Determining the mass of a vehicle from ground-based passive sensor data is important for many traffic safety requirements. This work presents a method for calculating the mass of a vehicle using ground-based video and acoustic measurements. By assuming that no energy is lost in the conversion, the mass of a vehicle can be calculated from the rotational energy generated by the vehicle’s engine and the linear acceleration of the vehicle over a period of time. The amount of rotational energy being output by the vehicle’s engine can be calculated from its torque and angular velocity. This model relates remotely observed, engine torque-induced frame twist to engine torque output using the vehicle’s suspension parameters and engine geometry. The angular velocity of the engine is extracted from the acoustic emission of the engine, and the linear acceleration of the vehicle is calculated by remotely observing the position of the vehicle over time. This method combines these three dynamic signals; engine induced-frame twist, engine angular velocity, and the vehicle’s linear acceleration, and three vehicle specific scalar parameters, into an expression that describes the mass of the vehicle. This method was tested on a semitrailer truck, and the results demonstrate a correlation of 97.7% between calculated and true vehicle mass.

Vehicle detection is an important topic for advanced driver-assistance systems. This paper proposes an adaptive approach for an embedded system by focusing on monocular vehicle detection in real time, also aiming at being accurate under challenging conditions. Scene classification is accomplished by using a simplified convolution neural network with hypothesis generation by SoftMax regression. The output is consequently taken into account to optimize detection parameters for hypothesis generation and testing. Thus, we offer a sample-reorganization mechanism to improve the performance of vehicle hypothesis verification. A hypothesis leap mechanism is in use to improve the operating efficiency of the on-board system. A practical on-road test is employed to verify vehicle detection (i.e., accuracy) and also the performance of the designed on-board system regarding speed.

The linear canonical transform (LCT) is used in modeling a coherent light-field propagation through first-order optical systems. Recently, a generic optical system, known as the quadratic phase encoding system (QPES), for encrypting a two-dimensional image has been reported. In such systems, two random phase keys and the individual LCT parameters (α,β,γ) serve as secret keys of the cryptosystem. It is important that such encryption systems also satisfy some dynamic security properties. We, therefore, examine such systems using two cryptographic evaluation methods, the avalanche effect and bit independence criterion, which indicate the degree of security of the cryptographic algorithms using QPES. We compared our simulation results with the conventional Fourier and the Fresnel transform-based double random phase encryption (DRPE) systems. The results show that the LCT-based DRPE has an excellent avalanche and bit independence characteristics compared to the conventional Fourier and Fresnel-based encryption systems.

We propose an effective and efficient method that reduces the crosstalk level in autostereoscopic light-emitting diode (LED) displays by optimizing the pixel arrangement of the associated two-dimensional (2-D) LED panel. In the proposed method, first a series of parallax barrier patterns, based on predesignated LED packaging units, are designed and simulated by sequentially regulating the width of black stripes on the 2-D LED panel. This design principle removes the black stripes from conventional autostereoscopic LED display pixels for optimal parallax barrier calculation. Furthermore, the mathematical relationship between average crosstalk level and visual flux density is obtained from the simulation. A mathematical fitting method that includes a cubic fitting function is finally applied to achieve proper pixel arrangement in the 2-D LED panel. The simulation results obtained for a dual viewpoint autostereoscopic LED display system indicate that the most suitable value for the width of the black stripes is within the range of 3.17604 to 3.34277 mm, with a light-emitting pixel width of 2 mm. This method can effectively guide the 2-D LED panel’s design and result in high performance autostereoscopic three-dimensional LED displays, which will have broad application prospects in the near future.

A high-resolution computer-generated stereogram for forming full-parallax three-dimensional (3-D) images is proposed. A full-parallax 3-D image is formed from 825 two-dimensional (2-D) projections and can be observed in a wide angular range. The stereogram is a reflective diffractive optical element (DOE) that consists of 50×50  μm2 hogels, where each hogel corresponds to one pixel of the 2-D frames. A phase-type kinoform is computed in every hogel by solving a nonlinear inverse problem. The DOE relief is fabricated using electron-beam technology with pixel size of 0.2×0.2  μm2. The effectiveness of the technology developed is illustrated by photographs and a video of a real DOE under monochromatic light and under white light. The new high-resolution full-parallax stereograms can be used for protecting bank notes, documents, and ID cards against counterfeit.

