Based on the Rytov approximation of light propagation in weak turbulent atmosphere, the closed-form expressions of field and average irradiance of each one of the four fundamental families of Helmholtz-Gauss (HzG) beams: cosine-Gauss beams, stationary Mathieu-Gauss beams, stationary parabolic-Gauss beams, and Bessel-Gauss beams, which are propagating in weak turbulent atmosphere, are obtained. The results show that the field and average irradiance can be written as the product of four factors: complex amplitude depending on the z-coordinate only, a Gaussian beam, a factor of complex phase perturbation induced by atmospheric turbulence, and a complex scaled version of the transverse shape of the non-diffracting beam. The effect of weak atmospheric turbulence on irradiance distribution of the HzG beam can be ignored.

The formulas of the quantum electrodynamics have been applied to calculate the spontaneous emission rate of excited atom in dielectric microcavity. The results exhibit damping oscillating patterns which depend sensitively on the scaling parameter and geometrical structure. Compared with the case that the emitting atom is immersed in dielectric, the spontaneous emission rate is depressed obviously and the center or the mean value of the oscillations is intimately related to the real refractive index of the local position where the atom is. In order to explain this phenomenon, we utilize the closed-orbit theory to deal with the classical trajectories of the emitted photon, and extract the corresponding frequencies of the oscillations by Fourier transform. It is found that the oscillations can be represented in terms of the closed-orbits of the photon motion constrained in dielectric microcavity, thus providing another perspective on the spontaneous emission of atom sandwiched by dielectric slabs.

It is demonstrated experimentally that the anharmonic property of the quadrupole trap can be exploited to cool trapped atoms by modulating the trap potential anisotropically. This cooling effect arises from the energy-selective removal of the most energetic trapped atoms and the thermal equilibrium of the remaining atoms. The frequency dependences of the temperature and the fraction of the atoms left in the trap after the modulation are explored. It is also demonstrated that the cooling induced by parametric resonance can also increase the phase space density of the trapped atoms.

Novel polymer distributed feedback (DFB) gratings are fabricated based on photopolymerization to reduce lasing threshold of polymer lasers. A photopolymer formulation sensitive to 355-nm ultraviolet (UV) light is proposed for the fabrication of polymer gratings and it can be used to form polymer films by spin-coating process. A very low surface-relief depth ranging from 12.5 to about 1.0 nm has been demonstrated with a refractive-index modulation of about 0.012. The experimental results indicate that such polymer gratings have promising potentials for the fabrication of low-order DFB organic semiconductor lasers.

Germanium doping in silica can be used as a method for nonlinearity enhancement. Properties of the enhanced nonlinearity in photonic crystal fiber (PCF) with a GeO2-doped core are investigated theoretically by using all-vector finite element method. Numerical result shows that the nonlinear coefficient of PCF is greatly enhanced with increasing doping concentration, furthermore, optimal radius of the doped region should be considered for the desired operating wavelength.

A novel packet format with non-return-to-zero (NRZ) label and duobinary carrier-suppressed return-to-zero (DCS-RZ) payload is proposed for optical packet switching networks. NRZ label is followed by DCS-RZ payload with a certain guard time. The spectra of the low-rate NRZ label locate around the optical carrier frequency where some parts of the corresponding spectra of the high-rate DCS-RZ payload have been suppressed due to DCS-RZ modulation. At the switching node, the label or payload extraction can be realized simply through an optical bandpass or notch filter respectively. The feasibility of the scheme is verified by the simulation on the famous photonic design platform designed by Virtual Photonics Inc. (VPI). The effects of optical filter bandwidth on the received signal quality are discussed by analyzing bit error rate (BER) and contrast ratio performances.

An effective method for reducing the speckle noise in digital holography is proposed in this paper. Different from the methods based on classical filtering technique, it utilizes the multiple holograms which are generated by rotating the illuminating light continuously. The intensity images reconstructed by a series of holograms generated by rotating the illuminating light possess different speckle patterns. Hence by properly averaging the reconstructed intensity fields, the speckle noises can be reduced greatly. Experimental results show that the proposed method is simple and effective to reduce speckle noise in digital holography.

