We report the dark blue nonlinear Cerenkov radiation by the second harmonic generation (SHG) in a two-layer-stacked hexagonal periodically-poled-MgO: LiNbO3s (PPMgOLNs). Based on the direct wafer bonding of two target PPMgOLNs rotating around the axis perpendicular to the plane with an angle of 30o, twelve bright spots as twice of those in a single PPMgOLN are shown at each second-harmonic C erenkov ring. The experimental results agree with the theoretical ones and present a promising application in the fabrication of three-dimensional (3D) PPMgOLNs.

By investigating the influence of the difference of refractive index between core and cladding (nco-ncl), normalized frequency (V ) and core radius (α) on both the intramodal and intermodal nonlinear coefficients (NCs) respectively, we design a novel weakly-coupled four-mode fiber with low nonlinearity. In general, under the premise of ensuring the low NCs between two non-degenerate modes, this design can reduce the intermodal NCs (< 0.5 W-1 \cdot km-1) between two degenerate modes and optimizes the parameters of differential group delays (DGDs) and chromatic dispersion. The optimized few mode fiber (FMF) is eligible for transmission and mode de-multiplexing in the receiver.

A parallel multichannel format conversion scheme for elastic optical networking based on four wave mixing (FWM) in symmetric highly nonlinear fiber loop (S-HNLF-L) is proposed and the performance is evaluated and discussed. Parallel four channels format conversion from quadrature phase shift keying (QPSK) to binary phase shift keying (BPSK) signals at 40 Gb/s is theoretically analyzed and simulated. The results are helpful for the format-adaptive elastic optical networks.

We introduce an idea of producing an optical lattice relied on the Talbot effect. Our alternative scheme is based on the interference of light behind a diffraction grating in the near-field regime. We demonstrate 1D and 2D optical lattices with the simulations and experiments. This Talbot optical lattice can be broadly used from quantum simulations to quantum information. The Talbot effect is usually used in lensless optical systems, therefore it provides small aberrations.

According to the LED spectra measured in the rated current, Gauss distribution function and asymmetric Gaussian distribution function methods are used to simulate the individual LED spectrum. Based on this mathematical model, 32 LEDs are used to synthesize arbitrary spectral distribution of the light source. Processing the spectral data with multiple linear regressions, CIE illuminant A and CIE illuminant D65 are simulated. The results show that for each LED, different Gauss models should be used. The simulation results are quite satisfying. However, there is a difference between the simulation results and the experimental results. The spectral evaluation indices of fitted both CIE illuminant A and CIE illuminant D65 do not exceed 2.5%. But in experiment, because of the changes of the peak wavelength and the FWHM caused by the current, the spectral evaluation indices of fitted CIE illuminant A and CIE illuminant D65 are around 5%.

We demonstrate the dissipative soliton mode locking in a diode pumped Yb:GdYSiO5(Yb:GYSO) laser operating in the positive dispersion regime. We obtain stable passively mode-locked pulses with strong positive chirp and with very steep spectral edges. The central wavelength is 1050 nm with bandwidth of about 4 nm, autocorrelation trace shown the typical pulse duration is about 3.5 ps. We obtain the maximum average power of 558 mW for a 3.3-W absorbed pump power, with 22% slope efficiency, and a 78-MHz pulse repetition frequency.

We demonstrate a high power continuous-wave (CW) and acoustic-optically (AO) Q-switched 1314-nm laser with a diode-side-pumped Nd:YLF module. A maximum CW output power of 21.6 W is obtained with a diode pump power of 180 W, corresponding to an optical-to-optical conversion efficiency of 12.0% and a slope efficiency of 16.1%. In the Q-switching operation, a highest pulse energy of 3.8 mJ is obtained at a pulse repetition rate of 1 kHz. The shortest pulse width and maximum single peak power are 101.9 ns and 37.3 kW, respectively.

A Q-switched ytterbium-doped fiber laser (YDFL) is proposed and demonstrated using a newly developed multi-walled carbon nanotubes polyethylene oxide (MWCNTs-PEO) film as a passive saturable absorber (SA). The saturable absorber is prepared by mixing the MWCNTs homogeneous solution into a dilute PEO polymer solution before it is left to dry at room temperature to produce thin film. Then the film is sandwiched between two FC/PC fiber connectors and integrated into the laser cavity for Q-switching pulse generation. The laser generates a stable pulse operating at wavelength of 1060.2 nm with a threshold pump power of 53.43 mW. The YDFL generates a stable pulse train with repetition rates ranging from 7.92 to 24.27 kHz by varying 980-nm pump power from 53.42 to 65.72 mW. At 59.55-mW pump power, the lowest pulse width and the highest pulse energy are obtained at 12.18 μs and 143.5 nJ, respectively.

We demonstrate a high power high beam quality diode-pumped 1 112-nm Nd:YAG master-oscillator poweramplifier (MOPA) laser system. To increase the extraction efficiency and output power, a four-pass amplifier scheme is employed. Finally, the injected laser output power is amplified from 26 to 64 W with beam quality factor M2=2.85. Furthermore, a theoretical model that takes the temporal overlap inversion number dynamics into account is employed to analyze the performance of the MOPA laser system, and a good agreement with the experimental data is obtained.

Based on the coupled Ginzburg-Landu equation, we numerically investigate the pulse dynamics in a dispersion-managed normal dispersion Tm-doped mode-locked fiber laser. The influences of the modulation depth and saturation power of saturable absorber on the pulse dynamics are presented. The simulation results show that these parameters are crucial to achieve high pulse energy and high pulse peak power pulsed laser near 2-\mu m wavelength.

