A novel closed-form expression for average capacity is derived for free-space optical (FSO) links over Gamma-Gamma turbulence channels by considering the effect of misalignment (pointing errors). The simulation results show that the average capacity of the FSO links can be analyzed with the effects of atmospheric turbulence condition, beam width, detector size, jitter variable, and transmitted optical power. Meanwhile, the results are further provided to verify the accuracy of our mathematical analysis. This work is useful for the FSO designer.

Lower tropospheric water vapor measurements are performed at nighttime using the mobile atmosphere monitoring lidar-2 (AML-2) which is operated by the Anhui Institute of Optics and Fine Mechanics. In this lidar system, a 354.7-nm light from a Nd:YAG laser is used as stimulating source, whose Raman shifted center wavelengths are at 386.7 and 407.5 nm for nitrogen and water vapor, respectively. We present a novel and convenient method for determining the Raman lidar calibration constant according to the scanning performance of this lidar. We are likewise able to realize the measurement of water vapor profile in the low troposphere. The error induced by the uncertainty of calibrated constants is within 7% for the Raman lidar system. Experimental results from two months of study indicate that the method of calibrating the lidar system constant is feasible, and the Raman lidar performance is stable and reliable.

The relations between scattering angle (SA) and the degree of polarization (DOP) of skylights are studied. Measurements under different sky conditions demonstrate that all relation curves between SA and DOP can be described as parabolas. DOP reaches its peak when SA is 90° and the sizes of scattering particles are much smaller than the wavelengths of skylight. The peak value of DOP moves by a small drift when the size of the particle increases. We propose and analyze a polarization dependence model for SA and DOP. Results from simulation are in good agreement with experimental results.

An experiment on measuring the magnetic field in Ramsey interaction region of the atomic fountain clock by detecting the Zeeman frequency shift of ⁸⁷Rb hyperfine transition is presented. By mu-metal shielding and coils compensating, the magnetic fluctuations resulting from asymmetry and instability are less than 10 and 0.025 nT, respectively. The relative frequency uncertainty of atomic fountain clock caused by the magnetic field is less than 5.4×10^-16.

The wave packet dynamics of the photodetachment of H^- near dielectric surface are studied by using the wave packet evolution and the autocorrelation function. The results show that the evolutions of the autocorrelation function and the wave packet in the time domain correspond well with each other. Besides, we consider the influence of the electronic state lifetime on the wave packet evolution and the autocorrelation function. Numerical simulation shows that the evolution of the photodetached electronic wave packet near the dielectric surface exhibits some properties similar to the time-resolved two-photon photoemission intensity of surface electron.

Using the effective medium theory and the waveguide eigenvalue equation, we design a multimode planar periodic waveguide. When a plane wave illuminates the grating at the designed angle and wavelength, more than one leaky modes are excited coincidentally. Then the reflection efficiency around this designed angle and wavelength is investigated using a rigorous coupled wave analysis formulation and a gap of reflection peaks is found. Electric field distributions reveal that this high reflectivity gap is due to the coupling between these two coincidentally excited leaky modes.

A novel structure for ultra long span optical transmission systems is proposed. In the scheme, the inverse fast Fourier trans form (IFFT) is used as a way of inverse multiplexing. A 40-Gb/s (total effective capacity) system based on the proposed scheme is simulated to evaluate its performance without consideration for dispersion compensation. Simulation results indicate that the proposed system can tolerate distortion caused by chromatic dispersion effectively after long distance transmission.

Stray light analysis of a three-mirror spatial optical system is presented. The entrance pupil diameter (EPD) of the system is 320 mm, the e?ective focal length (EFL) is 2809 mm, and the field of view (FOV) is 1°×0.5°. Its walls are coated with extinction paint (the absorption coeffcient of which is 97%). The point source transmittance (PST) of the system is thus reduced by up to two orders of magnitude. Moreover, this technique makes it feasible to block the stray light coming from outside of the FOV by increasing the outer baffle length of the system. Adding an inner baffle to both the primary and the secondary mirrors helps not only to block the stray light coming from outside of the FOV but also to decrease the length of the outer baffle. Simulation results show that the PST values are less than 10^-10 when the off-axis angle is larger than 9°. The stray light is also suppressed effectively by placing a glare stop at the first imaging plane of Cassegrain telescope. It is surprising that the PST value is 10^-14 when the off-axis angle is 2° with the placement of glare stop at the first image plane.

