The coherence of a squeezed sodium atom laser generated from a Raman output coupler, in which the sodium atoms in Bose-Einstein condensate (BEC) interact with two light beams consisting of a weaker squeezed coherent probe light and a stronger classical coupling light, is investigated. The results show that in the case of a large mean number of BEC atoms and a weaker probe light field, the atom laser is antibunching, and this atom laser is second-order coherent if the number of BEC atoms in traps is large enough.

The influences of various laser modes on the splitting beam effect of Dammann grating are studied in theory and by numerical simulation. The results show that fundamental mode laser resembles plane wave while high order mode laser differs from plane wave in the splitting beam effect by Dammann grating. Therefore, the fundamental mode laser is more suitable to be the light source to improve the energy efficiency in far-distance image detecting systems, such as laser image ladar, which use Dammann grating in the illumination system.

An internal Brewster guided-mode resonance (GMR) filter is designed. For this kind of GMR filter, the Brewster reflection occurs at the interface of grating/waveguide layers rather than at the interface of air/grating layers. At Brewster angle of 60\circ the GMR filter owns almost 100% reflection at the resonance wavelength of 800 nm with the full-width at half-maximum (FWHM) of 0.2 nm. Its angle response changing with the fabrication deviation is also discussed.

The spatial resolution of conventional distributed fiber optic sensors is 1 m at best, which is inadequate to locate the damage precisely. We adopt an improved sensing technique based on the Brillouin optical time-domain analysis (BOTDA). The stepped pump light is input to stimulate the phonon so that the spatial resolution can be increased to centimeter order and the strain accuracy of 25 micro-strains is obtained. The feasibility of this sensing technique is demonstrated through strain measurement of three concrete box-girders in bending. Experimental results show that the improved BOTDA measurement can provide a comprehensive description on the strain distribution of steel rebar or concrete. Compared with the conventional strain gauges, the improved BOTDA measurement is more stable. By virtue of higher spatial resolution and better measurement accuracy, it has become possible to perform crack detection and localization for concrete structures.

A simple and cost-effective multi-wavelength fiber ring laser based on a chirped Moiré fiber grating (CMFG) and a semiconductor optical amplifier (SOA) is proposed. Stable triple-wavelength lasing oscillations at room temperature are experimentally demonstrated. The measured optical signal-to-noise ratio (SNR) reaches the highest value of 50 dB and the power fluctuation of each wavelength is less than 0.2 dB within a 1-h period. To serve as a wavelength selective element, the CMFG possesses excellent comb-like filtering characteristics including stable wavelength interval and ultra-narrow passband, and its fabrication method is easy and flexible. The lasing oscillation shows a narrower bandwidth than SOA-based multi-wavelength fiber lasers utilizing some other kinds of wavelength selective components. Methods to optimize the laser performance are also discussed.

As a component of near-field scanning optical microscope (NSOM), optical fiber probe is an important factor influncing the equipment resolution. Electroless nickel plating is introduced to metallize the optical fiber probe. The optical fibers are etched by 40% HF with Turner etching method. Through pretreatment, the optical fiber probe is coated with Ni-P film by electroless plating in a constant temperature water tank. Atomic absorption spectrometry (AAS), scanning electron microscopy (SEM), and energy dispersive X-ray spectrometry (EDXS) are carried out to characterize the deposition on fiber probe. We have reproducibly fabricated two kinds of fiber probes with a Ni-P film: aperture probe and apertureless probe. In addition, reductive particle transportation on the surface of fiber probe is proposed to explain the cause of these probes.

The existing local binary pattern (LBP) operators have several disadvantages such as rather long histograms, lower discrimination, and sensitivity to noise. Aiming at these problems, we propose the centralized binary pattern (CBP) operator. CBP operator can significantly reduce the histograms’ dimensionality, offer stronger discrimination, and decrease the white noise’s influence on face images. Moreover, for increasing the recognition accuracy and speed, we use multi-radius CBP histogram as face representation and project it onto locality preserving projection (LPP) space to obtain lower dimensional features. Experiments on FERET and CAS-PEAL databases demonstrate that the proposed method is superior to other modern approaches not only in recognition accuracy but also in recognition speed.

