A two-dimensional model of a metal-semiconductor-metal (MSM) ZnO-based photodetector (PD) is developed. The PD is based on a drift diffusion model of a semiconductor that allows the calculation of potential distribution inside the structure, the transversal and longitudinal distributions of the electric field, and the distribution of carrier concentration. The ohmicity of the contact has been confirmed. The dark current of MSM PD based ZnO for different structural dimensions are likewise calculated. The calculations are comparable with the experimental results. Therefore, the influence with respect to parameters s (finger spacing) and w (finger width) is studied, which results in the optimization of these parameters. The best optimization found to concur with the experimental results is s = 16 \mu m, w = 16 \mu m, l = 250 \mu m, L = 350 \mu m, where l is the finger length and L is the length of the structure. This optimization provides a simulated dark current equal to 24.5 nA at the polarization of 3 V.

A design of polarization-maintaining retro-reflectors (PMRRs) for folded-path applications is proposed and analyzed. The prism-based scheme enables the output light, which is parallel to the input, to have an identical state of polarization. The principle of the design is theoretically verified, and the related error is analyzed due to possible manufacturing imperfection. The maximum spatial angle error is +-2.75o. The effect on the extinction ratio and insertion loss is also discussed, which further proves the design's feasibility in practical applications.

We present the numerical results of both head-on and non-head-on collisions between two stable dissipative optical bullets (DOBs) in a three-dimensional complex Ginzburg-Landau equation with cubic-quintic nonlinearity. The system parameters chosen are in the coexistence regions for both stationary DOBs and double bullet complexes (DBCs). By varying the initial velocities v and the impact parameters P which represent the distance between the parallel trajectories of colliding bullets, we observe three generic properties of the bullets: fusion, fission, and quasi-elastic collisions. A novel and interesting behavior is observed in the results, in which two or three DBCs occur in non-head-on collisions at intermediate values of v.

Path protections have become increasingly important for current mesh optical networks because fast restorations in generalized multiprotocol label switching (GMPLS) networks are uncertain. However, setting up additional disjoint paths to protect connections leads to more path setup blocking and signaling collisions. We analyze signaling collisions, path blocking and blocking probability, as well as calculate node-to-node blocking probabilities. A signaling-based path-segment protection (PSP) is proposed, which integrates segment protections and path protections as well as enhances the performance of path protections and ring protections. The setup of PSP connections causes less blocking probability than the setup of path protection connections in the simulations.

A compact fiber Bragg grating (FBG) diaphragm accelerometer based on L-shaped rigid cantilever beam is proposed and experimentally demonstrated. The sensing system is based on the integration of a flat diaphragm and an L-shaped rigid cantilever beam. The FBG is pre-tensioned and the two side points are fixed, efficiently avoiding the unwanted chirp effect of grating. Dynamic vibration measurement shows that the proposed FBG diaphragm accelerometer provides a wide frequency response range (0–110 Hz) and an extremely high sensitivity (106.5 pm/g), indentifying it as a good candidate for embedding structural health monitoring and seismic wave measurement.

A multimode fiber-optic surface plasmon resonance (SPR) sensor with a MgF2 film as a modulated layer is studied. The fiber-optic SPR sensor is investigated theoretically, specifically the influence of the dielectric protecting layer, using a four-layer model. The sensor is then fabricated with the optimal parameters suggested by the theoretical simulation. The sensor has a high sensitivity in the analyte refractive index (RI) range of 1.33-1.40. The best sensitivity of 4 464 nm/RIU is achieved in the experiment. The use of dielectric film (MgF2) can not only modulate the resonance wavelength of the sensor, but also protect the silver film from oxidation.

A spectral amplitude coded-optical code division multiplexing time division multiplexing (SAC-OCDM/TDM) passive optical network (PON) for upgrading the traditional TDM PON is proposed. To the best of our knowledge, our work is the first to report on the use of both spectral and orthogonal code domains, which are transparent to optical network unit (ONU) for hybrid PON, in order to upgrade TDM PON seamlessly. The fewer encoder/decoders and cheaper optical source under the conditions of high bite rate and large ONU accommodation make the system cost-effective. A downstream experiment is demonstrated, and the results demonstrate that the proposed system is feasible.

Using differential detection, we perform polarization-multiplexing 160-Gb/s optical non-return-to-zero (NRZ) differential quadrature phase shift keying (DQPSK) signal transmission over 100-km standard single mode fiber at a bit error rate (BER) of less than 10-9. The enabling technology includes clock recovery, fine dispersion compensation, and polarization tracking for de-multiplexing. Furthermore, a hybrid clock recovery scheme is proposed. The scheme is realized with ordinary devices using an optoelectrical modulator to down-convert the clock frequency and a phase-locked loop for filtering, which can provide an indication signal that simultaneously monitors residual dispersion and tracking polarization.

