Modulation format identification (MFI) is an indispensable part of next generation optical networks such as elastic optical networks (EON). We propose a simple MFI method based on signal amplitude sorting and ratio calculation. After sorting the amplitude of signals, three MFI feature values are extracted to identify polarization division multiplexing (PDM) quadrature phase shift keying (PDM-QPSK)

We develop a novel method for fabricating borosilicate millibubble resonators with strong thermo-optical effect. The method is based on self-expanding of air within a two ends sintered borosilicate capillary under the heating of a hydrogen-oxygen flame (HOF). The intrinsic thermo-optical effect of borosilicate millibubble resonator is experimentally demonstrated by a designed novel structure based

An all-optical fiber modulator with a graphene interlayer is proposed and calculated numerically. Graphene has excellent optical characteristics such as wide optical bandwidth, ultra-fast response and zero band gap, which makes the modulator cover the whole C and S band. Modulation rate is only limited by the inherent carrier relaxation time of graphene. We also deduced the mechanism of all-optical

We investigate the characteristics of the error surface shape (ESS) induced by spatial attitude variations (SAVs) of the tested surface in the phase measuring deflectometry (PMD) system. In a PMD system, the spatial attitude of the target mirror might deviate from its initial status due to the instability and the stress release of the assembly structure. According to the principle of the PMD, there

This paper proposes and analyzes a parity-time (PT) symmetry structure based on resonant optical tunneling effect (ROTE) by using two directly coupled ROTE resonators to achieve a balanced gain-loss distribution. The unbroken/broken states of the PT symmetric system are theoretically verified by coupled-mode theory (CMT), transmission matrix method (TMM) and finite-difference time-domain (FDTD). To

This paper presents a hyperspectral imaging approach using a single-pixel detector. The system consists of a two-stage encoding system based on the concept of Hadamard transformation. In contrast with conventional hyperspectral imaging method where wavelength filters or Fourier spectroscopy is usually adopted, the spectral imaging system in this design uses an encoded slit, a resonant scanning mirror

The hollow Gaussian beam can be generated by thermal lens effect for a Gaussian beam propagating through a medium with finite optical absorption. The new model of hollow Gaussian beam (HGB) is proposed by the effective thermal focal length at steady state. The transformation between the HGB and quasi-hollow beam is achieved by tunable input power. Based on the experimental and numerical analysis, the

A highly flexible and efficient method of generating stable radially and azimuthally polarized perfect optical vortex beams and all higher order cylindrical perfect vector vortex beams is proposed and demonstrated. The method is the most convenient implementation of the coherent superposition of two orthogonally circularly polarized optical vortex beams of arbitrary integer topological charges. The

We propose an optically controlled scheme to generate a multi-carrier PSK (phase-shift-keying) signal by using cross-polarization modulation (XPolM) in a highly nonlinear fiber (HNLF). A main advantage of our approach is all-optical multi-carrier PSK signal generation, which is promising for uninterrupted transmission and seamless connection of signal to different remote stations by fiber transmission

The residual linear birefringence inside the sensing coil is one of the main factors causing polarization error and accuracy decline of a fiber optic current sensor. To relieve the residual linear birefringence in fiber optic current sensors, a chiral photonic crystal fiber was utilized as the sensing coil, whose air filling ratio, lattice constant and chiral parameter were designed according to the

Optical pumping is a process that produces a nonthermal Zeeman sublevel population distribution. It plays an important role in alkali-metal magnetometers for two uses, constructing the sub-Doppler features to lock the laser frequency and providing the spin-polarized atoms to precess around the magnetic field. To comprehensively study the properties of sodium (Na) magnetometer, we present the detailed

A novel mode division multiplexer with low loss, low crosstalk is proposed for a type of few mode ring-core fiber (FM-RCF) in our paper. A novel FM-RCF with pure silica ring-core and larger effective refractive index difference (>1×10−3) between the modes is proposed as mode transmission channel of our multiplexer. The ring-core channel structure and the larger effective refractive index difference

