Integrated optics is the field where photonics and glass science smartly cooperate to develop new physics, new devices, and new applications. Glass materials and photonic structures are the cornerstones of scientific and technological building in integrated optics. Photonic glasses, optical glass waveguides, planar light integrated circuits, waveguide gratings and arrays, functionalized waveguides, photonic crystal heterostructures, and hybrid microresonators are some examples of glass-based integrated optical devices that play a significant role in optical communication, sensing, biophotonics, processing, and computing.

We consider the design methods and operation principles of a fast-response optical sensor for precise measurement of small temperature variations, which is based on ring resonators of micron size made from waveguides with one or two slots filled by a liquid crystal. The sensor sensitivity and measurement region can be changed by modifying the parameters of the waveguide or resonator, such as width of the waveguide strips or slots, slot separation, resonator bend radius, coefficient of coupling between the ring and input/output waveguides, etc. We analyzed the dependence of the transverse field distribution and effective indices of the orthogonally polarized modes in the slot and double-slot waveguides on the waveguide and resonator parameters, and we have considered the optimization of the temperature sensor structure based on such waveguides.

We present the design, simulation, evaluation, and technological verification of various low-index optical demultiplexers based on arrayed waveguide gratings (AWGs). When designing such optical demultiplexers, a set of input geometrical parameters must be first calculated. They are essential to create AWG layout that will be then simulated using commercial photonics tools. However, these tools do not support or support only partially such a fundamental calculation. Therefore, a new stand-alone tool called AWG-Parameters was developed, which strongly reduces the time needed for the design. From the calculated geometrical parameters, the AWG layouts were created and simulated using three commercial photonic tools: Optiwave, (Ottawa, Ontario, Canada), Apollo Photonics, (Ancaster, Ontario, Canada), and R-Soft, (Pasadena, California). The designs were also technologically verified. The simulated/measured transmission characteristics were evaluated by our newly developed AWG-Analyzer tool. This tool provides calculations of AWG transmission parameters, which are also missing in commercial photonic tools. Additionally, the tool provides clear definitions of calculated transmission parameters together with their textual and graphical representations. Finally, the transmission characteristics and parameters achieved from different photonic tools were compared with each other and discussed in detail. The simulated results were also compared with the measurements. Very good agreement was achieved between theoretical (AWG-Parameters tool), simulated (commercial photonic tools), and fabricated AWG transmission parameters.

Some of the main results obtained in the field of glass-based photonic crystal (PC) systems using complementary techniques, such as radio frequency (RF) sputtering and sol-gel route, are presented. Initially, rare earth-activated one-dimensional PCs fabricated by RF-sputtering technique will be discussed, specifically the cavity is constituted by an Er³+ -doped SiO₂active layer inserted between two Bragg reflectors consisting of 10 pairs of SiO₂/TiO2/layers. Moreover, from near infrared, transmittance and variable angle reflectance spectra have verified the presence of a stop band from 1500 to 2000 nm with a cavity resonance centered at 1749 nm at 0 deg and quality factor of 890. In the second case, a composite system based on polystyrene colloidal nanoparticles assembled and embedded in an elastomeric matrix will be presented in detail. This system has been designed as a structure that displays an iridescent green color that can be attributed to the PC effect. This feature has been exploited to create a chemical sensor; in fact optical measurements have evidenced that this system presents a different optical response as a function of the solvent applied on the surface, showing: (1) high sensitivity, (2) fast response, and (3) reversibility of the signal change.

A mid-IR amplifier consisting of a tapered chalcogenide fiber coupled to an Er3+-doped chalcogenide microsphere has been optimized via a particle swarm optimization (PSO) approach. More precisely, a dedicated three-dimensional numerical model, based on the coupled mode theory and solving the rate equations, has been integrated with the PSO procedure. The rate equations have included the main transitions among the erbium energy levels, the amplified spontaneous emission, and the most important secondary transitions pertaining to the ion-ion interactions. The PSO has allowed the optimal choice of the microsphere and fiber radius, taper angle, and fiber-microsphere gap in order to maximize the amplifier gain. The taper angle and the fiber-microsphere gap have been optimized to efficiently inject into the microsphere both the pump and the signal beams and to improve their spatial overlapping with the rare-earth-doped region. The employment of the PSO approach shows different attractive features, especially when many parameters have to be optimized. The numerical results demonstrate the effectiveness of the proposed approach for the design of amplifying systems. The PSO-based optimization approach has allowed the design of a microsphere-based amplifying system more efficient than a similar device designed by using a deterministic optimization method. In fact, the amplifier designed via the PSO exhibits a simulated gain G=33.7  dB , which is higher than the gain G=6.9  dB of the amplifier designed via the deterministic method.

The light Bloch oscillations in the array of optical waveguides are investigated based on the electrodynamics of continual approach. The array possesses a step-like refractive index profile. Usually, these oscillations are described in a phenomenological manner. However, the parameters entering the phenomenological equations are obtained either from additional numerical simulations or from experiments. The approach proposed here is based on multiple-scattering formalism. This approach allows us to justify the phenomenological description. The phenomenological approach is valid only if the interaction between the waveguides is weak and the nearest neighbor approximation is applicable. To describe the path of light, we calculate the local isofrequency curve. It is shown that the path represents Bloch oscillations. The results obtained are found to correlate with the experiments available.

Antimony-germanate glasses co-doped with Er ³+ /Tm ³+ ions as a material for active waveguides application have been investigated. In result of optimizations of rare earths, concentration wide (Δλ FWHM =420  nm ) luminescence emission in the range of 1.4 to 1.9 μm was obtained for molar composition of 1%Er ₂ O ₃ : 0.25%Tm ₂ O ₃ . The influence of the molar ratio of active ions on the luminescence spectra has been investigated. Luminescent properties of fabricated glass indicate that elaborated glass is promising material for broad tunable integrated laser sources and broadband optical amplifiers.

