A new method to count the expected value and variance of time dispersion is presented for time dispersion of underwater optical wireless communication. Instead of the typically used Gamma distribution, inverse-Gaussian distribution is suggested for underwater optical impulse response time waveform function. The expectation of this method is in good agreement with experimental data. Future works may include water absorption to the model.

Using transmitting volume Bragg gratings (TVBG) as a basis, an experiment on one-dimensional spatial filtering of a deformed laser beam is designed. The deformed laser beam results from a He-Ne laser beam modulated by an amplitude modulation plate with a spatial frequency of 7.2 mm ?1. Results show that when the central wave vector of the deformed beam satisfies the Bragg law of TVBG, the spatial profile of the -1st forward-diffracted order is similar to that of the undeformed He-Ne laser beam due to the TVBG with a spatial frequency selective bandwidth of less than 5.0 mm?1. The higher frequency components of the deformed beam are filtered out in the optical near field. Thus, the TVBG cleanup of the spatiallydeformed laser beam is realized experimentally.

We numerically study the propagation of 1-ps laser pulse in three tapered holey fibers (THFs). The curvature indices of the concave, linear, and convex tapers are 2.0, 1.0, and 0.5, respectively. The central wavelength, located in the normal dispersion regime, is 800 nm. The nonlinear coefficient of the THFs increases from the initial 0.095 m

We study an electronic compensator (EC) as a receiver for a 100-Gb/s polarization division multiplexing coherent optical orthogonal frequency division multiplexing (PDM-CO-OFDM) system without optical dispersion compensation. EC, including electrical dispersion compensation (EDC), least squares channel estimation and compensation (LSCEC), and phase compensation (PC), is used to compensate for chromatic dispersion (CD), phase noise, polarization mode dispersion (PMD), and channel impairments, respectively. Simulations show that EC is highly effective in compensating for those impairments and that the performance is close to the theoretical limitation of optical signal-to-noise rate (OSNR), CD, and PMD. Its robustness against those transmission impairments and fiber nonlinearity are also systematically studied.

We demonstrate an all-optical reconfigurable logic gate based on dominant nonlinear polarization rotation accompanied with cross-gain modulation effect in a single semiconductor optical amplifier (SOA). Five logic functions, including NOT, OR, NOR, AND, and NAND, are realized using 10-Gb/s on-off keying signals with flexible wavelength tunability. The operation principle is explained in detail. By adjusting polarization controllers, multiple logic functions corresponding to different input polarization states are separately achieved using a single SOA with high flexibility.

The dynamics of dark-bright vector solitons is investigated in a birefringent fiber with the high-order dispersions, and their effects on vector soliton propagation and interaction are analyzed using the numerical method. The combined role of the high-order dispersions, such as the third-order dispersion (TOD) and the fourth-order dispersion (FOD), may cause various deformation of the vector soliton and enhance interaction. These effects depend strictly on the sign of the high-order dispersions. Results indicate that the disadvantageous effects can be reduced effectively via proper mapping of the high-order dispersions.

A non-invasive detection method for the status analysis of cell culture is presented based on digital holography technology. Lensless Fourier transform digital holography (LFTDH) configuration is developed for living cell imaging without prestaining. Complex amplitude information is reconstructed by a single inverse fast Fourier transform, and the phase aberration is corrected through the two-step phase subtraction method. The image segmentation is then applied to the automatic evaluation of confluency. Finally, the cervical cancer cell TZMbl is employed for experimental validation, and the results demonstrate that LFTDH imaging with the corresponding image post-processing can provide an automatic and non-invasive approach for monitoring living cell culture.

We present a spiral phase filtering system with a large tolerance for edge enhancement of both phase and amplitude objects in optical microscopy. The method is based on a Fourier 4-f spatial filtering system. A phase mismatched spiral phase plate (SPP) fabricated by electron beam lithography is employed as the radial Hilbert transform for image edge enhancement. Compared with holography, SPP is simple, economical, reliable, and easy to integrate.

To apply decision level fusion to hyperspectral remote sensing (HRS) image classification, three decision level fusion strategies are experimented on and compared, namely, linear consensus algorithm, improved evidence theory, and the proposed support vector machine (SVM) combiner. To evaluate the effects of the input features on classification performance, four schemes are used to organize input features for member classifiers. In the experiment, by using the operational modular imaging spectrometer (OMIS) II HRS image, the decision level fusion is shown as an effective way for improving the classification accuracy of the HRS image, and the proposed SVM combiner is especially suitable for decision level fusion. The results also indicate that the optimization of input features can improve the classification performance.