Harris corner detector is a classic tool to extract feature. It is stable to illumination change and rotation but unstable to more complicated transform. In order to register images with different viewpoints, we extend Harris corner detector to scale-space to gain invariance to scale change, then we apply affine shape adaptation to the scale invariant point until convergence is reached, giving it invariance to affine transform. With these local features, we use general feature descriptor and matching algorithm to generate matches and then use the matches to calculate the geometric transform matrix, which enables the final registration. Result shows that our algorithm can get more accurate matches than scale invariant feature transform SIFT, and less difference exists between registered images.

A novel personal recognition system utilizing palm vein patterns and a novel technique to analyze these vein patterns is presented. The technique utilizes the curvelet transform to extract features from vein patterns to facilitate recognition. This technique provides optimally sparse representations of objects along the edges. Principal component analysis (PCA) is applied on curvelet-decomposed images for dimensionality reduction. A simple distance-based classifier, such as the nearest-neighbor (NN) classifier, is employed. The experiments are performed using our palm vein database. Experimental results show that the algorithm reaches a recognition accuracy of 99.6% on the database of 500 distinct subjects.

A multi-parameter fusion algorithm (MPFA) for auto-focus (AF) is discussed. The image sharpness evaluation algorithm (ISEA) and zoom tracking method (ZTM) are combined for AF. The zoom motor position (z) and background complexity (c) are regarded as the main parameters of this algorithm. A priority table depending on z and c is proposed. Modified ISEA or ZTM is adopted according to the priority table value. The hardware implementation of the MPFA on Texas Instruments' Davinci digital signal processor is also provided. Results show that the proposed scheme provides faster focusing compared with the conventional approaches.

Light propagation through a metal/nonlinear dielectric material/metal (M-NL-M) structure is numerically studied. The design parameters of the M-NL-M structure are found with the waveguide theory so that the structure only supports the symmetric surface plasmon polaritons (SPP(0)) mode and the antisymmetric surface plasmon polaritons (SPP(1)) mode. The coupling between the two modes within the M-NL-M structure is exploited. Through controlling the propagation constants of the two modes with the intensity-dependent dielectric constant of the nonlinear Kerr material, an effective all-optical control of plasmonic signal modulator can be realized with this M-NL-M structure.

We investigate a theoretical model to accurately predict the output performances of slab laser amplifiers, which is one of the key issues in the study of space-based lasers. The realistic absorbed pump energy density, which induces nonuniformity of stored energy density in the laser medium, is introduced into the model. Using this model, the amplification performances of two space-based laser amplifiers with different pump configurations are compared. The results indicate that the bounce-pumped amplifier (BPA) achieves much higher output energy and efficiency compared with the side-pumped amplifier (SPA); it is also more suitable for space-based lasers.1. F. E. Hovis, J. Edelman, T. Schum, J. Rudd, and K. Andes, Proc. SPIE 6871, 68710E (2008).2. J. Luttmanna, K. Nicklausa, V. Morascha, S. Fua, M. Hofera, M. Trauba, H. D. Hoffmanna, R. Treichelb, C. Wuhrerc, and P. Zellerc, Proc. SPIE 6871, 687109 (2008).3. A. W. Yu, S. X. Li, G. B. Shaw, A. Seas, M. A. Stephen, E. Troupaki, A. Vasilyev, L. Ramos-Izquierdo, A. Lukemier, W. Mamakos, A. Melak, J. Guzek, and A. Rosanova, Proc. SPIE 7193, 719305 (2009).4. F. E. Hovis, N. Martin, and R. Burnham, Proc. SPIE 5798, 101 (2005).5. L. M. Frantz and J. S. Nodvik, J. Appl. Phys. 34, 2346 (1963).6. T. J. Kane, J. M. Eggleston, and R. L. Byer, IEEE J. Quantum Electron. 1, 1195 (1985).7. A. K. Sridharan, S. Saraf, and R. L. Byer, Appl. Opt. 46, 7552 (2007).8. J. M. Eggleston, L. M. Frantz, and H. Injeyan, IEEE J. Quantum Electron. 25, 1855 (1989).9. T. Rutherford, W. M. Tulloch, E. K. Gustafson, and R. L. Byer, IEEE J. Quantum Electron. 36, 205 (2000).