We demonstrate a glucose fiber sensor for measuring glucose concentration in serum. High resolution and rapid measurement are achieved through the integration of highly selective enzymes and heterodyne interferometry. The best resolution and response time obtained are 0.14 mg/dL and 1.3 s, respectively. The stability of the sensor is also verified by investigating the initial phase variation. Experimental results show that the fiber sensor can be reused more than 10 times.

A new highly birefringent octagonal photonic crystal fiber (Hi-Bi OPCF) with a rectangular array of four elliptical airholes in the fiber core region is proposed and analyzed using the full-vector finite element method with anisotropic perfect match layer absorbing boundaries. Numerical results show that the phase birefringence of the photonic crystal fiber (PCF) reaches 3.43￡10 2 at the wavelength of 1 550 nm. Moreover, two zero-dispersion wavelengths are achieved in the visible and near infrared wavelength regions for one polarization state but not in the other.

A novel precise force measurement based on a Y-shaped cavity dual-frequency laser is proposed. The principle of force measurement with this method is analyzed, and the analytic relation expression between the input force and the change in the output beat frequency is derived. Experiments using a 632.8-nm Y-shaped cavity He-Ne dual-frequency laser are then performed; they demonstrate that the force measurement is proportional to a high degree over almost five decades of input signal range. The maximum scale factor is observed as 5.02 \times 10^9 Hz/N, with beat frequency instability equivalent resolution of 10^{-5} N. By optimizing the optical and geometrical parameters of the laser sensor, a force measurement resolution of 10^{-6} N could be expected.

A non-scanning, non-interferometric, three-dimensional (3D) optical profilometer based on geometric optics, critical angle principle, and the use of a charge-coupled device (CCD) camera is presented. The surface profile of the test specimen can be transferred into the reflectance profile. The reflectance profile, obtained from a CCD, is the ratio of the intensity at the critical angle to the intensity obtained at the total internal reflection angle. The optical profilometer provides a sub-micron measuring range with nanometer resolution and can be used to measure roughness or surface defects in real time.

Coherent beam combination (CBC) of laser arrays is an efficient way to scale brightness. We demonstrate CBC of two slab laser amplifiers based on active phase locking. Instead of the complex phase detection system, intensity detection is used and the feedback control signal is calculated based on the stochastic parallel gradient descent (SPGD) algorithm. The experimental investigation on a 101.5-W CBC of two slab amplifiers shows that the entire system in a closed loop performs well for long-time observation. A combination efficiency of nearly 81% is realized. The slab amplifier laser arrays are the coherent beams efficiently combined by active phase locking based on the SPGD.

We report on a radially polarized and passively Q-switched Nd:YAG/Cr4+:YAG laser. The bulk Nd:YAG crystal is bonded with two undoped YAG crystal end caps to weaken the thermal lens e ect and thus, enhance the extraction of stored energy in the bulk gain material. In the absence of active water cooling, the average laser power reaches 383 mW with 33% slope e±ciency, and the laser pulse achieves 1.457-W peak power, 18.9-ns duration, and 13.9-kHz repetition rate with 97.6% polarization purity.

A diffusion theory model induced by a line source distribution is presented for oblique-incidence reflectometry. By fitting to this asymmetric diffusion model, the absorption and reduced scattering coefficients \mu_a and μ^'_s of the turbid medium can both be determined with accuracy of 10% from the absolute profile of the diffuse reflectance in the incident plane at the negative position –1.5 transport mean free path (mfp') away from the incident point; particularly, μ^'_s can be estimated from the data at positive positions within 0–1.0 mfp' with 10% accuracy. The method is verified by Monte Carlo simulations and experimentally tested on a phantom.

A new type of optical parametric chirped pulse amplifier is designed and analyzed for the amplification of pulse centered at 808 nm. A novel crystal, yttrium calcium oxyborate YCa₄O(BO₃)₃ (YCOB), is utilized in the power amplification stage of optical parametric amplification (OPA). Noncollinear phase matching parameters in the xoz principle plane of YCOB, compared with those in BBO and DKDP, are analyzed by numerical simulation. The results show that YCOB rather than DKDP can be used in the power amplification stage of OPA to realize the amplification of chirped pulse to several joules with a gain bandwidth exceeding 100 nm. This can be used to gain a high intensity pulse of ~10 fs after the compressor.

