique, well suited for and used in applications targeting the accurate measurement of water vapor in a wide range of concentrations. This work demonstrates the nonlinear photoacoustic response obtained for water vapor in air at typical atmospheric concentration levels, which is a result of the resonant vibrational coupling of water and oxygen

Abstract The broadening of the oxygen absorption line P9P9 due to wall collisions of entrapped oxygen gas in nanoporous solid discs of average pore diameters between 70 and 150 nm is studied using GAs in Scattering Media Absorption Spectroscopy (GASMAS) method. A model based on the kinetic theory of gasses is used to find a correlation between the wall-collision broadening and the average pore diameter

Abstract We present new high-resolution absorption data for the important sesquioxide laser material Yb:Lu2O3 for the spectral range of 880–1020 nm, at various temperatures between 8 and 300 K, and for the zero-phonon region from 960 to 990 nm, at temperatures from 8 to 300 K. We have experimentally observed the C3i (0,1)–(1,3) transition for the first time, located at 880.7 nm at 8 K. Based on high

We present on THz generation in the two-color gas plasma scheme driven by a high-power, ultrafast fiber laser system. The applied scheme is a promising approach for scaling the THz average power but it has been limited so far by the driving lasers to repetition rates up to 1 kHz. Here, we demonstrate recent results of THz generation operating at a two orders of magnitude higher repetition rate. This

Mosquito-borne diseases are a major challenge for Human health as they affect nearly 700 million people every year and result in over 1 million deaths. Reliable information on the evolution of population and spatial distribution of key insects species is of major importance in the development of eco-epidemiologic models. This paper reports on the remote characterization of flying mosquitoes using a

A systematic study of laser-induced thermal-grating scattering (LITGS) using nitric oxide as an absorbing species is presented as a means of thermometry in air-fed combustion. The relative contributions to the scattered signal from degenerate four-wave mixing, DFWM, and from laser-induced thermal-grating scattering, LITGS, are studied in the time domain for NO in N2 buffer gas up to 4 bar, using a

We present an experimental technique to determine the degenerate two-photon absorption (2PA) spectra by performing a single Z-scan using a high-spectral-irradiance white light continuum (WLC) generated by a hollow core fiber. The hollow fiber was filled with Argon (Ar) gas at a pressure of 0.6 bar and was pumped with 500 mJ, 30 fs, and 800 nm pulses. The broadband WLC pulses with 350 nm bandwidth in

Long-wavelength mid-infrared (MIR) frequency combs with high power and flexible tunability are highly desired for molecular spectroscopy, including investigation of large molecules such as C60. We present a high power, phase-stabilized frequency comb near 10 μm, generated by a synchronously pumped, singly resonant optical parametric oscillator (OPO) based on AgGaSe2. The OPO can be continuously tuned

We report the second harmonic generation and fourth harmonic generation of the output from a short-pulsed (~ 80 ps) thulium-doped fiber laser, generating 976 and 488 nm wavelengths with high efficiency. With a narrow-linewidth (0.5 nm) pump at a power of 3.2 W, a second harmonic power of 2.4 W was generated at 976 nm with a conversion efficiency reaching 75%. For FHG, 690 mW of power at 488 nm was