High-power vertical-cavity surface-emitting lasers (VCSELs) are processed using a wet thermal-selective oxidation technique. The VCSEL chips are packaged by employing three different bonding methods of silver solder, In-Sn solder, and metalized diamond heat spreader. After packaging, optical output power, wavelength shift, and thermal resistance of the devices are measured and compared in an experiment. The device packaged with a metalized diamond heat spreader shows the best operation characteristics among the three methods. The 200 \mu m-diameter device bonded with a metalized diamond heat spreader produces a continuous wave optical output power of 0.51 W and a corresponding power density of 1.6 kW/cm² at room temperature. The thermal resistance is as low as 10 K/W. The accelerated aging test is also carried out at high temperature under constant current mode. The device operates for more than 1000 h at 70 ℃, and the total degradation is only about 10%.

The method of fitting damage probability curves of laser-induced damage is introduced to investigate the laser-conditioning mechanism of ZrO2/SiO2 high re°ection (HR) films. The laser-induced damage thresholds (LIDTs) of the sample are tested before and after the laser-conditioning scanning process. The parameters of the defects are obtained through the fitting process of the damage probability curve. It can be concluded that the roles of laser conditioning include two aspects: removing defects with lower threshold and producing new defects with higher threshold. The effect of laser conditioning is dependent on the competition of these two aspects.

A practical method for evaluating the three-dimensional (3D) position and velocity of a moving object used in the parabolic flight experiment is developed by using the binocular stereo vision measurement theory. The camera calibration mathematic model without considering the lens distortion is introduced. The direct linear transformation (DLT) algorithm is improved to accomplish the camera calibration. The camera calibration result and optimization algorithm are used to calculate the object's world coordinate from image coordinate. The 3D position and the velocity of the moving object are obtained. The standard uncertainty in estimating the velocity is 0.0024 m/s, which corresponds to 1% level of the velocity of the object in the experiment. The results show that this method is very useful for the parabolic flight experiments.

AlPO4 mesoporous glass doped with perylene orange (PO) is prepared using two steps. The effects of dipping time and PO concentration on the fluorescent properties and molecular formation are investigated through absorption spectra, excitation spectra, and emission spectra. A slight increase in the intensity of excitation bands formed at 499 and 468 nm is ascribed to PO J-dimers aggregates as the dipping time increased from 2 to 24 h at high PO concentration (4×10^-3 mol/L). This is also the reason behind the concentration increase from 4×10^-6 to 4×10^-3 mol/L for the 16 h dipping. The excitation spectra, and the emission spectra of samples doped with PO show a slight red shift as the dipping time and the PO concentration increase. AlPO4 mesoporous glass is suitable to host the PO at high concentration.

Phase mismatching for third-harmonic generation (THG) in barium metaborate (BBO) crystal is investigated in detail. Upon using BBO crystal in the Type I (oo→e) scheme, in the two independent planes (principal section of the crystal and the plane normal to principal section), when the input second-harmonic beam deviates from the expected direction, phase mismatching occurs and the angle deviation produces different effects on the conversion efficiency. We numerically simulate these two cases of phase mismatching and identify the relation between the conversion efficiency and the deviation angle in the air. The computational results indicate that the phase matching tolerance in the principal section is 0.2° (in the air), while the phase matching tolerance in the plane normal to principal section is 4.5° (in the air). After conducting a lab experiment, the results agree perfectly with the computational results, indicating that the deviation angle in the principal section has a greater effect on the conversion efficiency.