The optical properties of photonic devices largely depend on the dielectric properties of the underlying materials. We apply modern ab initio methods to study crystalline SiO₂ phases, which serve as toy models for amorphous glass. We discuss the dielectric response from the infrared to the VIS/UV, which is crucial for glass based photonic applications. Low density silica, like cristobalite, may provide a good basis for high transmission optical devices.

This work describes a computational approach for the optical characterization of an opal photonic crystal (PC). We intend, in particular, to validate our approach by comparing the transmittance of a crystal model, as obtained by numerical simulation, with the transmittance of the same crystal, as measured over 400- to 700-nm wavelength range. We consider an opal PC with a face-centered cubic lattice structure of spherical particles made of polystyrene (a nonabsorptive material with constant relative dielectric permittivity). Light-crystal interaction is simulated by numerically solving Maxwell’s equations via the finite-difference time-domain method and by using the Kirchhoff formula to calculate the far field. A method to study the propagating Bloch modes inside the crystal bulk is also sketched.

We present an analytical model for a generic two-wave directional coupler, in the conceptual frame of coupled single-mode planar (slab) waveguides. The modal relation of dispersion is expressed exactly under a matrix form. In the simplest symmetric configuration, the lift of degeneracy between the propagation constants of the even (slow) and odd (fast) supermodes is the exact image of the coupling constant.

We demonstrate a way of light harvesting in integrated microfluidic chips fabricated by femtosecond laser micromachining. The architecture consists of waveguide arrays fabricated in the vicinity of the microchannel filled with a fluorescent organic solution (e.g., polyfluorene solution). Amplified spontaneous emission from the microchannel is efficiently coupled by the waveguides to the outside of the chip.

Large third-order nonlinearity and transparency in the mid-infrared region are the basic motivations for prospective applications of chalcogenide glasses in nonlinear photonics and laser technologies. We present the state-of-the-art and our recent results of measurement and evaluation of the nonlinear optical constants, plasma dynamics, and thermal regimes upon irradiation of As-S-Se samples using 40-fs pulses at 790-nm wavelength.

We report the fabrication of micro-Fresnel lenses by femtosecond laser surface ablation on one-dimensional (1-D) polymer photonic crystals. This device is designed to focus the transmitted wavelength (520 nm) of the photonic crystal and filter the wavelengths corresponding to the photonic band-gap region (centered at 630 nm, ranging from 530 to 700 nm). Integration of such devices in a wavelength selective light harvesting and filtering microchip is envisaged.

The paper presents the visible emissions through frequency up-conversion and energy transfer process in the waveguide rare-earth (RE) codoped with RE ³+ /Yb ³+ (RE=Er , Pr, Tm), as well as physical properties of fluoride glasses and their fabrication par physical vapor deposition. The RE doping is made by substituting LaF ₃ in the base ZLAG glass composition (70%ZrF ₄ -23.5%LaF ₃ -0.5%AlF ₃ -6%GaF ₃ ). Under 980-nm excitation, the emissions in planar waveguides of 2 to 3 thickness are found similar to the ones observed in bulk; blue and red emissions for 0.5Pr ³+ /xYb ³+ codoping and blue emission for 0.75Tm ³+ /xYb ³+ codoping with x ranging from 1 to 5 mol%. The bulk glass doped with Er ³+ /Tm ³⁺ /Yb ³+ can generate simultaneously and with high efficiency red–green–blue emissions from single-wave pumping at 980 nm. These preliminary results show that Er ³+ /Tm ³+ /Yb ³+ triply doped ZLA waveguide is a potential material for compact white light sources.

Thermally stable tellurite, lead-bismuth-gallium oxides based boron-silicate and lead-silicate glasses dedicated for multiple thermal processing are presented. The glasses are successfully used for the development of photonic crystal fibers, nanostructured gradient index lenses, all-solid microstructured fibers as well as refractive or diffractive micro-optical elements with ultra-broadband transmission.

We developed Hg ²+ -sensing chips by decorating the external surface of metal-clad optical waveguides with a monolayer of Hg ²+ -sensitive fluorescent molecular probes. The emission properties of the original water-soluble form of the molecule were previously found to be selectively quenched in the presence of Hg ²+ ions. The fabricated samples were tested with optical waveguide fluorescence spectroscopy by putting them in contact with a 5-μM water solution of Hg ²+ ions and recording the emission spectra versus incubation time. The estimate of the limit of detection was 150 nM. A preliminary evaluation of the selectivity of the structure was also performed by using Cd ²+ as possible interfering analytes.

We propose an in-depth investigation of all-solid microstructured optical fibers for the development of very large mode area (VLMA) fiber lasers. The inner cladding microstructure of these VLMA fibers is carefully optimized in order to get a robust single-mode laser operation in the high power regime. We describe the numerical approach used to devise a novel kind of fiber structures, the core of which should be larger than 50 μm while showing an improved single-mode emission compared to that of the state-of-the-art large pitch fibers. With the aim of overpassing the limitations of chemical vapor deposition techniques, we opted for a manufacturing process called Repusil, based on the sintering and vitrification of doped powders. Then, our opto-geometrical considerations result from the optical properties offered by this method and the use of the stack and draw. Finally, we present our very first fabrication for the proposed all-solid microstructured fibers in which a laser emission of 52 W in a continuous wave regime was obtained.

Glass and polymer interstacked superlattice like nanolayers were fabricated by nanosecond-pulsed laser deposition with a 193-nm-ultraviolet laser. The individual layer thickness of this highly transparent thin film could be scaled down to 2 nm, proving a near atomic scale deposition of complex multilayered optical and electronic materials. The layers were selectively doped with Er ³+ and Eu 3₊ ions, making it optically active and targeted for integrated sensor application.