We study the electromagnetically induced transparency (EIT) phenomenon in a hollow-core fibre filled with rubidium gas. We analyse the impact of the guiding effect and of the temperature on the properties of the EIT phenomenon. The refractive index felt by the probe laser is found to vary due to the radial dependence of the fibre mode field at the pump frequency. Several results are presented for the

In this paper, we propose an electrically driven optically excited laser structure for terahertz (THz) generation in quantum cascade lasers (QCLs) through frequency down-conversion optical nonlinearity. In our distinct design, both the pump and THz radiations are generated simultaneously by optical and electronic intersubband transitions (ISTs) between the quantized states within the conduction band

This work studies the transmission dynamics of self-similar optical beams through an inhomogeneous tapered graded-index waveguide under diffraction and nonlinearity management as well as self-frequency shift arising from stimulated Raman scattering (SRS). A similarity transformation connecting with the constant-coefficient higher-order nonlinear Schrö dinger’s equation (HNLSE) is employed to construct

A novel scheme based on the cascade structure of a dual-polarization Mach–Zehnder modulator (DPol-MZM) and a phase modulator (PM) is proposed which can simultaneously identify the value and direction of Doppler frequency shift (DFS). A low frequency reference signal and an echo signal are modulated by the DPol-MZM into orthogonal polarization states. The transmitted signal is modulated onto the reference

A three-layer complementary strip Dirac semimetal polarizer is proposed to achieve polarization rotation, perfect polarization conversion, and asymmetric transmission. This device can realize broadband polarization operation of linear polarized waves in the terahertz frequency domain. By changing the Fermi level of the Dirac semimetal, the polarization angle of linearly polarized light in the frequency

In this paper, we have proposed an analytic model and determined the outage probability and average bit error rate (BER) performance of a co-operative radio frequency – underwater wireless optical communication (RF–UWOC) system. In recent years, UWOC has attracted attention as a useful enabler of underwater activities such as climate and ocean monitoring, surveillance, ocean exploration, underwater

Distinctively narrow and asymmetric line shape Fano resonances arise due to resonant interactions of sub-radiant and super-radiant modes in plasmonic nanostructures and metamaterials. A number of recent experimental studies have shown unique opportunities provided by highly dispersive Fano resonances in biosensing applications. However, there is limited understanding of Fano resonant optical response

We present a hyperspectral imager with a dual disperser architecture, which is highly re-configurable thanks to the use of a digital micro-mirror device (DMD). The system has over 200 spectral bands in the range 400 - 700 nm, and 2048 by 2048 spatial pixels. We describe a method to calibrate the instrument and quantify its performance using a simple slit scanning acquisition scheme, and discuss various

An out-of-band suppression improved microwave photonic Hilbert transformer (MPHT) with adjustable bandwidth and central frequency based on optical spectral shaping is theoretically analyzed and experimentally demonstrated. The MPHT consists of a broadband optical source, a Mach–Zehnder interferometer (MZI), a dispersion compensating fiber and a photodetector. The MZI incorporates an intensity modulator

For traditional integral imaging display systems with usual lens array, there is the same viewing angle in the horizontal and vertical direction. Due to usual display has vertically long sub-pixels, this sub-pixel shape makes the view density be lower in vertical direction than the horizontal one. Here, a clear full-parallax 3D light field display with uniform view density along the horizontal and

High-order harmonic generation in solid state materials is viewed as a means of studying strong field nonperturbative physics. Researching ellipticity dependence can help understand the dynamics of electron–hole pairs in the presence of strong laser field. In this work, ellipticity dependence of high harmonic generation in few layer MoS2 is experimentally investigated with a midinfrared laser centered

It is inherently difficult for a conventional microscopic imaging system to produce images with both wide field of view (FOV) and high-resolution because of its limited space bandwidth product. Fourier ptychographic microscopy (FPM) has been developed to overcome this limitation by using angle-varied illumination to enhance the performance of the system. In this paper, we propose a FPM imaging approach