This all-in-one hiding method creates two transparencies that have several decoding options: visual decoding with or without translation flipping and computer decoding. In visual decoding, two less-important (or fake) binary secret images S1 and S2 can be revealed. S1 is viewed by the direct stacking of two transparencies. S2 is viewed by flipping one transparency and translating the other to a specified coordinate before stacking. Finally, important/true secret files can be decrypted by a computer using the information extracted from transparencies. The encoding process to hide this information includes the translated-flip visual cryptography, block types, the ways to use polynomial-style sharing, and linear congruential generator. If a thief obtained both transparencies, which are stored in distinct places, he still needs to find the values of keys used in computer decoding to break through after viewing S1 and/or S2 by stacking. However, the thief might just try every other kind of stacking and finally quit finding more secrets; for computer decoding is totally different from stacking decoding. Unlike traditional image hiding that uses images as host media, our method hides fine gray-level images in binary transparencies. Thus, our host media are transparencies. Comparisons and analysis are provided.

We propose a method to suppress the speckle noise in holographic display using time multiplexing. The diffractive optical elements (DOEs) and the subcomputer-generated holograms (sub-CGHs) are generated, respectively. The final image is reconstructed using time multiplexing of the subimages and the final subimages. Meanwhile, the speckle noise of the final image is suppressed by reducing the coherence of the reconstructed light and separating the adjacent image points in space. Compared with the pixel separation method, the experiments demonstrate that the proposed method suppresses the speckle noise effectively with less calculation burden and lower demand for frame rate of the spatial light modulator. In addition, with increases of the DOEs and the sub-CGHs, the speckle noise is further suppressed.

Automatic target recognition (ATR) is a traditionally challenging problem in military applications because of the wide range of infrared (IR) image variations and the limited number of training images. IR variations are caused by various three-dimensional target poses, noncooperative weather conditions (fog and rain), and difficult target acquisition environments. Recently, deep convolutional neural network-based approaches for RGB images (RGB-CNN) showed breakthrough performance in computer vision problems, such as object detection and classification. The direct use of RGB-CNN to the IR ATR problem fails to work because of the IR database problems (limited database size and IR image variations). An IR variation-reduced deep CNN (IVR-CNN) to cope with the problems is presented. The problem of limited IR database size is solved by a commercial thermal simulator (OKTAL-SE). The second problem of IR variations is mitigated by the proposed shifted ramp function-based intensity transformation. This can suppress the background and enhance the target contrast simultaneously. The experimental results on the synthesized IR images generated by the thermal simulator (OKTAL-SE) validated the feasibility of IVR-CNN for military ATR applications.

An optical range finder system that relies on laser diodes’ frequency noise, instead of intensity or frequency modulations, and its improvement in resolution are reported. The distance to the target is measured by calculating the cross-correlation of two signals reflected from the target and reference mirrors. These two signals are converted from the laser diodes’ frequency noise signals by frequency/intensity converters, such as a Fabry–Perot etalon. We obtained the distance to the target by checking time lags between the target and reference beams at the highest correlation coefficient. We also measured the change in the correlation coefficient around the peak sampling point by adjusting the reference-path length, achieving a resolving power of ±3  mm.

We present an alternative shape measurement setup based on a one-shot phase-shifting method employing the modulation of polarization and phase grating interferometry. The setup implementation was carried out with a Mach–Zehnder interferometric arrangement and a synchronized system of a pulsed laser and a fast camera. Under the proposed configuration, a test object is illuminated by two beams of circularly polarized light oppositely rotating, coming from the interferometric arrangement. The reflected light is then conduced to a phase grating interferometry system to generate several phase-shifted fringe patterns in one-shot. To show the feasibility of our proposal, we present some experimental results of a retrieved wrapped phase of a test object and analyzed it using a quality-guide phase unwrapping algorithm to obtain the continuous phase.