The influence of laser conditioning on defects of HfO2 monolayer films prepared by electron beam evaporation (EBE) is investigated utilizing the spot-size effect of the laser-induced damage. It is found that the laser-induced damage threshold of HfO2 monolayer films can be increased by a factor of 1.3-1.6. It is also found that the defects with low threshold can be removed by laser conditioning and defects with higher threshold may be removed partially.

A TiO2/porous silicon (PS) composite system is prepared by chemical vapor deposition. The crystal form with anatase phase of the samples is evaluated by X-ray diffraction and ultraviolet-visible (UV-vis) absorbance spectra, and the morphology with microsphere of TiO2 particles is characterized by scanning electron microscopy. The composite system formed by this technique gives a broad blue luminescence and the mechanism of photoluminescence with TiO2/PS is also discussed.

High performance optical coating requires excellent uniformity of thin-film. Keeping the surface of evaporation material flat is propitious for the stability of vapor plume, and can improve the uniformity of thin-film. Based on the principle of electron beam spot sweep, a pattern controller in domestic coater is designed. For the purpose of even evaporation during auto-sweep, the influence of the depth of material surface in the crucible on the evaporation characteristic is considered. Pre-melting and evaporation experiments are performed on melting material (Ti3O5), subliming material (SiO2), and semi-melting, semi-subliming material (HfO2). The sweeping experimental results show that using the designed sweep controller can make good performance on evaporation and pre-melting for the above materials.

The optical performance of thin film polarizers is highly sensitive to the layer thicknesses of thin film. The thicknesses of the sensitive layers are optimized in order to gain broader polarizing zone in such case when the total layer thickness does not increase. An automatic layer thickness control system is established, and errors caused by different monitoring methods are analyzed. With this thickness control system, thin-film polarizers with T_p higher than 98% and T_p/T_s higher than 200:1 (T_p and T_s are transmissions for p- and s-polarizations, respectively) with the bandwidth of 11 nm are prepared. Using the system allows for optimum repeatability of three successive runs.

We use the three-dimensional finite-difference time-domain (3D-FDTD) method to model silica tapermicrofiber structures integrated on substrates. The dependence of the transmission on the length of the microfiber is investigated for two different structures. Optimization of the geometric parameters is provided and two substrate materials, namely MgF2 and fluorosilicate glass, are considered. We also investigate the case where the structure is covered with a dielectric material.

A new-style silica planar lightwave circuit (PLC) hybrid integrated triplexer, which can demultiplex 1490-nm download data and 1550-nm download analog signals, as well as transmit 1310-nm upload data, is presented. It combines SiO2 arrayed waveguide gratings (AWGs) with integrated photodetectors (PDs) and a high performance laser diode (LD). The SiO2 AWGs realize the three-wavelength coarse wavelength division multiplexing (CWDM). The crosstalk is less than -40 dB between the 1490- and 1550-nm channels, and less than -45 dB between 1310- and 1490- or 1550-nm channels. For the static performances of the integrated triplexer, its upload output power is 0.4 mW, and the download output photo-generated current is 76 \mu A. In the small-signal measurement, the upstream -3-dB bandwidth of the triplexer is 4 GHz, while the downstream -3-dB bandwidths of both the analog and digital sections reach 1.9 GHz.

A reflection-mode photoacoustic microscope (PAM) for rat brain imaging in vivo is constructed. A pulsed laser is used as an excitation source, and a focused ultrasound transducer is adopted to collect the photoacoustic signal. Raster scanning is applied to acquire three-dimensional (3D) data. The obtained measurements of the lateral and axial resolutions of the microscope are 45 and 15 \mu m, respectively. The imaging depth in the chicken breast tissue is 3.1 mm at a signal-to-noise ratio (SNR) of 20 dB without any signal averaging. The imaging speed is 30 A-line/s. Experimental results in vivo demonstrate the capability of 3D imaging of the brain vessels of the rat after removing the skull.