Quantum billiards have attracted much interest in many fields. People have made a lot of researches on the two-dimensional (2D) billiard systems. Contrary to the 2D billiard, due to the complication of its classical periodic orbits, no one has studied the correspondence between the quantum spectra and the classical orbits of the three-dimensional (3D) billiards. Taking the cubic billiard as an example, using the periodic orbit theory, we find the periodic orbit of the cubic billiard and study the correspondence between the quantum spectra and the length of the classical orbits in 3D system. The Fourier transformed spectrum of this system has allowed direct comparison between peaks in such plot and the length of the periodic orbits, which verifies the correctness of the periodic orbit theory. This is another example showing that semiclassical method provides a bridge between quantum and classical mechanics.

There are two general methods in radiometric calibration of detectors, one is based on radiation sources and the other based on detectors. Because the two methods need to establish a primary standard of high precision and a transfer chain, precision of the standard will be reduced by extension of the chain. A new calibration method of detectors can be realized by using correlated photons generated in spontaneous parametric down-conversion (SPDC) effect of nonlinear crystal, without needing transfer chain. Using 351.1-nm output of a tunable laser to pump 'beta'-barium borate (BBO) crystal, an absolute calibration experimental system of single photon detectors based on correlated photons is performed. The quantum efficiency of photomultiplier (PMT) at 702.2 nm is measured by the setup. Advantages of this method over traditional methods are also pointed out by comparison.

By using the amplified 10-GHz, 5.5-ps sech2 pulses with high quality and chirp-free from regeneratively mode-locked fiber laser (RMLFL) as the soliton source, 2-5 order optical soliton phenomena are observed successfully in a 4.28-km dispersion flattened fiber. The experimental results agree well with the theoretical calculation.

A new method of absolute phase evaluation for three-dimensional (3D) profile measurement using fringe projection is presented, which combines the gray code and the phase shift technique. Two kinds of fringe patterns are projected onto the object surface respectively, one is sinusoidal intensity distribution used for phase demodulation and the other is gray code fringe pattern for unwrapping. These images are acquired by camera and stored into computer. The absolute phase is obtained by analyzing these images. The validity of this method is verified experimentally. The method is superior to other phase unwrapping methods.

To meet the design and usage requirements of the precision light beam scanner, the thermoelastic distortion of prism is detailedly analyzed by the thermal-structure coupling method, the influence of which, on the surface deformations of prism, is conclusively proved far greater than that of only the gravity load without temperature fluctuation. With the temperature fluctuation from 20 to 20.5 Celsius degrees, the strains as well as the stresses appropriately eightfold increase, which right accords with the actual results measured by Zygo Mark interferometer with the error of not over 10%. Therefore some strict temperature-controlled measures are necessary for the scanner.

A diode-end-pumped electro-optic (EO) Q-switched Nd:YVO4 laser operating at repetition rate of 10 kpps (pulses per second) was reported. A block of La3Ga5SiO14 (LGS) single crystal was used as a Q-switch and the driver was a metal oxide semiconductor field effect transistor (MOS-FET) pulser of high repetition rate and high voltage. At continuous wave (CW) operation, the slope efficiency of the laser was 46%, and maximum optical-to-optical efficiency was 38.5%. Using an output coupler with transmission of 70%, a 10-kpps Q-switched pulse train with 0.4-mJ monopulse energy and 8.2-ns pulse width was achieved, the optical conversion efficiency was around 15%, and the beam quality M2 factor was less than 1.2.

A passively Q-switched Nd^(3+):YAG laser with corner cube is theoretically and experimentally studied. We analyze the polarization variation in cavity and simulate the peak power, pulse energy and pulse width changed with the rotation angle of corner cube numerically. An experiment is made to verify the theoretical results. With rotating the angle of corner cube about the axis the variation range of peak power is 1.77 MW (from 10.36 to 8.59 MW), and that of pulse energy is 14.9 mJ (from 159.5 to 174.4 mJ), the fluctuation of pulse width is 2.95 ns. The experimental results agree with the theoretical analysis to the extent of variation rules. The most dynamic to static energy ratio of 62.5% is achieved.

Ultrashort pulses were generated in passively mode-locked Nd:YAG and Nd:GdVO4 lasers pumped by a pulsed laser diode with 10-Hz repetition rate. Stable mode-locked pulse trains were produced with the pulse width of 10 ps. The evolution of the mode-locked pulse was observed in the experiment and was discussed in detail. Comparing the pulse evolutions of Nd:YAG and Nd:GdVO4 lasers, we found that the buildup time of the steady-state mode-locking with semiconductor saturable absorber mirrors (SESAMs) was relevant to the upper-state lifetime and the emission cross-section of the gain medium.