We present numerical and experimental study on the origin of fluctuations in the idler power in partially degenerate intermodal four wave mixing in a 1 km long few mode graded index fiber where both the fundamental and higher order modes are excited in both pump and signal wavelengths. Numerical simulation is carried out in the presence of different types of mode coupling processes and group delay

The ternary optical computer (TOC) has the characteristics of numerous bits, bit-wise allocation, bit function reconstruction, parallel calculation, and easy extension of the processor. With the successful running of the adder on a 192-bit prototype system SD16 (an abbreviation of Shanghai Daxue’s machine 2016) of the TOC in Shanghai University, the theory and technology of the reconfigurable optoelectronic

The development and the ability of an optical integrated polymeric resonator, acting as a surface light probe, for monitoring temperature-induced supramolecular phase transitions is presented in this work. The homogeneous detection of the transitions between different self-assembled structures in an aqueous solution of fatty acids (12-hydroxystearic acid, in association with amino-pentanol) was studied

The cylindrical vector beams (CVBs) as the spatially orthogonal modes in fiber provide additional degree of freedom for optical fiber communication. The ring-core fibers with a high refractive index area matching with the beam shape of CVBs are suitable for stable transmission of CVBs. We simulate and experimentally characterize the CVBs transmission in ring-core fibers with different geometric structure

With the increase in free-space optical communication distance and link attenuation, photon-counting communication based on a single photon detector will be the development trend in the future. In this paper, we use a single-pixel single photon avalanche diode (SPAD) detector to study the bit error rate (BER) performance of photon counting communication. As the single-pixel SPAD cannot distinguish

The theoretical description and experimental demonstration for pressure sensing characterized over the spectrum shift of FBG and exponential property are reported, which are investigated through the system of an optical fiber loop ring-down cavity (FLRDC) inserted a fiber Bragg grating (FBG). The mathematical models and simulations of FLRDC-FBG are established to investigate the exponential equation

One of the key tasks in designing off-axis optical systems is to place freeform surfaces in optimal locations. By analyzing the real ray paths, we introduce one simple method for locating freeform surfaces in off-axis systems. A four mirror off-axis microscope objective with freeform surfaces is designed to demonstrate the method, the result shows that our method is effective in identifying the optimal

Next significant revolution of virtual/augmented reality and Internet of things show the remarkable demands of next-generation indoor mobile real-time data transmission are high spectral-efficiency, high-speed and high-density deep coverage. Multi-color visible light communication (MC-VLC) has remarkable potential to confront the challenges due to the large equivalent bandwidth index and extensively

We firstly explored lasing properties of a 2.1μm Ho laser intra-cavity pumped by a diode-pumped Tm:YVO4 laser, which has a large absorption cross-section and broad absorption profile at 800 nm. Maximum output power of 1.42 W at 1908 nm was obtained before Ho laser with a 2 mm long Tm:YVO4 crystal under absorbed common 808 nm LD power of 9.96 W. High reflection coating the output couplers at Tm laser

Visible light communication (VLC) is one of the promising technologies for future wireless communications and has attracted increasing research interest in recent years. In this paper, we propose an adaptive least squares (LS) channel estimation algorithm for VLC systems using the direct current biased optical orthogonal frequency division multiplexing (DCO-OFDM) scheme. The proposed algorithm is obtained

Using an acousto-optic modulator of zero-order transmission as the Q-switch, single-frequency laser pulses were obtained in a ring cavity fiber laser with the seed injection technique. The acousto-optic modulator avoided the frequency-shift resulting from the RF driver signal in the first-order transmission. As the seed laser, a distributed-feedback fiber laser based on the π phase-shift fiber Bragg

In this paper, a carboxymethyl cellulose (CMC)/carbon nanotubes (CNTs) composite film was manufactured and used as a good humidity sensitive material to design a humidity and temperature simultaneous measurement sensor with simple structure, high sensitivity and fast response time. The sensor is constructed by a fiber Bragg grating (FBG) and then connected a hollow-core fiber (HCF) on the end face