Glasses, either pure or suitably doped, constitute an excellent material for the development of integrated optical circuits. A brief review is presented of the most widely used processes for the fabrication of passive and active glass waveguides. Brilliant prospects of glass-based platforms for the development of photonic integrated circuits are outlined.

We report on the growth, spectroscopy, and laser emission of two fluoride materials, LiLuF ₄ and KY ₃ F ₁₀ , doped with Ho ³+ . In particular, laser emission has been obtained for the first time from a Ho ³+ :KY ₃ F ₁₀ crystal, grown with the Czochralski technique. Utilizing the micropulling down (μ-PD) method, we grew a Ho ³+ :LiLuF 4 crystal, which allowed us to obtain an efficient laser emission in the 2-μm spectral region. The KY ₃ F ₁₀ has a cubic symmetry and it is particularly suitable for technological applications, while the μ-PD technique is appealing for high-power applications. We present the spectroscopic characterization of the two crystals as a function of temperature in the range 10 to 300 K and few laser results.

Crystalline whispering-gallery-mode disk resonators are finding an increasing number of applications in photonics. Their exceptional energy storage capacity is of great interest in the area of ultrastable oscillators for aerospace and communication engineerings as well as for sensing applications. Here, we investigate the physical properties of some unconventional crystalline materials. We show that these resonators can display quality factors higher than ten million at 1550 nm and we discuss their potential for various applications.

Structural and optical properties of the porous anodic alumina (PAA)–aluminum (Al) nanocomposite and the PAA-nanostructured films on borofloat substrates are studied. The films are fabricated by the anodization of 170- to 200- and 295- to 330-nm-thick Al sputtered onto the borofloat. The anodization process is stopped at different times in order to form the PAA–Al nanocomposite films with different layer thicknesses. Then, the pore widening is applied to 189- to 210- and 430- to 495-nm-thick PAA films in 5- and 10-min intervals, respectively. The structural properties of the films are characterized by a scanning electron microscopy. The nanocomposite films are also characterized optically by total reflection and directional transmission measurements in the wavelength range between 250 and 800 nm. Our results indicate that controlling the thicknesses of both Al and the PAA layers by anodization time and the morphology of the nanostructures by chemical etching duration in the PAA layer provides unique PAA–Al nanocomposite films with desired optical properties.

Silver nanostructures were fabricated by laser direct writing technique using 796-nm Ti:Sapphire femtosecond laser pulses in polymer matrix containing silver ions that has been spin coated on a silicon substrate. Silver nanostructures that resulted inside the polymer matrix were obtained by the nonlinear optical interaction between femtosecond laser pulses and polymer films containing silver ions. We report here the characterization of the silver nanostructures using UV-Vis extinction spectra, field emission scanning electron, and atomic force microscope images. Formation of silver nanoparticles inside the laser written microstructures is confirmed by the appearance of surface plasmon absorption band at 448 nm in the UV-Vis extinction spectrum. Nanoparticles formed were spherical in shape with average particle size <20  nm . This technique is a cost-effective approach and has potential applications in the fabrication of fine metallic micro/nanostructures for microelectromechanical systems, nanoelectronics, and nanophotonics.

The versatility of hot embossing for shaping photonic components on-chip for mid-infrared (IR) integrated optics, using a hard mold, is demonstrated. Hot embossing via fiber-on-glass (FOG), thermally evaporated films, and radio frequency (RF)-sputtered films on glass are described. Mixed approaches of combined plasma etching and hot embossing increase the versatility still further for engineering optical circuits on a single platform. Application of these methodologies for fabricating molecular-sensing devices on-chip is discussed with a view to biomedical sensing. Future prospects for using photonic integration for the new field of mid-IR molecular sensing are appraised. Also, common methods of measuring waveguide optical loss are critically compared, regarding their susceptibility to artifacts which tend artificially to depress, or enhance, the waveguide optical loss.

A just noticeable disparity error (JNDE) measurement to describe the maximum tolerated error of depth maps is proposed. Any error of depth value inside the JNDE range would not cause a noticeable distortion observed by human eyes. The JNDE values are used to preprocess the original depth map in the prediction process during the depth coding and to adjust the prediction residues for further improvement of the coding quality. The proposed scheme can be incorporated in any standardized video coding algorithm based on prediction and transform. The experimental results show that the proposed method can achieve a 34% bit rate saving for depth video coding. Moreover, the perceptual quality of the synthesized view is also improved by the proposed method.

A dual Cauchy rate-distortion model is proposed for video coding. In our approach, the coefficient distribution of the integer transform is first studied. Then, based on the observation that the rate-distortion model of the luminance and that of the chrominance can be well expressed by separate Cauchy functions, a dual Cauchy rate-distortion model is presented. Furthermore, the simplified rate-distortion formulas are deduced to reduce the computational complexity of the proposed model without losing the accuracy. Experimental results have shown that the proposed model is better able to approximate the actual rate-distortion curve for various sequences with different motion activities.

Reversible integer time-domain lapped transform (RTDLT) has been proven to be efficient in progressive lossy-to-lossless image compression. We introduced the quadtree-based RTDLT (QRTDLT) to further improve the performance of block-transform methods.Traditional block transforms are usually conducted with a fixed size of 8×8 or 16×16. This is an oversimplified and hardware-friendly implementation, but it is not optimal for different areas of various images. In the proposed QRTDLT method, we first partitioned the image into macroblocks. Then, the macroblocks are iteratively processed using quadtree splitting while abiding by special regulation. These blocks are transformed by RTDLTs with different-length basis functions. With limited complexity increase, the QRTDLT is still suitable for online applications of image compression. Simulation results demonstrated that the proposed method yields more than 0.5-dB performance improvement in lossy compression. At the same time, the QRTDLT also performs better than the RTDLT in lossless compression.