We propose a laser trapping-based scanning dimensional measurement method for free-form surfaces. We previously developed a laser trapping-based microprobe for three-dimensional coordinate metrology. This probe performs two types of measurements: a tactile coordinate and a scanning measurement in the same coordinate system. The proposed scanning measurement exploits optical interference. A standing-wave field is generated between the laser-trapped microsphere and the measured surface because of the interference from the retroreflected light. The standing-wave field produces an effective length scale, and the trapped microsphere acts as a sensor to read this scale. A horizontal scan of the trapped microsphere produces a phase shift of the standing wave according to the surface topography. This shift can be measured from the change in the microsphere position. The dynamics of the trapped microsphere within the standing-wave field was estimated using a harmonic model, from which the measured surface can be reconstructed. A spherical lens was measured experimentally, yielding a radius of curvature of 2.59 mm, in agreement with the nominal specification (2.60 mm). The difference between the measured points and a spherical fitted curve was 96 nm, which demonstrates the scanning function of the laser trapping-based microprobe for free-form surfaces.

We present a one-dimensional (1-D) imaging technique that uses longitudinal spatial coherence interferometry to encode a scene’s spatial information onto the source’s power spectrum. By spectrally resolving the output using a spectrometer, a channeled spectrum is measured. Fourier transformation of the channeled spectrum yields a measurement of the incident scene’s angular spectrum. The theory is presented to exhibit analogies to conventional Fourier transform spectroscopy of the power spectrum. Experimental validation of the technique is demonstrated, using a Fabry–Perot etalon, for the reconstruction of 1-D sinusoidal and randomly generated angular spectra. Root mean square error between the input and output angular spectra is demonstrated, on average, to be 12.7% and 13.6% for single-frequency and random spectra, respectively.

A method is proposed to retrieve the absolute phase and the color information of isolated objects. A single-composite image in gray levels is projected and its recording is performed using a color camera. The profiles and color information are extracted using Fourier methods.

In cone-beam computed tomography (CBCT) systems based on flat-panel detector imaging, the presence of scatter significantly reduces the quality of slices. Based on the concept of collimation, this paper presents a scatter measurement and correction method based on single grating scan. First, according to the characteristics of CBCT imaging, the scan method using single grating and the design requirements of the grating are analyzed and figured out. Second, by analyzing the composition of object projection images and object-and-grating projection images, the processing method for the scatter image at single projection angle is proposed. In addition, to avoid additional scan, this paper proposes an angle interpolation method of scatter images to reduce scan cost. Finally, the experimental results show that the scatter images obtained by this method are accurate and reliable, and the effect of scatter correction is obvious. When the additional object-and-grating projection images are collected and interpolated at intervals of 30 deg, the scatter correction error of slices can still be controlled within 3%.

Source-mask optimization (SMO) has emerged as a key technique for 7-nm node and beyond in extreme ultraviolet (EUV) lithography. The pupil required by SMO is usually pixelated, with a free choice of intensity per pixel. However, due to the discrete nature of the EUV illumination system, pupil intensity in current EUV SMO must also be discretized. An illumination system with a freeform fly’s eye that is able to generate the pixelated pupil is proposed. Clear apertures of the field facets in the fly’s eye are different from each other so that the intensity of each pixel on the pupil can meet the requirements of SMO. Each of the field facets is constructed with a freeform surface to get the required arc-shaped illuminated area on the reticle. A method integrated with a numerical method and an optimization process is used to design the freeform surface of the field facets. The simulation result of the design for a prescribed freeform pixelated pupil shows that the uniformity on the reticle is 96.4%, and the pupil intensity error is approximated to be 0.035. The results indicate that the system is effective in generating the required freeform pixelated pupil and reducing the restrictions imposed on the SMO process in EUV lithography.

Modern mobile phones contain one or multiple high-resolution camera modules with miniature multielement lenses. Active alignment of the lens and the image sensor is a common process improvement for the integration of mobile phone camera modules to increase manufacturing yields while maintaining high resolution. Active alignment of the image sensor can offer extra degrees of freedom in lens design optimization and thereby help lens designers offer lens designs with high nominal and as-built performance.

Illumination design usually requires the shaping of a specific irradiance distribution from a given light source. For point-like sources or collimated laser beams various methods exist to construct the shape of the refractive and/or reflective surfaces within the optical system. However, for extended sources, an additional feedback or optimization loop is usually required and limitations are not clear. We propose an analysis and design method that includes the source extension from the very beginning. The method is based on phase space mapping of the source radiance distribution onto the target irradiance distribution. We illustrate the method with several examples.