Two-photon absorption (2PA) in zinc sulphide (ZnS) and Mn2+-doped ZnS quantum dots is reported by the z-scan technique, with nanosecond pulsed laser radiation at 355 nm. The observed values of the 2PA cross section of all the samples are 105 times larger than that of bulk ZnS.

Antimony-based bismuth-doped thin film, a new kind of super-resolution mask layer, is prepared by magnetron sputtering. The structures and optical constants of the thin films before and after annealing are examined in detail. The as-deposited film is mainly in an amorphous state. After annealing at 170–370 oC, it is converted to the rhombohedral-type of structure. The extent of crystallization increased with the annealing temperature. When the thin film is annealed, its refractive index decreased in the most visible region, whereas the extinction coefficient and reflectivity are markedly increased. The results indicate that the optical parameters of the film strongly depend on its microstructure and the bonding of the atoms.

A new process of magnetorheological figuring (MRF) based on the deliquescence theory is proposed to finish KDP crystals. A novel, non-aqueous, and abrasive-free magnetorheological (MR) fluid is explored, and polishing experiments are performed on a self-developed MRF machine. The removal mechanism is reckoned to be the result of a combination of dominant chemical etching and accessorial mechanical drag. The results indicate that the surface roughness of I plate KDP of 80×80 (mm) polished by MRF is 1.2 nm (root mean square (RMS)), and the tool marks are completely removed. The surface accuracy by MRF is 0.035\lambda (RMS), and the low/middle-frequency errors are significantly corrected after MRF.

The long trace profiler (LTP) is proposed to measure radius of curvature (R) and surface figure of a longradius spherical surface in an optical shop. Equipped with a motorized rotary stage and a two-dimensional tilt stage, the LTP scans the full aperture and calculates the absolute radius of curvature of each scanning line based on the least square method. Nonlinear error and manufacture error difference between center and the edge are obtained by comparing R results. The R-limit is validated and expressed as D/R, where D is the aperture of the mirror under test. A full-aperture three-dimensional figure is also reconstructed based on triangle interpolation.

Retrieving snow surface reflectance is difficult in optical remote sensing. Hence, this letter evaluates five surface reflectance models, including the Ross-Li, Roujean, Walthall, modified Rahman and Staylor models, in terms of their capacities to capture snow reflectance signatures using ground measurements in Antarctica. The biases of all the models are less than 0.0003 in both visible and near-infrared regions. Moreover, with the exception of the Staylor model, all models have root-mean-square errors of around 0.02, indicating that they can simulate the reflectance magnitude well. The R2 performances of the Ross-Li and Roujean models are higher than those of the others, indicating that these two models can capture the angle distribution of snow surface reflectance better.

Samples with nodular defects grown from gold nanoparticles are prepared, and laser-induced damage tests are conducted on them. Nodular defects, which are in critical state of damage, are cross-sectioned by focusing on the ion beam and by imaging using a field emission scanning electron microscope. The crosssectional profile shows that cracks are generated and propagated along the nodular boundaries and the HfO2/SiO2 interface, or are even melted. The thermomechanical process induced by the heated seed region is analyzed based on the calculations of temperature increase and thermal stress. The numerical results give the critical temperature of the seed region and the thermal stress for crack generation, irradiated with threshold fluence. The numerical results are in good agreement with the experimental ones.

Intrinsic zinc oxide films, normally deposited by radio frequency (RF) sputtering, are fabricated by direct current (DC) sputtering. The oxygen-deficient targets are prepared via a newly developed double crucible method. The 800-nm-thick film obtaines significantly higher carrier mobility compareing with that of the 800-nm-thick ZnO film. This is achieved by the widely used RF sputtering, which favors the prevention of carrier recombination at the interfaces and reduction of the series resistance of solar cells. The optimal ZnO film is used in a Cu (ln, Ga) Se2 (CIGS) solar cell with a high efficiency of 11.57%. This letter demonstrates that the insulating ZnO films can be deposited by DC sputtering from oxygen-deficient ZnO targets to lower the cost of thin film solar cells.

The accumulation effects in high-reflectivity (HR) HfO2/SiO2 coatings under laser irradiation are investigated. The HR HfO2/SiO2 coatings are prepared by electron beam evaporation at 1 064 nm. The laser-induced damage threshold (LIDT) are measured at 1 064 nm and at a pulse duration of 12 ns, in 1-on-1 and S-on-1 modes. Multi-shot LIDT is lower than single-shot LIDT. The laser-induced and native defects play an important role in the multi-shot mode. A correlative theory model based on critical conduction band electron density is constructed to elucidate the experimental phenomena.