Time-of-flight (TOF) range sensors acquire distances by means of an optical signal delay measurement. As the signal travels at the speed of light, distance resolutions in the subcentimeters range require a time measurement resolution that is in the picoseconds range. However, typical clock synthesizers and digital buffers possess cycle-to-cycle jitter values of up to hundreds of picoseconds, which can potentially have a noticeable impact on the TOF system performances. In this publication, we investigate the influence of two common types of cycle-to-cycle jitter distributions on the measured distance. This includes a random Gaussian distribution, which is caused by, e.g., stochastic noise sources, and a discrete jitter distribution, which is found when timing constraints fail in synchronous digital designs. It was demonstrated that a Gaussian cycle-to-cycle jitter has only a negligible impact on the performance of the TOF distance sensors up to a standard deviation of 1 ns of the Gaussian jitter distribution. However, even the discrete cycle-to-cycle jitter investigated in its simplest form lowers the distance precision of the TOF sensor by a factor of 2.86, i.e., the standard deviation increases from 2.9 to 8.3 mm.

Optical coherence tomography (OCT) is a high-resolution noninvasive technology used in medical imaging for the spatial visualization of biological tissue. Due to its coherent nature, OCT suffers from speckle noise, which significantly degrades the information content of resulting scans. We introduce a new filtering method for three-dimensional OCT images, inspired by film grain removal techniques. By matching structural relatedness along all dimensions, the algorithm builds up vector paths for every voxel in the image volume representing its structural neighborhood. Then, by considering the information redundancy along these paths, our filter is able to reduce speckle noise significantly while simultaneously preserving structural information. This filter exceeds some common three-dimensional denoising algorithms used for OCT images, both in visual rendering quality and in measurable noise reduction. The noise-reduced results allow for improvement in subsequent processing steps, such as image segmentation.

Low-coherence interferometric setups in the Fourier domain can experience false structures after the Fourier transform procedure due to signal saturation; in fact, these structures are located at multiple frequencies of the original signal, also referred to as harmonics. This study aids in a better understanding of this phenomenon. The aim of the present work was to show that these features can be used to improve differential axial resolution in highly reflective samples. Using an optical coherence tomography system and calibrated step height standards, it was possible to achieve a resolution greater than the light source coherence length.

An automatic geometrical calibration approach has been developed to calibrate a multiprojector-type light field (LF) display automatically and accurately. The calibration framework based on image mapping is detailed, which transfers the calibration of three-dimensional (3-D) scene into the calibration of two-dimensional image in the diffuser interface. A multiprojectors-type LF display prototype is applied to implement the experimental calibration. Comparison results of the reconstructed 3-D scene before and after calibration show that a better overall performance is obtained through the proposed calibration approach.

We propose a texture saliency classifier to detect people in a video frame by identifying salient texture regions. The image is classified into foreground and background in real time. No temporal image information is used during the classification. The system is used for the task of detecting people entering a sterile zone, which is a common scenario for visual surveillance. Testing is performed on the Imagery Library for Intelligent Detection Systems sterile zone benchmark dataset of the United Kingdom’s Home Office. The basic classifier is extended by fusing its output with simple motion information, which significantly outperforms standard motion tracking. A lower detection time can be achieved by combining texture classification with Kalman filtering. The fusion approach running at 10 fps gives the highest result of F1=0.92 for the 24-h test dataset. The paper concludes with a detailed analysis of the computation time required for the different parts of the algorithm.

Pickup method adopting the modified algorithm to generate the elemental image from virtual objects is proposed to obtain the elemental image for real objects. In the proposed method, the number of capturing processes is reduced compared with the conventional multiple capturing method. The pseudoscopic image problem can be resolved by controlling the position and the direction of the imaging device in the proposed pickup system. The telecentric lens system is used to capture the orthographic scenes, which are divided and compounded into the elemental image. The validity of the proposal is proved by the experimental results of the pickup and the reconstruction.

Temperature measurement by infrared thermography is a technique that is widely used in predictive maintenance to detect faults. The uncertainty involved in measuring temperature by thermography is not only due to the imager, but also due to the measurements and estimates made by the user: emissivity of the inspected object, distance, temperature, and relative humidity of the propagation medium, temperature of objects located in the ambient, and the imager itself. This measurement uncertainty should be available for the thermographer to be able to make a more accurate diagnosis. The methods available in the literature to estimate the uncertainty of measured temperature usually require information nonaccessible to the regular thermographer. This paper proposes a method for calculating the uncertainty of temperature that requires only data available to the thermographer. This method is useful under usual conditions in predictive maintenance—short distance (7.5 to 14 μm) thermal imagers, no fog or rain, among others. It provides results similar to methods that use models that are not available or reserved by the manufacturers of imagers. The results indicate that not all sources of uncertainty are relevant in measurement uncertainty. However, the total uncertainty can be so high that it may lead to misdiagnosis.

Terahertz (THz) time-domain spectroscopy is considered as an attractive tool for the analysis of chemical composition. The traditional methods for identification and quantitative analysis of chemical compounds by THz spectroscopy are all based on full-spectrum data. However, intrinsic features of the THz spectrum only lie in absorption peaks due to existence of disturbances, such as unexpected components, scattering effects, and barrier materials. We propose a strategy that utilizes Lorentzian parameters of THz absorption peaks, extracted by a multiscale linear fitting method, for both identification of pure chemicals and quantitative analysis of mixtures. The multiscale linear fitting method can automatically remove background content and accurately determine Lorentzian parameters of the absorption peaks. The high recognition rate for 16 pure chemical compounds and the accurate predicted concentrations for theophylline-lactose mixtures demonstrate the practicability of our approach.