A novel photometric calibration framework is presented for a projector-camera (ProCam) display system, which is currently under booming development. Firstly, a piecewise bilinear model and five 5-ary color coding images are used to construct the homography between the image planes of a projector and a camera. Secondly, a photometric model is proposed to describe the data flow of the ProCam display system for displaying color images on colored surface in a general way. An efficient self-calibration algorithm is correspondingly put forward to recover the model parameters. Aiming to adapt this algorithm to different types of ProCam display system robustly, a 3\times7 masking coupling matrix and a patches image with 1024 color samples are adopted to fit the complex channel interference function of the display system. Finally, the experimental results demonstrate the validity and superiority of this calibration algorithm for the ProCam display system.

Image matting and color transfer are combined to achieve image composition. Firstly, digital matting is used to pull out the region of interest. Secondly, taking color harmonization into account, color transfer techniques are introduced in pasting the region onto the target image. Experimental results show that the proposed approach generates visually pleasing composite images.

The spectral relative phase is directly derived from the spectrally resolved interferogram by the Fourier transform method. Furthermore, the spectral absolute phase can also be found. The spectral absolute phase is used to measure the refractive index. In addition, the group index and the derivatives of the refractive index with respect to the wavelength are given through the polynomial fitting process. The measured results are compared with the published data and the new measurement results of the water are given for the wavelength larger than 1.3 \mum.

In order to improve the characteristics of the general broad-waveguide 808-nm semiconductor laser diode (LD), we design a new type quantum well LD with an asymmetric cladding structure. The structure is grown by metal organic chemical vapor deposition (MOCVD). For the devices with 100-\mum-wide stripe and 1000-\mum-long cavity under continuous-wave (CW) operation condition, the typical threshold current is 190 mA, the slope efficiency is 1.31 W/A, the wall-plug efficiency reaches 63%, and the maximum output power reaches higher than 7 W. And the internal absorption value decreases to 1.5 cm^{-1}.

A diode-pumped Nd:YAG oscillator laser with an end-pumped zigzag slab architecture and weak pump absorption is developed. An output power of 253 W with a slope efficiency of 50.2% and an optical-optical conversion efficiency of 39.6% is achieved from the resonator, which emits the maximum power of 290 W with 840-W pump power. An optimum laser diode (LD) array coolant temperature is chosen in an attempt to realize the weak but uniform pump absorption. Furthermore, we have confirmed that the performance of zigzag slab resonator depends sensitively on the incident angle of the beam at the slab end face.

A high-efficiency Brillouin fiber ring laser is demonstrated using the standard single-mode fiber. The laser exhibits a 3.6-mW threshold. The output power is 22 mW with 40-mW pump power, and the maximum optical-to-optical efficiency is 55%. The output is single wavelength with a 3-dB linewidth of 5 MHz, and the interval of center frequency between the laser and the pump light is 11 GHz (0.088 nm). It is shown that the stimulated Brillouin scattering threshold of ring resonator is lower and the energy transfer efficiency is higher than those in fiber.

The effect of solution temperature and cooling rate on microstructure and mechanical properties of laser solid forming (LSF) Ti-6Al-4V alloy is investigated. The samples are solutions treated at 900, 950, and 1000 C, followed by water quenching, air cooling, and furnace cooling, respectively. It is found that the cooling rate of solution treatment has a more important effect on the microstructure in comparison with the solution temperature. The martensite \alpha’ formed during water quenching results in the higher hardness and tensile strength but lower ductility of samples. With decreasing the cooling rate and increasing the solution temperature, the width of primary \alpha laths increases, and the aspect ratio and volume fraction decrease, which make the hardness and tensile strength decrease and the ductility increase.

Deep ultraviolet lasers have various applications in industries and scientific researches. For 266-nm ultraviolet (UV) laser generation, the good beam quality of 1064-nm laser and the elimination of gray-tracking effect of KTP crystal are two key factors. Using a dynamically stable resonator design, 1064-nm laser with an average power of 52 W is realized with repetition rate of 16 kHz. The measured M2 factor characterizing the beam quality is 1.5. By the elimination of gray-tracking effect of KTP crystal, an 18-W green laser is realized with the M2 factor of 1.6. Using a BBO crystal for the fourth harmonic generation, a 1.9-W 266-nm UV laser is achieved.