In this paper, a method for increasing the temporal resolution of a temporal imaging system has been developed. Analogously to the conventional spatial imaging systems in which resolution limit is due to the finite aperture of the lens, in a temporal imaging system, the finite temporal aperture of the time lens is responsible for limited temporal resolution. Based on the method used in spatial structured

In the past few years, visible light communication (VLC), which uses solid-state lightings to transmit information, has been regarded as an emerging way of wireless communication technology. For the combination of illumination and communication, dimming control is a necessary function for VLC systems. Traditional dimming control binary-based dimming schemes are spectral inefficient, while most of the

Holographic Predictive Search (HPS) is a novel approach to search-based hologram generation that uses a mathematical understanding of the optical transforms to make informed optimisation decisions. Existing search techniques such as Direct Search (DS) and Simulated Annealing (SA) rely on trialling modifications to a test hologram and observing the results. A formula is used to decide whether the change

In this letter, two novel hollow-core photonic crystal fibers (PCFs) are proposed, simulated, and analyzed. The PCFs stably support Orbital Angular Momentum (OAM) transmission. These PCFs are theoretically and systematically investigated, discussed, and compared their properties, structures, and parameters. Besides, an effect of core size and pattern of air holes on OAM parameters is investigated with

Fourier single-pixel imaging (FSPI) technique can encode a real two-dimensional scene to one-dimensional time-varying light intensity sequences traveling in the free space. In this work, FSPI with weighted light source is regarded as a carrier of multi-dimensional information while capturing the object scene using a lens-free photodetector, and can carry visible and invisible optical information simultaneously

An image pan–tilt system with a flat shape and a large aperture is proposed based on a symmetric integral imaging system. The proposed system comprises five lens arrays and two actuators. The image pan–tilt function is performed by shifting the two lens arrays located at the entrance side using two actuators. The displacements of the two lens arrays are less than one lens pitch; hence, the pan–tilt

Sampling frequency offset between digital-to-analog converter (DAC) and analog-to-digital converter (ADC) always exists in asynchronous optical discrete multi-tone (DMT) systems. The overall bit error rate (BER) performance may be seriously deteriorated due to SFO-induced phase rotation. Inter-symbol differential encoding/detection (ISDE/ISDD) with decision-aided residual phase compensation (RPC) has

A temperature and humidity sensor based on photonic crystal fiber(PCF) coated with graphene oxide (GO) cascaded with two spherical structures is presented and demonstrated. The principle of this sensor is based on Mach-Zender interferometer (MZI), and the interference spectrum is sensitive to the change of temperature and humidity. Because of the hydrophilic property of GO, refractive index (RI) of

Precoding technique is proposed and experimental demonstrated to resist sampling frequency offset (SFO) in W-band OFDM RoF systems. Walsh-Hadamard transform (WHT)-precoding, discrete Hartley transform (DHT)-precoding, Zadoff-Chu transform (ZCT)-precoding, and orthogonal circulant matrix transform (OCT)-precoding are investigated and compared. SFO-induced inter-carrier interference (ICI) on each subcarrier

This paper reports the extension of vectorial complex ray model allowing to account, in the high-frequency limit, for the direction, polarization, curvature of wave front, amplitude, phase and scattering intensity of the light rays interacting with an infinite cylinder of arbitrary while smooth cross section. Based on the proposed method, a numerical study is performed on the scattering patterns of

An adaptive square-root unscented Kalman filter with a parallelized architecture for carrier recovery is proposed in QPSK based satellite-to-ground coherent optical communication systems. A new observation model is raised in the proposed scheme to make the state estimation more accurate. The process noise covariance (Q) and the measurement noise covariance (R) are adaptively estimated to make them

We report the saturation spectroscopy of carbon dioxide inside a hollow glass waveguide (GW) using a tunable mid-infrared difference frequency generation (DFG) source. This DFG source was generated in a periodically poled lithium niobate crystal with a tuning range from 3.97 to 4.71μm. Saturated spectroscopy was performed on the R(60) transition of CO20001 ← 0000 band at 4.2μm inside a hollow GW of