We investigate the performance limits of hybrid imaging systems including annular binary phase masks optimized for depth-of-field (DoF) extension, as a function of the number of rings and the desired DoF range. The mask parameters are optimized taking into account deconvolution of the acquired raw image in the expression of the global performance of the imaging system. We prove that masks with a limited number of rings are sufficient to obtain near-optimal performance. Moreover, the best achievable image quality decreases as the required DoF range increases, so that for a given required image quality, the DoF extension reachable with binary phase masks is bounded. Finally, these conclusions are shown to be robust against different optical system aberrations and models of scene power spectral density. These results are important in practice to decide if annular binary phase masks are the relevant solution for a given imaging problem and for mask manufacturing, since the number and thickness of the rings reachable at affordable cost by technology are generally limited.

A theoretical analysis and a numerical investigation of 3-dB peak-to-average power ratio electrical constant envelope over orthogonal frequency-division multiplexing (OFDM) signals in coherent-detection optical (CO) systems are proposed. A 100-Gb/s optical system is studied to increase the nonlinear tolerance (NLT) to both Mach–Zehnder modulation and optical propagation impairments. Simulation results show that, with 16- and 64-QAM subcarrier modulations, the proposed system outperforms a conventional CO-OFDM system, if an optical modulation index OMI=2.5 and an electrical phase modulation index 2πh=3 are simultaneously adopted. The achieved NLT denoted by a performance gain of 24 dB is attractive after propagation through 1200 km of dispersion-uncompensated standard single-mode fiber, especially for 10-dBm fiber input power and despite the intrinsic bandwidth enlargement of PMs.

A macrobending loss formula for single-mode fibers, which is shown to accurately predict the bend loss of a single-mode fiber with complex or real refractive index coating, is presented. Theoretical simulations and experimental measurements of bend loss in a fiber with nickel coating obtained by chemical plating and acrylate buffer coating are also presented. Agreements between simulations and measurements support the validity of the theoretical formula. Results show that the large imaginary part of the refractive index of the coating can intensify the bend loss oscillation behaviors, which implies that the bent fiber with metal coating can be utilized in fiber-optic devices.

A nonorthogonal amplitude, phase, and frequency modulation (APFM) technique that can increase the transmission capacity of an optical wireless link based on white light-emitting diode (LED) is proposed. It is implemented by the simultaneous use of nonorthogonal frequency shift keying (FSK) and quadrature amplitude modulation (QAM). A white LED-based wireless link using a 64-APFM scheme is constructed to experimentally verify the proposed technique, where the 64-APFM scheme is implemented by the combination of nonorthogonal 4-FSK and 16-QAM. Two more bits per symbol are transmitted using the proposed scheme with the same bandwidth of QAM. No intercarrier interference effect is observed at the 0.02-% frequency spacing (0.001 MHz) for the used RF carrier (5 MHz) because the correlation between the received 64-APFM signal and only one carrier at a time is accomplished with the help of digital signal processing. 6-Mbit/s (1-Msymbol/s) data are successfully transmitted through an optical wireless channel with a limited bandwidth of 1 MHz. This indicates that six bits per symbol can be transmitted using the proposed APFM technique at the same physical bandwidth as 16-QAM.

The transmission capacity of existing optical fiber will reach its physical limitation due to increasing network bandwidth. Recently, space-division multiplexing (SDM) technology has been proposed to increase the fiber transmission capacity. Multicore fiber (MCF) is a strong candidate for SDM transmission, but the intercore crosstalk will be a critical issue with MCF transmission. We make a specific analysis of transmission crosstalk in elastic optical networks. Then, the concept of spare spectrum availability is introduced to accommodate connection requests. Based on it, two different crosstalk-aware routing, spectrum, and core assignment algorithms are presented at different network states. Simulation results show that our proposed scheme improves the spectrum resource utilization and reduces blocking, with a cost of additional algorithm complexity and set-up delay.