Transparent Nd:YAG/YAG composite ceramics are synthesized by solid-state reaction method using high-purity Y2O3, Al2O3, and Nd2O3 powders as raw materials. The mixed powder compacts are sintered at 1780 C for 10 h under vacuum and annealed at 1450 C for 20 h in air. The Nd:YAG/YAG ceramics exhibit a pore free structure with an average grain size of about 30 \mum. The microstructure of the Nd:YAG/YAG composite transparent ceramics is studied and there is no interface between Nd:YAG and YAG ceramics. The Nd ion distribution in one grain is also studied, which shows that there is no segregation of Nd ions as in Nd:YAG crystals.

We demonstrate a quasi-periodic structure exhibiting multiple photonic band gaps (PBGs) based on sub-micron-period poled lithium niobate (LN). The structure consists of two building blocks, each containing a pair of antiparallel poled domains, arranged as a Fibonacci sequence. The gap wavelengths are analyzed with the Fibonacci sequence parameters such as the quasiperiodic indices and the average lattice parameter. The transmission properties are investigated by a traditional 4\times4 matrix method. It has also been proved that the gap depth can be tuned by the lengths of poled domains.

Light dose plays an important role in the non-ablative photorejuvenation based on the theory of selective photothermolysis. However, present techniques for determining the light dose in clinical practice are still not accurate enough. We present a new system which monitors the skin tissue response during the laser irradiation in photorejuvenation by measuring the change of the total attenuation coefficient. We also investigate the relationship between the total attenuation coefficient and the energy density, pulse duration, and pulse repetition. In this procedure, the total attenuation coefficient decreases when the light dose increases and the reduction dependes on the light dose. These experimental results indicate that the new system would be a potential tool for accurate light dose determination.

A modified diffusion approximation model called the hybrid diffusion approximation that can be used for highly absorbing media is investigated. The analytic solution of the hybrid diffusion approximation for reflectance in two-source approximation and steady-state case with extrapolated boundary is obtained. The effects of source approximation on the analytic solution are investigated, and it is validated that two-source approximation in highly absorbing media to describe the optical properties of biological tissue is necessary. Monte Carlo simulation of recovering optical parameters from reflectant data is done with the use of this model. The errors of recovering \mu_{a} and \mu_{s} are smaller than 15% for the reduced albedo between 0.77 and 0.5 with the source-detector separation of 0.4-3 mm.

We experimentally realize a singly resonant optical parameter oscillator (OPO) which operates at the degenerate point of KTiOPO4 (KTP) crystal. A thin film plate polarizer (TFP) is used as the output coupler to obtain linearly polarized 2.12 \mum laser. A maximum output power of 2.2 W at 2.12 \mum is obtained from a near-degenerate, type-II KTP OPO by utilizing a Q-switched diode-pumped Nd:YAG laser operating at 5 kHz.

Electrochemical, thermal, and photophysical properties of novel two- (BPODPA), four- (BBPOPA), and six-branch (TBPOA) triphenylamine chromophores are studied. The decomposition temperature of chromophores reaches 373-412 C. The electrochemical properties is explored by cyclic voltammetry. The ionization potential of chromophores is in the range of 5.14-5.18 eV. Excitation at 400 nm reveals emission peaks at 483-487 nm and the fluorescence quantum yields are 0.73-0.75 in CH2Cl2 Two-photon absorption (TPA) properties of chromophores are measured by nonlinear transmission method. The maximum TPA cross-section values are measured at 758 nm to be 20369 GM (1 GM=10^{-50} cm4s/photon) for TBPOA, 7024 GM for BBPOPA, and 1227 GM for BPODPA, respectively. When pumped with 800-nm laser irradiation, chromophores show strong two-photon excited blue-green fluorescence at 502-518 nm. These results provide a basis for understanding the electronic and optical properties of the conjugated multi-branch chromophore in terms of the underlying molecular and electronic structures.

Visible upconversion emission intensities are investigated in Er3+-doped Y2O3 nanocrystals. We also find that the upconversion intensity varies nonlinearly with the excitation power with a threshold of 110 mW, which indicates that the green and red emissions would be photon avalanche upconversion when the excitation power exceeds the threshold.