In optical networks for telecom and datacom, an unprecedented energy efficient system is demanded since the amount of data traffic is rapidly increasing while a significant improvement of the energy efficiency in electronics devices such as switch ASICs is no longer expected. To overcome the energy constraints, introduction of energy-efficient optical circuit switching (OCS) to the conventional electrical

A surface plasmon resonance (SPR) refractive index (RI) sensor based on a D-shaped Hi-Bi photonic crystal fiber (PCF) is investigated with finite element method. Through changing the asymmetry of the fiber core along x- and y- axis, it is found that the Hi-Bi structure can greatly enhance the plasmon resonance at near-infrared wavelength, thus effectively reducing the FWHM. Benefiting from this, the

We numerically investigate the statistical characteristics of mode couplings induced by concatenated multiple few-mode fiber connections with lateral misalignments in weakly-coupled mode division multiplexed (MDM) systems. For the currently-feasible connectors, the probability of the crosstalk ratio being smaller than -20 dB is remarkably degraded as increasing the number of the connections. The currently-feasible

A global positioning system (GPS) with high positioning accuracy (PA) is not feasible for challenging environments such as tunnels, underground, complex buildings, etc. For such environments, the alternative technology of visible light positioning (VLP) system has emerged as a viable solution. In this paper, we propose for the first time, a hybrid multi-band carrier-less amplitude and phase (m-CAP)

Multiscale micro/nano structures (e.g. large period ripples and sputtered particles) on titanium surfaces by obliquely incident femtosecond laser texturing. The effects of laser incident angle on surface structures, wettability and structural color were studied. As a result, sputtered particles are formed on the titanium surface for all incident angle. Fine ripples are appeared on the large period

The tailoring of the electromagnetic wave plays a more and more critical role in various fields, such as infrared detection, invisibility, and telecommunication. Nowadays, the requirement for dual- and wide-band tailoring is more and more intense. In order to achieve infrared stealth property in addition to possessing the ability of radiative cooling, a composite periodic structure is proposed to meet

In this paper we extend the concept of perfect optical vortex to the vector case and investigate its focusing properties in the high numerical aperture regime. We show that simultaneous phase encoding of orthogonal components can be realized by means of a 4f imaging system incorporating a phase only liquid-crystal spatial light modulator whose director axis is rotated 45° with respect to the horizontal

The trade-off relationship of the angular reconstruction rate and spatial reconstruction rate of the light field display system is further analyzed by taking the limited optical field of view of the lens into consideration. The comparison of the number of the perspectives and resolution of each perspective of the rectangular arranged lens array and the hexagonal arranged lens array is made, showing

Achieving simultaneous controls of the amplitude and phase for electromagnetic waves is essential when shaping a complete wave-front aimed at forming an arbitrary beam. Here a strategy of manipulating the reflected amplitude and phase is proposed using a bi-layered metasurface element. The metasurface unit cell, consisting of a modified I-shape particle and one all-metal ground, achieves broadband

The focus of this study was mainly on the birefringence of nanosized bowtie-shaped slot core fibers that can transport ultrasmall optical spots. Here we showed large birefringence for the fibers reaching as high as 0.33, which is three orders of magnitude greater than normal-sized birefringent fibers, the main cause of which being the impact of geometrical birefringence arising from significant differences

The traditional method for calculating laser induced damage threshold (LIDT) value of thin films is based on qualitative or semi-quantitative empirical formulas, the results obtained are of low accuracy and credibility. A new method for accurately calculating LIDT values of thin films is presented in this paper, when a thin film is subjected to intense laser irradiation, the distribution models of

A method for judging the locations of dynamic stable zones boundaries and mode separations is presented by spherical aberration “transient variation” Experiments on spherical aberration in dynamic stable zones of an end-pumped laser are carried out. Based on the inversion of the wavefront information, the ”beam quality deterioration zone” is investigated. The multiple relationships among the thermal