An optical data processing and communication system provides enormous potential bandwidth and a very high processing speed, and it can fulfill the demands of the present generation. For an optical computing system, several data processing units that work in the optical domain are essential. Memory elements are undoubtedly essential to storing any information. Optical flip-flops can store one bit of optical information. From these flip-flop registers, counters can be developed. Here, the authors proposed an optical master-slave (MS)-JK flip-flop with the help of two-input and three-input optical NAND gates. Optical NAND gates have been developed using semiconductor optical amplifiers (SOAs). The nonlinear polarization switching property of an SOA has been exploited here, and it acts as a polarization switch in the proposed scheme. A frequency encoding technique is adopted for representing data. A specific frequency of an optical signal represents a binary data bit. This technique of data representation is helpful because frequency is the fundamental property of a signal, and it remains unaltered during reflection, refraction, absorption, etc. throughout the data propagation. The simulated results enhance the admissibility of the scheme.

For single longitudinal-mode lasers, the phase and frequency noises are very important parameters for their applications. The passive self-homodyne technique with an unbalanced Michelson interferometer is demonstrated to measure the phase and frequency noise characteristics. The Michelson interferometer for measurements is composed of a 3×3 optical fiber coupler and two Faraday rotator mirrors. The measurement performance is derived and discussed strictly from the transmission matrix of the coupler. The influence to the demodulation resulting from the asymmetry of the 3×3 optical fiber coupler is eliminated through the derived relationship between the differential phase fluctuation and the interferometer fringes. The technique is utilized to measure the phase and frequency noise features of a distributed feedback fiber laser. Based on the measured frequency noise spectrum, the lineshape, linewidth, and phase-error variance related to the laser coherence are able to be calculated and discussed well.

It is difficult to measure absolute three-dimensional deformation using traditional digital speckle pattern interferometry (DSPI) when the boundary condition of an object being tested is not exactly given. In practical applications, the boundary condition cannot always be specifically provided, limiting the use of DSPI in real-world applications. To tackle this problem, a DSPI system that is integrated by the spatial carrier method and a color camera has been established. Four phase maps are obtained simultaneously by spatial carrier color-digital speckle pattern interferometry using four speckle interferometers with different illumination directions. One out-of-plane and two in-plane absolute deformations can be acquired simultaneously without knowing the boundary conditions using the absolute deformation extraction algorithm based on four phase maps. Finally, the system is proved by experimental results through measurement of the deformation of a flat aluminum plate with a groove.

A second-order fiber interleaving filter that can provide a channel interleaving capability in second-order comb spectra is proposed and demonstrated on the basis of a polarization-diversified loop comprised of a four-port polarization beam splitter, four rotatable half-wave plates (HWPs), and three high birefringence fiber (HBF) segments. Each HBF segment is positioned between two adjoining HWPs, and two HWPs located among the three HBF segments determine the effective angular orientation difference among their principal axes, or fast and slow axes. At specific orientation angles of the four HWPs, second-order comb spectra such as flat-top and narrow-band ones could be obtained with a free spectral range (FSR) of ∼0.792  nm. In particular, the frequency interleaving of these second-order comb spectra, that is, a half FSR switching, could be implemented by controlling two out of four HWPs, which is the first demonstration of the interleaving operation in second-order comb spectra without expensive birefringence modulators. These spectral characteristics of the proposed filter were theoretically predicted and experimentally demonstrated.

We analyze the method to uniform the output signal power spectrum for a long-haul wavelength-division-multiplexing (WDM) system using backward multipump Raman amplifiers with arbitrary initial input signal power spectrum. A genetic algorithm is used to optimize the output signal power. The theoretical results show that using variable pump wavelengths is better than using fixed pump wavelengths to decrease the spectral maximum power difference. An experiment is conducted based on the theoretical analysis. The results agree well with the numerical calculations.

An orthogonal frequency division multiplexing (OFDM) technique called flipped OFDM (flip-OFDM) is apposite for a visible light communication system that needs the transmitted signal to be real and positive. Flip-OFDM uses two consecutive OFDM subframes to transmit the positive and negative parts of the signal. However, peak-to-average power ratio (PAPR) for flip-OFDM is increased tremendously due to the low value of total average power that arises from many zero values in both the positive and flipped frames. We first analyze the performance of flip-OFDM and perform a comparison with the conventional DC-biased OFDM (DCO-OFDM); then we propose a flip-OFDM scheme combined with μ-law mapping to reduce the high PAPR. The simulation results show that the PAPR of the system is reduced about 17.2 and 5.9 dB when compared with the normal flip-OFDM and DCO-OFDM signals, respectively.