We propose a new analytical edge spread function (ESF) fitting model to measure the modulation transfer function (MTF). The ESF data obtained from a slanted-edge image are fitted to our model through the non-linear least squares (NLLSQ) method. The differentiation of the ESF yields the line spread function (LSF), the Fourier transform of which gives the profile of two-dimensional MTF. Compared with the previous methods, the MTF estimate determined by our method conforms more closely to the reference. A practical application of our MTF measurement in degraded image restoration also validates the accuracy of our model.

An efficient and inexpensive method that uses a glass plate mounted onto a motorized rotating stage as a beam-steering device for the generation of dynamic optical traps is reported. Force analysis reveals that there are drag and trapping forces imposed on the bead in the opposite directions, respectively, in a viscous medium. The trapped bead will be rotated following the beam’s motion before it reaches the critical escape velocity when the drag force is equal to the optical trapping force. The equilibrium condition facilitates the experimental measurement of the drag force with potential extensions to the determination of the viscosity of the medium or the refractive index of the bead. The proposed technique can easily be integrated into conventional optical microscopic systems with minimum modifications.

We develop and build a new type of inspection car. A beam that is not rigidly connected to the train axle boxes and can absorb the vibration and impact caused by the high speed train is used, and a laser-camera measurement system based on the machine vision method is adopted. This method projects structural light onto the track and measures gauge and longitudinal irregularity. The measurement principle and model are discussed. Through numerous practical experiments, the rebuilt car is found to considerably eliminate the measurement errors caused by vibration and impact, thereby increasing measurement stability under high speeds. This new kind of inspection cars have been used in several Chinese administration bureaus.

The principle of optical eigenfunction is used in the analysis of speckle reduction in laser projection display. When the moving diffuser is used in the speckle reduction approach, the speckle contrast is decided by both the degree of freedom (DOF) of the projector and the area of resolving cell of the eyes on the screen. It can gain high DOF of the projector by increasing the space-bandwidth product, i.e., adopting a projection lens with a high numerical aperture or a large viewing field. The best scheme is equalizing the DOF of the scattering wave from a moving diffuser to that of the projection lens. The experimental results are in accordance with the conclusion drawn by optical eigenfunction.

We demonstrate a multiple wavelength Brillouin/erbium fiber laser in a linear cavity configuration. The laser cavity is made up of a fiber loop mirror on one end of the resonator and a virtual mirror generated from the distributed stimulated Brillouin scattering effect on the other end. Due to the weak reflectivity provided by the virtual mirror, self-lasing cavity modes are completely suppressed from the laser cavity. At Brillouin pump and 1480-nm pump powers of 2 and 130 mW, respectively, 11 channels of the demonstrated laser with an average total power of 7.13 dBm can freely be tuned over a span of 37-nm wavelength from 1530 to 1567 nm.

We report an all-fiber high power, single frequency large-mode area (LMA) linearly polarized ytterbiumdoped fiber amplifiers (YDFA) module, which is based on the master oscillator multi-stage power amplifiers (MOPA). The maximum output power is 43.8 W at a wavelength of 1064 nm when 60-W launched pump light is coupled, with high slope efficiency of 88%, polarization extinction rate (PER) >17.2 dB and nearly diffraction-limited beam quality (M2<1.1).

An optimized dual fiber Bragg grating (FBG) is proposed for 980-nm semiconductor lasers without thermoelectric coolers to restrict temperature-induced wavelength shift. The mathematical model of the temperature-induced wavelength shift of the laser with the dual FBG is built using the external cavity feedback rate equations. The external cavity parameters are optimized for achieving the stability mode-locking laser output. The spectral characteristics of the dual FBG stabilized laser are measured to range from 0 to 70 oC. The side mode suppression ratio (SMSR) is more than 45 dB, while the full-width at half-maximum (FWHM) is less than 1 nm. The peak wavelength shift is less than 0.1 nm. The dual FBG wavelength shift proportional coefficient is between 0.1086 and 0.4342.

We experimentally demonstrate a fast random bit generator (RBG) based on bandwidth-enhanced chaotic laser from an optical feedback laser diode with optical injection. The bandwidth-enhanced chaotic signal is sampled and converted to a binary sequence in real time without the need of programming for off-line processing. Multi-rate bit sequences, with the fastest rate of up to 2.87 Gb/s, are obtained with verified randomness.