The poly(urethane-imide) (PUI) which uses isophorone diisocyanate, dispersed red 19 (DR-19), and pyromellitic dianhydride is synthesized. The PUI is characterized by Fourier transform infrared (FT-IR) spectroscopy, differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The results of DSC and TGA indicate that the PUI exhibits high thermal stability up to its glass-transition temperature of 209 C and 5% heat weight loss temperature of 296 C. The fluorescence spectra of PUI and DR-19 are measured, showing that the fluorescence effect of PUI is very similar to that of DR-19 except for the light decrease of fluorescence intensity, which indicates that the fluorescence effect of PUI is generated by the azobenzene groups in its macromolecular chains. The maximum molar absorption coefficient, absorption wavelength, and chromophores density are measured and used to calculate the third-order nonlinear optical coefficient \chi^{(3)} to be 3.96times10^{-13} esu. The nonlinear refractive index coefficient and molecular hyperpolarizability of PUI are also obtained. PUI is proved to have an excellent optical performance.

An all-optical adder/subtractor (A/S) unit with the help of terahertz optical asymmetric demultiplexer (TOAD) is proposed. The all-optical A/S unit with a set of all-optical full-adders and optical exclusive-ORs (XORs), can be used to perform a fast central processor unit using optical hardware components. We try to exploit the advantages of TOAD-based optical switch to design an integrated all-optical circuit which can perform binary addition and subtraction. With computer simulation results confirming the described methods, conclusions are given.

The free surface and unrotational-symmetric surface optical elements have been applied more and more widely along with the development of optical design technology, although they are still difficult for manufacturing. In this letter, a SiC unrotational-symmetric aspheric surface whose surface equation is z=3\lambda(x3+y3)(\lambda=0.6328 \mum) has been introduced. The tilt abstraction is adopted to minimize the material removal. The surface figures are peak-to-valley (PV) value of 0.327\lambda and root-mean-square (RMS) value of 0.023\lambda. A non-null testing method based on digital mask is proposed to test this surface. The accuracy of the method is testified by the experiment of standard sphere testing.

Atmospheric pressure plasma polishing (APPP) is a precision machining technology used for manufacturing high quality optical surfaces. The changes of surface modulus and hardness after machining prove the distinct improvement of surface mechanical properties. The demonstrated decrease of surface residual stresses testifies the removal of the former deformation layer. And the surface topographies under atomic force microscope (AFM) and scanning electron microscope (SEM) indicate obvious amelioration of the surface status, showing that the 0.926-nm average surface roughness has been achieved.

SO2 monitoring in the flue gas of a coal burning boiler is important for environmental protection. The nonlinearity of practical condition causes deviation from theoretical law. On the basis of the Lambert-Beer Law, a new four-step calibration method is introduced. This method includes cross section interpolation, weighting spectral region combination, acquiring the spectrum with new calibration devices, and least-square fitting. Compared with conventional methods, this new method is low cost, convenient, and accurate. In the proof test, SO2 samples with different concentrations are measured. The average errors are less than 1.5%, while the maximum deviation is less than 4.5%.

Fluorescence analysis applied in the study of lactic acid bacteria (LAB) provides a new method and theory to study probiotics and realize the detection and identification of the strains. It is also possible to achieve automation and computerization. In this letter, the differences between the fluorescence spectra of lactobacillus casei-BDI (Lc-BDI) and Streptococcus thermophilus (St) are shown, and the second-order derivative spectra are used to further study the diversity of these two strains. According to the results, with the excitation wavelengths of 285 and 340 nm, there are significant differences between them. The experiment is repeated for 6 times, showing good repetitiveness.

The laser-induced breakdown spectroscopy is used to analyze the lead content in soils. The analyzed spectral line profile is fitted by Lorentzian function for determining the background and the full-width at half-maximum (FWHM) intensity of spectral line. A self-absorption correction model based on the information of spectral broadening is introduced to calculate the true value of spectral line intensity, which refers to the elemental concentration. The results show that the background intensity obtained by spectral profile fitting is very effective and important due to removing the interference of spectral broadening, and a better precision of calibration analysis is acquired by correcting the self-absorption effect.