A theoretical analysis was conducted on the characteristics and performance of an optically combined dual-loop optoelectronic oscillator (OC-DOEO) based on an open-loop response method. The OC-DOEO utilizes the Vernier effect to eliminate spurious tones while accompanying the optical interference among the dual-loop signals. It was determined that the optical interference in the OC-DOEO significantly affected the OEO performances, including loop efficiency, phase noise, and spurious tones. It was demonstrated that DOEO performances can be maximized by controlling dual-loop parameters, such as the phase delay and power-split ratio, without spurious tones.

We constructed a temperature-controlled Fourier domain mode locking (TC-FDML) laser capable of high-speed wavelength sweeping and developed a real-time fiber Bragg grating (FBG) measurement system. The TC-FDML laser can perform high-speed wavelength sweeping at a sweep frequency of 50.7 kHz with a scan range of ∼60  nm in the 1.55-μm band. This system uses a data acquisition system mounting an analog/digital converter and field programmable gate array that enables real-time FBG measurement at a sampling frequency of 250 MHz. Using bidirectional wavelength sweeping by the TC-FDML laser, the system has a measurement time resolution of 9.9  μs. We show that the developed system can measure high-speed vibrations of several kHz and perform simultaneous and continuous measurements of multiple FBGs for a period of one hour.

An open-path atmospheric CO2 measurement system was built based on tunable diode laser absorption spectroscopy (TDLAS). The CO2 absorption line near 2  μm was selected, measuring the atmospheric CO2 with direct absorption spectroscopy and carrying on the comparative experiment with multipoint measuring instruments of the open-path. The detection limit of the TDLAS system is 1.94×10−6. The calibration experiment of three AZ-7752 handheld CO2 measuring instruments was carried out with the Los Gatos Research gas analyzer. The consistency of the results was good, and the handheld instrument could be used in the TDLAS system after numerical calibration. With the contrast of three AZ-7752 and their averages, the correlation coefficients are 0.8828, 0.9004, 0.9079, and 0.9393 respectively, which shows that the open-path TDLAS has the best correlation with the average of three AZ-7752 and measures the concentration of atmospheric CO2 accurately. Multipoint measurement provides a convenient comparative method for open-path TDLAS.

A quadruple micro-optical ring resonator (QMORR) with multiple output bus waveguides is mathematically modeled and analyzed by making use of the delay-line signal processing approach in Z-domain and Mason’s gain formula. The performances of QMORR with two output bus waveguides with vertical coupling are analyzed. This proposed structure is capable of providing wider free spectral response from both the output buses with appreciable cross talk. Thus, this configuration could provide increased capacity to insert a large number of communication channels. The simulated frequency response characteristic and its dispersion and group delay characteristics are graphically presented using the MATLAB environment.

A tunable ultraflat optical frequency comb generator based on the optoelectronic oscillator (OEO) using a dual-parallel Mach–Zehnder modulator (DPMZM) is proposed and experimentally demonstrated. By incorporating a tunable DPMZM-OEO, five comb lines were generated with frequency spacing from 5 to 12 GHz under a wide central wavelength tuning from 1530 to 1560 nm, and a comb flatness of 0.3 dB is obtained. The corresponding signal generated by the DPMZM-OEO is also measured, and the phase noise of the frequency tunable signals is as low as −125  dBc/Hz at 10-kHz frequency offset.

An enhanced minimum mean-square-error (MMSE) frequency-domain (FD) fractionally spaced equalizer (FSE) for polarization demultiplexing is proposed in the presence of colored noise. The 2-norm of the estimated channel matrix and polynomial fitting of equalization coefficients are introduced to mitigate the colored noise without requiring knowledge of the optical and electrical filtering. Simulation results show that ∼3-dB improvement of equalization performance is achieved compared to conventional MMSE FD-FSE in an 8×112-Gbit/s wavelength-division multiplexing polarization-division multiplexing-quadrature phase shift keying transmission system over a 1200-km single mode fiber link.