We investigate the aberration properties of the conformal optical system with decentered and tilted elements by vector aberration theory. By decentering and tilting the window and corrector of the system, two elements are effectively used together in a particular manner by aberration compensation to achieve off-axis imaging. A conceptual design is performed with a half-field of 2?, the F# of 4, and the wavelength ranging of 3700~4800 nm. The imaging quality can reach the optical diffraction limit and satisfy corresponding requirements.

Amino-functionalized mesoporous silica thin films (MTFs) are produced using surface active agent F127, and then gold nanoparticles are introduced into the pore channels to prepare the Au/SiO2 nanocomposite. After assembling the gold, the amino-functionalized MTF undergoes some shrinkage but remains a periodic structure as demonstrated by X-ray diffraction (XRD) patterns. The nanocomposite shows an acute characteristic diffraction peak assigned to (111) plane of the face-centered-cubic structure of gold, indicating that gold nanoparticles crystallize well and grow in a preferred orientation in the pore channels. The surface plasma resonance (SPR) absorption peak near 570 nm undergoes a red-shift accompanied by a strengthening of intensity when HAuCl4 is used to react with the amino groups on the internal pore surfaces for 4, 6, and 8 h. The simulative results are consistent with the experimental ones shows that the absorption property of the Au/SiO2 nanocomposite is influenced by the dipping time, which affects the size and volume fraction of embedded gold nanoparticles.

Frequency tunable continuous variable (CV) entangled optical beams are experimentally demonstrated from a non-degenerate optical parametric oscillator working above the threshold. The measured correlation variances of amplitude and phase quadratures are 3.2 and 1.5 dB, respectively, below the corresponding shot noise level (SNL) in the tuning range of 580 GHz (2.25 nm). The frequency tuning is realized by simply controlling the temperature of the nonlinear crystal.

The security of the quantum secret key plays a critical role in quantum communications. Thus far, one problem that still exists in existing protocols is the leakage of the length of the secret key. In this letter, based on variable quantum encoding algorithms, we propose a secure quantum key distribution scheme, which can overcome the security problem involving the leakage of the secret key. Security analysis shows that the proposed scheme is both secure and effective.

Forward-scattering efficiency (FSE) is first proposed when an Ag nanoparticle serves as the light-trapping structure for thin-film (TF) solar cells because the Ag nanoparticle’s light-trapping efficiency lies on the light-scattering direction of metal nanoparticles. Based on FSE analysis of Ag nanoparticles with radii of 53 and 88 nm, the forward-scattering spectra and light-trapping efficiencies are calculated. The contributions of dipole and quadrupole modes to light-trapping effect are also analyzed quantitatively. When the surface coverage of Ag nanoparticles is 5%, light-trapping efficiencies are 15.5% and 32.3%, respectively, for 53- and 88-nm Ag nanoparticles. Results indicate that the plasmon quadrupole mode resonance of Ag nanoparticles could further enhance the light-trapping effect for TF solar cells.

Nondestructive Raman spectroscopy and external-beam proton-induced X-ray emission (PIXE) technique to analyze eight ancient glasses unearthed from the provinces of Henan, Hubei, and Jiangsu, which allowes for a good characterization of the glass matrix and chemical compositions, is carried out. The results indicate that all the eight glass samples could be typically divided into three systems: faience (sample No. SZWG-4), PbO-BaO-SiO2 (sample Nos. NYWKI-5-1, HNWKII-88, and HNWKII-84), and Na2OCaO-SiO2 (sample Nos. HBWKI-16, HBWKI-17, HBWKI-18, and SZWG-1). Additional relationships between the Raman spectra and parameters, such as residues of raw materials and opacifying agent, are also discussed by respectively comparing them with similar glass samples excavated from other historical sites.

Ultra-narrow linewidth, nonpolarizing guide-mode resonance (GMR) filters with single and double common resonance wavelengths are designed. The guide-mode resonance filters consist of a single grating layer with asymmetric profiles. By choosing appropriate parameters, same resonance wavelengths for both transverse electric (TE) and transverse magnetic (TM) polarizations can be achieved. Results show that high reflection (more than 99.9%) is obtained at every resonance wavelength, and the full-width at half-maximums (FWHMs) of TE- and TM-polarized light are only 0.008 and 0.215 nm, respectively.

Specified ultra-short pulse waveforms could be synthesized with high-resolution zero-dispersion pulse shaping system. The system and parameters are analyzed and discussed. The pulse shaping system with optimized parameters could resolve the frequency components of ultra-broad bandwidth pulse and prevent the spatial shaping of individual frequency components. The specified waveforms, Meyer wavelet and square root raised cosine pulses, are generated with programmable amplitude and phase masks.