We proposed and experimentally demonstrated a delay-match sampling method to measure and compensate the laser phase error in optical frequency-domain reflectometry system. By using the error signal extracted from a simple auxiliary Mach-Zehnder interferometer with only a 10-ns delay, the laser phase error is effectively compensated. Considerable improvement is achieved in spatial resolution from 200 m to 7 cm at a measurement distance over 10 times the round-trip laser coherence length.

A simple and effective automatic positioning method (APM) is proposed for the application of annular subaperture stitching interferometry in the stage of precision polishing. In the testing process, a series of optical path difference (OPD) data of subaperture are obtained since the interferometer is shifted relative to the tested aspheric surface. These OPD data are analyzed by the APM to get the key stitching parameters (e.g., aspheric departure) without a precision motion system. The basic principles of the APM are described. The performance of the method is simulated in some pertinent cases. Finally, we study the applicability of the proposed method to subaperture stitching tests of a hyperbolic mirror. The stitching results agree with the full-aperture test results. It demonstrates the validity and practicability of the proposed algorithm.

Thermal barrier coatings (TBCs) and plasma spray coatings, in general, require fine control over the deposited thickness to achieve a reliable coating performance. Currently, the plasma spray industry quantifies thickness by sampling the part before and after TBC deposition. Approximate thickness is inferred from previous runs; however, process variability can cause errors in these approximations that result in wasted time and resources that can ultimately lead to nonreliant coatings. To this end, we present an in situ optical fringe projector technology that enables coating thickness measurements across a two-dimensional surface. The sensor is capable of achieving micron scale resolution in the harsh environment of a thermal spray booth. Furthermore, unlike the existing approaches, this technique is extendable to parts with complex geometries. The underlying background of the fringe projection method, including a differential measurement technique, is presented. Current results on production equipment and cylindrical parts are also discussed, showing good correlation and agreement with physical measurements captured in an industrial setting.

A noninterferometric technique used to measure the diffusion coefficients of transparent liquid solutions is reported. This technique uses a white light source and a diffusion cell, with an artificially developed fringe pattern of dark and white stripes at its entrance. As the diffusion process takes place in the cell, the light passing through this nonuniform refractive index medium will bend toward the higher refractive index region, which results in a fringe shift. This shift in the fringe pattern at different times is recorded in a personal computer (PC) using a CCD camera for the calculation of diffusion coefficients. The fringe shift is calculated after skeletonization and linear fit of the captured fringe system. The diffusion coefficient of different concentrations of ammonium dihydrogen phosphate was determined using the proposed technique and the measured values lay within 1% of the reported values. Detailed theoretical and experimental analyses with a comparison of other existing results are discussed.

A method using rotating Fabry–Perot (FP) mirror to measure CO₂ laser wavelength was developed. The variation of FP transmittance changing with laser incident angle was calculated theoretically and the variation curve was given. The calculation illustrates that the variation of FP reflectance with incident angle 0 to 30 deg has little effect on the transmittance of FP. In the experiments, the CO₂ laser transmittance variation of FP was measured at a wavelength of 9.27 μm. To improve the measurement precision of the laser wavelength, the method using the centrosymmetric peaks of FP transmittance curve in the range from −20 to +20  deg of laser incident angle was proposed. The precision of the measurement is about 0.01 μm. The experiment result is consistent with theoretical analysis, which demonstrates the feasibility of the laser wavelength measurement using rotating FP method.

Mid-infrared spectroscopy has been an important tool widely used for qualitative analysis in various fields. However, portable or personal use is size and cost prohibitive for either Fourier transform infrared or attenuated total reflectance (ATR) spectrophotometers. In this study, we developed an ultra-compact ATR spectrophotometer whose frequency band was 5.5–11.0 μm. We used miniature components, such as a light source fabricated by semiconductor technology, a linear variable filter, and a pyro-electric array detector. There were no moving parts. Optimal design based on two light sources, a zippered configuration of the array detector and ATR optics could produce absorption spectra that might be used for qualitative analysis. A microprocessor synchronized the pulsed light sources and detector, and all the signals were processed digitally. The size was 13.5×8.5×3.5   cm³ and the weight was 300 grams. Due to its low cost, our spectrophotometer can replace many online monitoring devices. Another application could be for a u-healthcare system installed in the bathroom or attached to a smartphone for monitoring substances in body fluids.

A method of realizing a compact Fourier transform spectrometer is proposed in this work, which is based on the polarization interference in a single layer of birefringent liquid crystal (BLC). The continuous interference between the ordinary light and the extraordinary light is driven by a continuously adjusted electric field. Benefiting from the single-layer configuration with no moving parts, the spectrometer is easily miniaturized. The method to realize the spectrometer is theoretically analyzed and experimentally demonstrated by a layer of nematic BLC with a 100-μm thickness.

An automated data acquisition and processing system is established to measure the force applied by an optical trap to an object of unknown composition in real time. Optical traps have been in use for the past 40 years to manipulate microscopic particles, but the magnitude of applied force is often unknown and requires extensive instrument characterization. Measuring or calculating the force applied by an optical trap to nonspherical particles presents additional difficulties which are also overcome with our system. Extensive experiments and measurements using well-characterized objects were performed to verify the system performance.

An accurate characterization method for a multispectral high-dynamic-range (HDR) imaging system is proposed by combining multispectral and HDR imaging technologies. The multispectral HDR imaging system, which can acquire the visible spectrum at many wavelength bands, can provide an accurate color reproduction and physical radiance information of real objects. An HDR camera is used to capture an HDR image without multiple exposures and a liquid crystal tunable filter (LCTF) is used to generate multispectral images. Due to its several limitations in the multispectral HDR imaging system, a carefully designed and an innovative characterization algorithm is presented by considering a logarithmic camera response of the HDR camera and different spectral transmittance of the LCTF. The proposed method efficiently and accurately recovers the full spectrum from the multispectral HDR images using a transformation matrix and provides device-independent color information (e.g., CIEXYZ and CIELAB). The transformation matrix is estimated by training the estimated sensor responses from a multispectral HDR imaging system and the reflectance measurements from a spectroradiometer using Moore–Penrose pseudoinverse matrix.