The use of integrated waveguide modulators is a common technique in electric-field sensing. However, the distortion in the modulated signal caused by high half-voltage Vπ and the difficulty in obtaining low-frequency responses are challenging issues for the use of low-frequency alternating-current (AC) electric-field sensors. This study investigates the use of an optimized segmented slot waveguide as the core of a sensor to determine the sensor features that produce useful frequency responses and sensitivity. The segmented slot waveguide is optimized in terms of periodicity and segment width to produce low Vπ and electrical bandwidth before testing the sensor sensitivity. The results show that reducing the segment width achieves a low Vπ of 0.32 V and a very low electrical bandwidth of 4.3 kHz. Our study provides evidence of the feasibility of using a segmented slot waveguide as the primary element for highly sensitive, low-frequency AC electric-field sensors.

A parallel graphene layer pair arranged in an antisymmetric configuration coupled through a cavity resonator is proposed and analyzed by the analytical method and the numerical finite-difference time-domain method. The structure operates as a bandpass filter in the midinfrared region. The feature, as the result of the wavelength selective property of the cavity resonator, can be tuned by varying the length of the resonator, the lateral coupling distance between the graphene layers, the dielectric refractive index of material inside the resonator, and, the most interesting, the chemical potential of the graphene layers. The proposed structure can be promoted to power splitters and refractive index sensors by proper designs. Various power division ratios can be realized by changing the relative positions and/or the chemical potentials of the output waveguides. The investigated components can be utilized in the design of midinfrared nanoscale photonic integrated circuits.

The issue of thermal effects is inevitable for the ultrahigh refractive index (RI) measurement. A biosensor with parallel-coupled dual-microring resonator configuration is proposed to achieve high resolution and free thermal effects measurement. Based on the coupled-resonator-induced transparency effect, the design and principle of the biosensor are introduced in detail, and the performance of the sensor is deduced by simulations. Compared to the biosensor based on a single-ring configuration, the designed biosensor has a 10-fold increased Q value according to the simulation results, thus the sensor is expected to achieve a particularly high resolution. In addition, the output signal of the mathematical model of the proposed sensor can eliminate the thermal influence by adopting an algorithm. This work is expected to have great application potentials in the areas of high-resolution RI measurement, such as biomedical discoveries, virus screening, and drinking water safety.

The theory of biexciton (formed from spatially separated electrons and holes) in a nanosystem consisting of double quantum dots (QDs) of germanium synthesized in a silicon matrix is presented. It is shown that the major contribution to the biexciton binding energy is made by the energy of the exchange interaction of electrons with holes and this contribution is much more substantial than the contribution of the energy of Coulomb interaction between the electrons and holes. The position of the biexciton state energy band depends both on the mean radius of the QDs and the distance between their surfaces, which enables one to purposefully control it by varying these parameters of the nanostructure.

The Verdet constant dispersion of CeF3 crystal was measured in the spectral range from 0.45 to 1.95  μm. To the best of our knowledge, CeF3 crystal was investigated for the first time as a potential material candidate for near-infrared Faraday rotators (FRs). The experimental results obtained for Verdet constant dispersion were compared to other magneto-optical materials with the conclusion that CeF3 crystal possesses up to 60% higher Verdet constant in the near-infrared spectral region 1.1 to 1.5  μm compared to widely used terbium gallium garnet crystal. Furthermore, the presented experimental setup is capable of high precision measurement of Verdet constant dispersion in a broad spectral range, with measurement error not exceeding 5%, therefore, representing a powerful tool for FRs development.

Based on a long-period fiber grating, we conducted experimental research on the temperature sensitivity of topological insulators. The long-period fiber grating and topological insulators solution were encapsulated in a capillary tube using UV glue, and the temperature response was measured. Within a range of 35 to 75 centigrade, one resonance dip of a long-period fiber grating exhibits a redshift of 1.536 nm. The temperature sensitivity is about 7.7 times of an ordinary long-period fiber grating’s sensitivity (0.005  nm/°C). A numerical simulation is also performed on the basis of the experiments.