A novel image fusion algorithm based on wavelet-based contourlet transform (WBCT) and principal component analysis (PCA) is proposed. The PCA method is adopted for the low-frequency components. Using the proposed algorithm to choose the greater of the active measures, the region consistency test is performed for the high-frequency components. Experiments show that the proposed method works better in preserving the edge and texture information than wavelet transform method and Laplacian pyramid (LP) method do in image fusion. Four indicators for the fusion image are given to compare the proposed method with other methods.

SiO2-TiO2 sol-gel films are deposited on SiO2/Si by dip-coating technique. The SiO2-TiO2 strips are fabricated by laser direct writing using an ytterbium fiber laser and followed by chemical etching. Surface structures, morphologies and roughness of the films and strips are characterized. The experimental results demonstrate that the SiO2-TiO2 sol-gel film is loose in structure and a shrinkage concave groove forms if the film is irradiated by laser beam. The surface roughness of both non-irradiated and laser irradiated areas increases with the chemical etching time. But the roughness of laser irradiated area increases more than that of non-irradiated area under the same etching time. After being etched for 28 s, the surface roughness value of the laser irradiated area increases from 0.3 nm to 3.1 nm.

We propose a two-color scheme of atom waveguides and one-dimensional (1D) optical lattices using evanescent wave fields of different transverse modes around an optical micro/nano-fiber. The atom guide potential can be produced when the optical fiber carries a red-detuned light with TE01 mode and a blue-detuned light with HE11 mode, and the 1D optical lattice potential can be produced when the red-detuned light is transformed to the superposition of the TE01 mode and HE11 mode. The two trapping potentials can be transformed to each other for accurately controlling mode transformation for the red-detuned light. This might provide a new approach to realize flexible transition between the guiding and trapping states of atoms.

The fatigue properties of laser peened aluminum alloy 7050 specimens with fastener holes were investigated. The surface profile and residual stress induced in the shock affected zone were characterized. Then, the fatigue specimens with notch were treated by laser peening (LP), and the fatigue lifes of LP-treated specimens were measured and compared with base materials without LP. The results indicated that LP improved the fatigue lifes of all tested specimens. The average fatigue lifes of specimens treated by LP before hole-drilling were 173% longer than those of untreated samples and had better effects than those specimens treated by LP after hole-drilling.

Dynamics of a semiconductor laser subject to moderate optical feedback operating in the low-frequency fluctuation regime is numerically investigated. Multimode Lang-Kobayashi (LK) equations show that the low-frequency intensity dropout including the total intensity and sub-modes intensity is accompanied by sudden dropout simultaneously, which is in good agreement with experimental observation. The power fluctuation is quite annoying in practical applications, therefore it becomes important to study the mechanism of power fluctuation. It is also shown that many factors, such as spontaneous emission noise and feedback parameter, may influence power fluctuation larger than previously expected.

We demonstrated the highly efficient continuous wave (CW) and Q-switched infrared laser from a diode-side-pumped Nd:YAG crystal. A CW output as high as 66 W at 1319 nm was achieved under the pump power of 460 W, corresponding to a coversion efficiency of 14.3%. A maximum average power of 8.9 W of TEM00 mode was obtained in Q-switched operation at the repetition rate of 8 kHz. The performance of the laser considering the thermal lens effect induced by pump power was also analyzed.

A high-repetition-rate eye-safe optical parametric oscillator (OPO), using a non-critically phase-matched KTP crystal intracavity pumped by a passively Q-switched Nd:GdVO4/Cr4+:YAG laser, is experimentally demonstrated. The conversion efficiency for the average power is 7% from pump diode input to OPO signal output and the slope efficiency is up to 10.3%. With an incident pump power of 7.3 W, the compact intracavity OPO (IOPO) cavity, operating at 15 kHz, produces an average power of 0.57 W at 1570 nm with a pulse width as short as 6 ns. The peak power at 1570 nm is higher than 6.3 kW.

The transmission properties of one-dimensional photonic crystals containing double-negative and single-negative materials are studied theoretically. A special kind of photonic band gap is found in this structure. This gap is invariant with scaling and insensitive to thickness fluctuation. But when changing the ratio of the thickness of two media, the width of the gap could be enlarged. The defect modes are analyzed by inducing a linear defect layer in the structure. It is found that the number of defect modes will increase when the thickness of the defect layer becomes larger.