An integrated navigation method based on the strapdown inertial navigation system (SINS) and Doppler Lidar was presented and its validity is demonstrated by practical experiments. A very effective and independent integrated navigation mode is realized that both an inertial navigation system (INS) and Lidar are not interfered with or screened by electromagnetic waves. In our work, the SINS error model was first introduced, and the velocity error model was transformed into body reference coordinates. Then the expression for measurement model of SINS/Lidar integrated navigation was deduced under Lidar reference coordinates. For application of land or vehicle navigation, the expression for the measurement model was simplified, and observation analysis was carried out. Finally, numerical simulation and vehicle test results were carried out to validate the availability and utility of the proposed SINS/Lidar integrated navigation method for land navigation.

In fringe projection profilometry, carrier removal is required to obtain the absolute height information of the tested object. We propose using radial basis function interpolation methods, due to their good approximation properties, to accurately remove the carrier phase. We evaluate the proposed method on a simulated fringe projection pattern with a nonlinear carrier and two experimentally obtained fringe projection patterns, respectively. The performance of the proposed method is compared to those of the widely used least-squares method and recent Zernike polynomial fitting method. Experimental results show that the proposed method has an improved performance.

Data centers have to sustain the rapid growth of data traffic due to the increasing demand of bandwidth-hungry Internet services. The current fat tree topology causes communication bottlenecks in the server interaction process, resulting in power-hungry O-E-O conversions that limit the minimum latency and the power efficiency of these systems. As a result, recent efforts have advocated that all optical data center networks (DCNs) have the capability to adapt to traffic requirements on demand. We present the design, implementation, and evaluation of a cascaded microelectromechanical systems switches-based DCN architecture which dynamically changes its topology and link capacities, thereby achieving unprecedented flexibility to adapt to dynamic traffic patterns. We analyze it under a data center traffic model to determine its suitability for this type of environment. The proposed architecture can be scaled to 3300 input/output ports by available experimental components with low blocking probability and latency. The blocking probability and latency are about 0.03 and 72 ms at a moderate traffic load for 32 input/output ports based on our numerical results, which are much smaller than the results for 4 input/output ports which are 0.13 and 235 ms, respectively.

The evolution of Stokes generation up to the n’th stage and the analytical solutions of commonly used Raman equations including numerical simulation and experimental results is reported. For the experimental work, a 1-km un-doped single-mode fiber was pumped with an ytterbium-doped fiber laser system (FL) in CW regime at 1064 nm in a free running configuration. We showed that it is possible to obtain up to the N’th power thresholds and maximum power for each Stokes by using compact analytical solutions as a first approximation in an arguably simple, quick process.

We investigate an acousto-optic tunable filter setup for wavelength division multiplexing telecommunication applications in wideband C (100 nm around 1550 nm). Anisotropic Bragg diffraction of light in TeO₂ bulk crystal is first investigated experimentally and theoretically in a quasi-collinear interaction configuration. Based on those characterizations, we propose a double-pass optical beam which allows us to improve the filter performances in terms of crosstalk and selectivity: the full width at half maximum and the sidelobe level are reduced.

We presented a highly efficient 1×3 optical power splitter based on photonic crystal waveguides (PCWs) with a triangular lattice of air holes. By only modifying a single hole in a Y junction area, the input power can be almost evenly split into three ports. The optimal device can operate with a total transmittance higher than 99% simultaneously at 1384, 1490, and 1550 nm, which are within the E-, S-, and C-bands of optical communication spectra, respectively. It provides a new method and a compact model to split the input power into three channels in PCW devices and can find triple play applications in an optical communication system.

The results of transmitted wavefront distortion correction are presented for a YAG:ND³⁺ active element with a diameter 45 mm. Halftone mask and proximity printing were used for fabrication of the freeform corrector. Experimental results show a three-fold decrease of the wavefront distortion. Because the corrector presented a high damage threshold, it can be used with high power laser systems.

Tool influence function (TIF) is quite important for computer-controlled optical surfacing (CCOS) technology. Quantitatively investigating the error correction ability of TIF in frequency domain is essential for CCOS to restrain different spatial frequency errors. The smoothing spectral function (SSF) is a newly proposed parameter to evaluate the error correction ability of CCOS process. Based on the SSF, a new method to calculate the error correction ability of TIF in certain polishing conditions will be proposed. The basic mathematical model for this method will be established in theory. A set of polishing experiments with rigid conformal (RC) tool are performed to calculate the error correction ability of TIF. The calculated results can quantitatively indicate the error correction ability of TIF for different spatial frequency errors in certain polishing conditions.

A high data transmission rate is the main requirement for next-generation telecommunication networks. A design for a 40  Gb/s time and wavelength-division multiplexed passive optical network (TWDM-PON) for next-generation passive optical network stage 2 is presented. The use of a modulated grating Y-branch (MG-Y) laser is proposed as an upstream tunable colorless laser source to upgrade the optical network unit. The electronically tuned MG-Y externally modulated laser with a 10  Gb/s modulation rate is applied to a TWDM-PON and presented across a 3.2-nm tuning range. The performance of the proposed laser is analyzed in terms of bit error rate, eye diagram, and optical signal-to-noise ratio. The proposed TWDM-PON achieved an aggregated data rate of 40  Gb/s along 40 km of bidirectional fiber at a 1:128 splitting ratio without amplification and dispersion compensation.