Highly ordered anodic aluminum oxide (AAO) membranes are fabricated electrochemically in an electrolyte mixture with various concentrations of C2H2O4 or NH4F. Photoluminescence (PL) properties of AAO membranes have been investigated before and after annealing in the range from 300°C to 650°C. X-ray diffraction reveals the amorphous nature of AAO membranes. Energy dispersive spectroscopy indicates the presence of fluorine species incorporated in oxide membranes during the anodizing. PL measurements show a strong PL band in the wavelength range of 350 to 550 nm. With the increase of the concentration of the NH4F or C2H2O4 in the electrolyte mixture, the peak positions of the PL bands have a blueshift or redshift and the intensities have a maximum value. As indicated by the PL excitation spectra, there are two excitation peaks of 285 and 330 nm, which can account for the PL emission band. We have proposed that the PL originates from optical transitions in two kinds of centers that are related to oxygen vacancies, F+ (285 nm) and F (330 nm). This work is not only beneficial to further understanding of the light-emitting property of AAO membranes but also enlarges the application scope.

A double-cavity graphene photodetector consisting of filtering cavity and absorption cavity with high performance is proposed. The device has an ultranarrow response linewidth and high quantum efficiency as well as high response speed. By taking full advantage of the double cavity, the structure parameters of the photodetector are deeply optimized, and 88% peak quantum efficiency with 0.75-nm linewidth is obtained. It is believed that the double-cavity graphene photodetector has promising and potential application in a high-speed density wavelength-division multiplexing system.

An ultracompact double eight-shaped plasmonic structure for the realization of plasmon-induced transparency (PIT) in the terahertz (THz) region has been studied. The device consists of a semiconductor–insulator–semiconductor bus waveguide coupled to the dual-disk resonators. Indium antimonide is employed to excite SPP in the THz region. The transmission characteristics of the proposed device are simulated numerically by the finite-difference time-domain method. In addition, a theoretical analysis based on the coupled-mode theory for transmission features is presented and compared with the numerical results. Results are in good agreement. Also, the dependence of PIT frequency characteristics on the radius of the outer disk is discussed in detail. In addition, by removing one of the outer disk resonators, double-PIT peaks can be observed in the transmission spectrum, and the physical mechanism of the appeared peaks is investigated. Finally, an application of the proposed structure for distinguishing different states of DNA molecules is discussed. Results show that the maximum sensitivity with 654  GHz/RIU−1 could be obtained for a single PIT structure. The frequency shifts equal to 37 and 99 GHz could be observed for the denatured and the hybridized DNA states, respectively.

Composite thin films formed by nanometer-sized metal particles embedded in dielectric matrices were fabricated by codepositing the metal and ceramic targets using a pulsed laser deposition technique. The optical absorption properties were measured from 350 to 800 nm, and the absorption peak due to the surface plasmon resonance of metal particles was found. The effects of different metal particles (Au, Ag, Fe, and Co) and embedding matrices (SrTiO3, Al2O3, and TiO2) on the optical absorption properties of the composite films were discussed. Strong absorption peaks can be found in composite films doped with noble metal particles, while most transition metal particles show ordinary absorption patterns. Dielectric properties of metal particles and the refractive index of embedding matrices were responsible for the observed results.

The SrS : Eu 0.02 2 + , Dy 0.01 3 + phosphors modified with stearic acid (SA) were compounded with the polyvinyl butyral (PVB) matrix to improve its chemical stability and luminescence properties. The structure and luminescence properties of modified and unmodified SrS : Eu 0.02 2 + , Dy 0.01 3 + and SrS : Eu 0.02 2 + , Dy 0.01 3 + / PVB composites were studied. The results of x-ray diffraction showed that the crystalline of the modified SrS : Eu 0.02 2 + , Dy

We present thermal tuning of air-suspended SU-8 polymer waveguide grating couplers for TE-polarized light. Numerical simulations have been performed to estimate the wavelength shift caused by the change of temperature. Due to the small positive thermal expansion and large negative thermo-optic coefficient of SU-8, a shift toward shorter wavelengths is expected. In the experimental evaluation, a negative wavelength shift from 1542 nm at 20°C toward 1527 nm at 56°C is obtained with approximately −0.42  nm K−1 matching the theoretical considerations.

An epsilon-near-zero graphene–silica metamaterial-based structure is proposed and numerically investigated to realize super-reflection and cloaking. The advantage of this structure is that the operating bandwidth can be actively controlled by varying the chemical potential of graphene. By applying different electromagnetic boundary conditions, super-reflection and cloaking can be realized no matter what shape and size the object is inside this device. The ultracompact structure has potential applications in microcosmic science and military detection.