We report an experimental study on the synthesis of metal nanoparticles (NPs) with adjustable optical density based on surface plasmon resonance (SPR). Metal NPs prepared by laser ablation in liquid method and the effect of laser parameters on the size, distribution, wavelength of SPR of Ag, Au, and mixture of Ag-Au, and Ag core/Au shell NPs are investigated. Our results show that the adjustable SPR band can be achieved in each class of NPs which is suitable for adjustable optical window applications.

Photodynamic therapy (PDT) has poor therapeutic outcomes for the treatment of port-wine stain (PWS) lesions with long drug-light intervals (DLIs). This letter investigates the possibility of improving the treatment efficacy through increasing the laser power density using a computer simulation and a cock comb model. The computational model includes a Monte Carlo simulation for the laser distribution and a calculation of the singlet oxygen concentrations (1O2). Both simulation and experimental results show that increasing the power density from 100 to 140 mW/cm2 not only improves the PDT efficacy, but also results in the unwanted skin damage.

Laminar optical tomography (LOT) is a new mesoscopic functional optical imaging technique. Currently, the forward problem of LOT image reconstruction is generally solved on the basis of Monte-Carlo (MC) methods. However, considering the nonlinear nature of the image reconstruction in LOT with the increasing number of source positions, methods based on MC take too much computation time. This letter develops a fast image reconstruction algorithm based on perturbation MC (pMC) for reconstructing the absorption or scattering image of a slab medium, which is suitable for LOT or other functional optical tomography system with narrow source-detector separation and dense sampling. To calculate the pMC parameters, i.e., the path length passed by a photon and the collision numbers experienced in each voxel with only one baseline MC simulation, we propose a scheme named as the trajectory translation and target voxel regression (TT&TVR) based on the reciprocity principle. To further speed up the image reconstruction procedure, the weighted average of the pMC parameters for all survival photons is adopted and the region of interest (ROI) is extracted from the raw data to save as the prior information of the image reconstruction. The method is applied to the absorption reconstruction of the layered inhomogeneous media. Results demonstrate that the reconstructing time is less than 20 s with the X-Y section of the sample subdivided into 50 \times 50 voxels, and the target size quantitativeness ratio can be obtained in a satisfying accuracy in the source-detector separations of 0.4 and 1.25 mm, respectively.

Wavelength combining with a transmitting Volume Bragg Grating recorded in photo-thermo-refractive glasses is present. The combining condition is determined with theoretical simulation. The combining efficiency of 81.4% is obtained in the experiment, and it is influenced by the beam quality of the incident beam. The wavefront characteristics of combining beam are improved.

Component object model technology is used to solve problems encountered when using three-dimentional (3D) objects to conduct computer-generated hologram (CGH) fast coding. MATLAB and C/C++ are combined for relevant programming under experimental conditions. The proposed method effectively reduces the time required for holographic encoding of large amounts of 3D object data. The CGHaccelerated computing method based on mixed programming is proven to be highly reliable and practical by testing the 3D data of different data volumes. According to the test results, the proposed method improves the efficiency of holographic encoding. The higher the data volume is, the more significantly the computation speed is improved.

We experimentally investigate the high-order harmonic generation in argon gas cell driven by a multi-cycle broadband infrared laser pulse from a tunable optical-parametric-amplifier (OPA) source. The generation of high-order harmonic continuum with the cut-off photon energy up to 110 eV is observed by tuning the chirp of the 800-nm laser pulse which pumps OPA source. The generation of harmonic continuum is understood in terms of the two-hump structure of the OPA output spectrum and the optimal relative phase of the two humps. The demonstrated scheme is of importance for the generation of extreme ultraviolet (XUV) continuum at higher photon energy region.

A compact static infrared broadband snapshot imaging spectrometer (IBSIS) is presented. It consists of a telescope, three prisms, a focusing lens, and a detector. The first prism disperses sharply in the near-infrared (NIR) range along the vertical direction, and it is relatively non-dispersive in the mid-wave infrared (MWIR) range. The second prism is substantially more dispersive in the MWIR range than in the NIR range along the horizontal direction. The beam deviation caused by the first and second prisms can be controlled by the third prism. The IBSIS yields a two-dimensional dispersion pattern (TDP). The formulas and numerical simulation of the TDP are presented. The methods of target location calculation and spectral signature extraction are described. The IBSIS can locate multiple targets using only one frame of data, which allows for real-time detection and measurement of the energetic targets.

A new spectroscopic method is proposed for the characterization of optical zero-order retarders. It is demonstrated that the retardance as well as the variation of the effective fast axis of a bi-plate zero-order quarter retarder (633 nm) can be obtained with high accuracy in a broadband wavelength range by taking spectra at only three independent angular orientations of the retarder. The calibration results excellently agree with theoretical models, indicating the new method could be used as a simple and reliable way for efficient self-spectral-calibration of optical zero-order retarders.

we report on the generation of cascaded four-wave mixing (CFWM) in a photonic crystal fiber with a high peak power picosecond pulse pumping in the normal dispersion region and a weak continuous wave seeded. We also experimentally investigate the dependence of CFWM bandwidth on the seeding wavelengths. Experimental results demonstrate the existence of optimum seeding wavelengths for broadband CFWM even though the pulse wavelength is 50 nm shorter than the zero dispersion wavelength. And CFWM products spanning more than 300 nm are experimentally obtained.