For extremely high accuracy optical elements, the residual error induced by the superposition of the tool influence function cannot be ignored and leads to medium-high frequency errors. Even though the continuous computer-controlled optical surfacing process is better than the discrete one, which can decrease this error to a certain degree, the error still exists in scanning directions when adopting the raster path. The purpose of this paper is to optimize the parameters used in bonnet polishing to restrain this error. The formation of this error was theoretically demonstrated and will also be further experimentally presented using our newly designed prototype. Orthogonal simulation experiments were designed for the following five major operating parameters (some of them are normalized) at four levels: inner pressure, z offset, raster distance, H-axis speed, and precession angle. The minimum residual error method was used to evaluate the simulations. The results showed the impact of the evaluated parameters on the residual error. The parameters in descending order of impact are as follows: raster distance, z offset, inner pressure, H-axis speed, and precession angle. An optimal combination of these five parameters among the four levels considered, based on the minimum residual error method, was determined.

In a lossy media, anisotropic chiral metamaterial (MTM) structures with normal incidence asymmetric transmission of linearly polarized electromagnetic (EM) waves are investigated and analyzed in both microwave and terahertz frequency regimes. The proposed lossy structures are used to perform dynamic polarization rotation and consist of square-shaped resonators with gaps on both sides of dielectric substrates with a certain degree of rotation. Asymmetric transmission of a linearly polarized EM wave through the chiral MTMs is realized by experimental and numerical studies. The dynamic structures are adjustable via various parameters to be tuned for any desired frequency regimes. From the obtained results, the suggested structure can be used to design new polarization control devices for desired frequency regimes.

A reconfigurable optoelectronic oscillator (OEO) based on a double-coupling recirculating delay line (DC-RDL) is analyzed and experimentally demonstrated. In the proposed OEO, an incoherent two-tap microwave photonic filter is formed by an amplified spontaneous emission (ASE) source, a Mach–Zehnder modulator, a DC-RDL, and a polarization beam splitter (PBS) to realize selection of the oscillation mode. Specifically, the incoherence is implemented using an ASE broadband laser source and a DC-RDL, and the high sidemode suppression performance can be achieved by employing the dual-loops system between the dual output of the DC-RDL and the PBS. A detailed theoretical analysis is provided and is verified by the experiment. The single-sideband phase noise, the frequency tunability, and the long-term stability of the generated microwave signal are investigated. In addition, the frequency independent of the phase noise is also experimentally observed.

According to the defect of the high peak-to-average-power ratio (PAPR) in optical orthogonal frequency division multiplexing (OFDM) systems, the PAPR reduction technology based on the partial transmission sequences (PTS) method has been deeply studied. An improved enhanced-iterative-algorithm-PTS (EIA-PTS) technology is proposed. The proposed EIA-PTS technology, compared with the original PTS (O-PTS), can reduce the computational complexity. The simulation analysis shows that the computational complexity of the O-PTS method grows exponentially with an increase in the number of both subblocks and phase factors, while the computational complexity of the EIA-PTS technology basically remains stable and is lower than that of the O-PTS method. On the basis of the proposed EIA-PTS technology, an improved EIA-PTS-Clipping combined PAPR reduction technology that combines EIA-PTS technology with clipping technology is proposed. The simulation result shows the proposed EIA-PTS-Clipping combined PAPR reduction technology, compared with the previous proposed EIA-PTS technology, can further improve the PAPR reduction performance and has a higher application value because it can have a better tradeoff between the bit error rate performance and PAPR reduction effect for optical OFDM systems.

The compression characteristics of a passive self-similar compressor consisting of a dispersion-decreasing fiber (DDF) and a compensative fiber are numerically investigated. The results show that the group-velocity dispersion (GVD) of the compensative fiber has a periodic influence on the compression factor and peak power of the compressed pulse. That is, the pulse energy is concentrated, then dispersed, and then concentrated again periodically. Every time the energy is concentrated, the pulse width reaches its compression limit. With the increase of the GVD value of the compensative fiber, the period interval increases and more energy is transferred within a period. On the other hand, an increase of the nonlinearity of the compensative fiber leads to a decrease of the compression factor, which is not conducive to pulse compression. Moreover, the degree of self-similar evolution is decided by the length of the DDF. A suitable evolution degree and optimal DDF length cause the pulse to reach a maximum compression limit. In addition, the optimal compensative fiber length increases with the degree of self-similar evolution and decreases with the GVD value of the compensative fiber, although it has nothing to do with the nonlinearity of the compensative fiber. By optimizing the parameters of the compensative fiber and the length of the DDF, the pulse width attains a compression limit and a high-quality pulse is obtained.

Simple and complete empirical relations are presented here to determine a normalized spot size in terms of normalized frequencies over a long range and aspect ratio of a trapezoidal index single-mode fiber considering Gaussian approximation of the fundamental mode following the Marcuse method for the first time. After verification of their validity for arbitrary values of aspect ratio and normalized frequency, we calculate various propagation characteristics viz. dispersion and splice loss by using our formulations. Upon comparison, we observe an excellent match and the validity of our results with exact values and other results available in the literature. These formulas should attract the attention of experimentalists as a simple alternative to the rigorous methods of estimating the propagation characteristics of such fibers.

We propose an accurate analytical model to calculate the optical crosstalk of a first-order free space optical interconnects system that uses microlenses with circular apertures. The proposed model is derived by evaluating the resulted finite integral in terms of an infinite series of Bessel functions. Compared to the model that uses complex Gaussian functions to expand the aperture function, it is shown that the proposed model is superior in estimating the crosstalk and provides more accurate results. Moreover, it is shown that the proposed model gives results close to that of the numerical model with superior computational efficiency.

Free-space optics (FSO) has become one of the prominent solutions to the bandwidth limitation of radio frequency links. But, the FSO system performance is purely dependent on atmospheric conditions. Atmospheric turbulence, scintillation, and pointing errors are the major deteriorations in FSO communications. Multiple input multiple output (MIMO) or spatial diversity structure can improve the performance of the FSO system. The bit error rate (BER) performance of the MIMO FSO system employing binary polarization shift keying using optimal combining is analyzed. We have derived a closed form expression for the BER of the system, and the results are compared against the single input single output system.