Ytterbium-doped yttrium oxysulfide (Yb:Y2O2S) has been synthesized by solid-state reaction with sulfide flux. Diffuse reflection and emission spectra have been measured in order to determine the crystal field splitting of Yb3+ ion in the YOS lattice. According to the crystal-field levels probed in the spectra, the crystal field splitting of 2G7/2 manifold of Yb3+ ion in YOS is 709 cm-1, which is large enough for the quasi-three-level laser operation of Yb3+ ion. Emission peak position, width, full-width at half maximum (FWHM), and normalized intensity of Yb:YOS are fitted from its emission spectrum. For comparison, relevant data of 5.4 at.-% Yb:YAG is also provided.

Nonlinear optical properties of stimulated Brillouin scattering (SBS) to signal detection in water are analyzed. With the threshold characteristics, SBS only occurs when the high power laser is focused in the SBS cell. When there is an object present in front of the focus, it leads to lower incident intensity and then SBS does not occur. The backward SBS signal depends on the focusing location. The nonlinear optical properties of SBS process in the focusing regime are analyzed theoretically. With the object coming near to the focusing center, the backward Stokes signal rises up from zero to a maximum, and then grows to saturation. The delay time of the echo signal to pump signal can give the object location. In experiment, the peak position of varying rate of energy can give object location.

We experimentally demonstrate amplitude squeezed soliton utilizing intensity-dependent self-phase modulation in an asymmetric Sagnac interferometer. The system, whose components are connected via ferrule connector/physical connection (FC/PC) fiber connectors, constitutes all-fiber configuration to generate squeezed soliton. Soliton amplitude reduction measured by homodyne detection is near 4.0 dB below the shot-noise level. Optimal squeezing fields in both simple and compact all-fiber configuration are obtained.

By the 90 deg. elastic light scattering investigation and far field observation in the range of 20-800 centigrade, the relation between behavior of light scattering anomalies and evolution of nanodomain structures in lattice of barium sodium niobate (Ba2NaNb5O15, BSN) crystal was clarified. The correlation between anomalies on the temperature curves of the elastic light scattering intensity and temperature transformations of nanodomains was studied by X-ray and electron microscope methods. Phase transition near 500 centigrade and movement in field of scattering light could be explained by appearance of a new incommensurate phase.

A novel lens system with correction of secondary spectrum without using anomalous glasses is presented. The lens system comprises four separated lens components, with three of them being subapertures. Two examples of apochromatic telescope are presented, both with the use of typical normal glasses, namely crown K9 and flint F5 glasses, and low-cost slightly anomalous dispersion glasses. Secondary spectrum and other chromatic aberrations of the two design examples are corrected.

This work has demonstrated that with silver superlens, the resolution of conventional optical lithography can be improved significantly. Experimental and simulative results are given to verify the facts that the resolution and the pattern fidelity are sensitive to the contact tightness between layers.

Enhancement of light extraction in a GaInN light-emitting diode (LED) employing an omni-directional reflector (ODR) consisting of GaN, SnO2 nanorod and an Ag layer was presented. The ODR comprises a transparent, quarterwave layer of SnO2 nanorod claded by silver and serves as an ohmic contact to p-type GaN. Transparent SnO2 sols were obtained by sol-gel method from SnCl 2H2O, and SnO2 thin films were prepared by dip-coating technique. The average size of the spherical SnO2 particles obtained is 200 nm. The refractive index of the nanorod SnO2 film layer is 2.01. The GaInN LEDs with GaN/SnO2/Ag ODR show a lower forward voltage. This was attributed to the enhanced reflectivity of the ODR that employs the nanorod SnO2 film layer. Experimental results show that ODR-LEDs have lower optical losses and higher extraction efficiency as compared to conventional LEDs with Ni/Au contacts and conventional LEDs employing a distributed Bragg reflector (DBR).

The fluorescent spectrum and the excitation spectrum were used to present the cluster molecular structure feature in ethanol-water solutions. Through analyzing the fluorescent characteristics of an excimer, it is proposed that the excimers are formed between the ethanol-water cluster molecules in the excited state and in the ground state. The fluorescent lifetime and the fluorescent intensity decay process give information about the photo-physical and photo-chemical processes of the formation and the dissociation of an excimer. The theoretical calculation and physical analysis coincide with the experimental results. The preliminary conclusion about the structure feature of ethanol-water cluster molecule is that it has a planar one like a sandwich.