A defected core decagonal photonic crystal fiber is designed and numerically optimized to obtain its residual chromatic dispersion compensation in the wavelength range of 1460 to 1675 nm i.e., over S+C+L+U wavelength bands having an average dispersion of about −390  ps/(nm km) with a dispersion variation of 7  ps/(nm km). The designed fiber, with a flattened dispersion profile, has four rings of holes in the cladding region, which results in low confinement loss and small effective mode area at wavelength 1550 nm. For residual chromatic dispersion compensation, the proposed fiber can be used in wavelength division multiplexing optical fiber data communication systems.

A method for high-bit-rate optical pulse amplification without a pattern effect (PE) phenomenon is numerically analyzed and presented. In the proposed new scheme, the input signals are applied to a series of 1×2 optical switches and semiconductor optical amplifiers (SOAs). Based on the input signal bit rate and the desired PE reduction rate, it is shown that the number of these devices can be easily optimized. For reducing the SOA nonlinearities on the output signal, a high-birefringent fiber loop mirror is used as an optical Gaussian filter. The achieved results depict that symmetry and the time-bandwidth product of the output signal obtained by this filter are significantly improved. The simulations are performed for high bit-rate signals (<50  Gbps); therefore, in the SOA model, all relevant nonlinear effects that occur in the subpicosecond regimes are taken into account.

Ultrafast Bessel beams are ideal sources for high aspect ratio submicron structuring applications because of their nondiffracting nature and higher stability in nonlinear propagation. We report here on the interaction of ultrafast Bessel beams at various laser energies and pulse durations with transparent materials (fused silica) and define their impact on photoinscription regimes, i.e., formation of positive and negative refractive index structures. The laser pulse duration was observed to be key in deciding the type of the structures via excitation efficiency. To understand the relevant mechanisms for forming these different structures, the free carrier behavior as a function of laser pulse duration and energy was studied by capturing instantaneous excitation profiles using time-resolved microscopy. Time-resolved imaging and simulation studies reveal that low carrier densities are generated for ultrashort pulses, leading to soft positive index alterations via presumably nonthermally induced structural transitions involving defects. On the other hand, the high free carrier density generation in the case of longer pulse durations leads to hydrodynamic expansion, resulting in high aspect ratio submicron-size wide voids. Delayed ionization, carrier defocusing, and lower nonlinear effects are responsible for the confinement of energy, resulting in efficient energy deposition on-axis.

Quadrature duobinary (QDB) spectrum shaping polarization division multiplexed-quadrature phase shift keying (PDM-QPSK) signal with Nyquist and super-Nyquist spectrum efficiency will be a promising candidate for future ultrahigh speed ultrahigh spectrum efficiency coherent optical fiber transmissions systems. Several equalization algorithms including constant modulus algorithm (CMA), CMA plus postfilter, and cascaded multimodulus algorithm (CMMA) have been proposed as effective solutions for QDB-PDM-QPSK signal. For the first time as far as we know, the application conditions and performances for these three algorithms are analyzed and compared. System performances for a 112-Gb/s QDB-PDM-QPSK signal as a function of the optical filtering bandwidth and the optical SNR have been theoretically investigated. The results show that CMA would be the best choice in terms of convergence rate for general filtering. However, CMMA can outperform the other two schemes with a good receiver sensitivity and high-dynamic range of optical signal to noise ratio giving a strong filtering effect of super-Nyquist signaling.

A two-dimensional (2-D) photonic quasicrystal (PQC) flat lens with three scatterers is proposed, and its focusing characteristics for a point source are analyzed for the case of a continuously changing scatterer radius. The results show that a super-lens can be formed by three scatterers, and there is a threshold for scatterer radius. The focusing characteristics of the flat lens within the focusing radius are changed with regularity. It is reported for the first time that best image quality and the stability of perfect imaging in this 2-D PQC flat lens with three scatterers are superior to those in 2-D PQC or periodic photonic crystal flat lenses with multiple scatterers.

We demonstrate a flexible organic light-emitting device (OLED) by using silver nanowire (AgNW) transparent electrode. A template stripping process has been employed to fabricate the AgNW electrode on a photopolymer substrate. From this approach, a random AgNW network electrode can be transferred to the flexible substrate and its roughness has been successfully decreased. As a result, the devices obtained by this method exhibit high efficiency. In addition, the flexible OLEDs keep good performance under a small bending radius.

We present the implementation and validation of low-coherence Fabry–Perot interferometer for refractive index dispersion measurements of liquids. A measurement system has been created with the use of four superluminescent diodes with different optical parameters, a fiber-optic coupler and an optical spectrum analyzer. The Fabry–Perot interferometer cavity has been formed by the fiber-optic end and mirror surfaces mounted on a micromechanical stage. The positive result of the validation procedure has been determined through statistical analysis. All obtained results were 99.999% statistically significant and were characterized by a strong positive correlation (r<0.98). The accuracy of the measured result of implemented low-coherence Fabry–Perot interferometer sensor is from 83% to 94%, which proves that the sensor can be used in the measurement of refractive index dispersion of liquids.

An optical fiber corrosion sensor (OFCS) based on iron-carbon (Fe-C) film was researched. OFCS was formed by electroplating a Fe-C film on fiber Bragg grating (FBG) metalized with silver film by magnetron sputtering. There was a more than 430-pm change of FBG wavelength when Fe-C film was seriously corroded. Compared to electrochemical method, the optical fiber sensor shows dominance in long-lasting monitoring of corrosion. The electric signal was broken off after the 20-h corrosion of Fe-C film, while the optical fiber sensor’s monitoring lasted more than 40 days.