A couple of simple-structure phase modulators were used in active mode-locked fiber laser to implement repetition rate continuous tuning. The laser produces pulse as short as 5.7 ps whose repetition rate tuning can cover the spacing of the adjoining order mode-locking frequencies.

A wavelength tunable, high repetition rate mode-locked fiber ring laser was demonstrated. In the experiment, photonic crystal fiber (PCF) is used as an intracavity compression medium. The high nonlinearity and anomalous dispersion of PCF can cause intracavity compression and result in significant reduction in the pulse width. The pulses duration at the repetition rate of 9.99 GHz was less than 10 ps over the range of 1532-1565 nm.

Energy storage and heat deposition in Cr,Yb,Er co-doped phosphate glass were reported. A model based on rate equations was used to determine the energy storage from the free-oscillating output energy characteristics. The heat deposition was calculated by measuring the temperature rise of the glass rod. The results provided important information for the glass operating in Q-switched mode, and also for calculating the temperature profiles and cooling requirements of the glass under single shot and repetitive pulsed conditions.

Steady state and time-resolved autofluorescence spectroscopies are employed to study the autofluorescence characteristics of human colonic tissues in vitro. The excitation wavelength varies from 260 to 540 nm, and the corresponding fluorescence emission spectra are acquired from 280 to 800 nm. Significant difference in fluorescence intensity of excitation-emission matrices (EEMs) is observed between normal and tumor colonic tissues. Compared with normal colonic tissue, low nicotinamide adenine dinucleotide (phosphate) (NAD(P)H) and flavin adenine dinucleotide (FAD), and high amino acids and protoporphyrin IX (PpIX) fluorescences characterize high-grade malignant tissue. Moreover, the autofluorescence lifetimes of normal and carcinomatous colonic tissues at 635 nm under 397-nm excitation are about 4.32+-0.12 and 18.45+-0.05 ns, respectively. The high accumulation of endogenous PpIX in colonic cancers is demonstrated in both steady state and time-resolved autofluorescence spectroscopies.

A novel InGaAs/InAlAs coupled quantum well structure is proposed for large field-induced refractive index change with low absorption loss. In the case of low applied electric field of 15 kV/cm and low absorption loss ('alpha' <= 100 cm^(-1)), a large field-induced refractive index change (for transverse electric (TE) mode, 'Delta' n = 0.012; for transverse magnetic (TM) mode, 'Delta' n = 0.0126) is obtained in the structure at the operation wavelength of 1.55 um. The value is larger by over one order of magnitude than that in a rectangular quantum well. The result is very attractive for semiconductor optical switching devices.

Light extraction efficiency of organic light emitting diode (OLED) based on various photonic crystal slab (PCS) structures was studied. By using the finite-difference time-domain (FDTD) method, we investigated the effect of several parameters, including filling factor and lattice constant, on the enhancement of light extraction efficiency of three basic PCSs, and got the most effective one. Two novel designs of "interlaced" and "double-interlaced" PCS structures based on the most effective basic PCS structure were introduced, and the "interlaced" one was proved to be even more efficient than its prototype. Large enhancement of light extraction efficiency resulted from the coupling to leaky modes in the expended light cone of a band structure, the diffraction in the space between columns, as well as the strong scattering at indium-tin-oxide/glass interfaces.

The hybrid sensitizer rhodamine B and coumarin or eosin and coumarin is used to sensitize nanocrystalline porous films. Absorption of the nanocrystalline photovoltaic cell (NPC) is improved in visible light. The performance of these cells is more effective than that of cells sensitized only by sensitizer rhodamine B or eosin. In the simulative solar light, cell sensitized by hybrid sensitizer rhodamine B and coumarin can get open circuit voltage (Voc) of 550 mV and short circuit current (Isc) of 0.1375 mA/cm2.

Differential absorption lidar (DIAL) has been successfully used to detect vapor material, however limited to detect single vapor using two closely spaced wavelengths. The progress in multiple-wavelength lasers motivates the need for detection and estimation algorithms that have the capability for simultaneous detection of multiple materials. In this paper, a simple and accurate algorithm is presented for simultaneously detecting and estimating multiple vapor materials with multiple-wavelength DIAL, which based on the maximum likelihood estimation (MLE) methodology. The performance of the algorithm is evaluated by simulation experiments, the results show that this algorithm can separately identify and quantify vapor material in mixtures and perform quite well.

Tunable diode laser absorption spectroscopy (TDLAS) is a powerful technique to measure trace gas, which can provide high sensitivity, high selectivity, and fast time response. A brief description of our instruments with room-temperature near infrared tunable diode laser designed to measure greenhouse gas (i.e., CH4, CO2) in the ambient air is presented. A multiple-reflection cell and the second harmonic detection technique are used to lower the detection limit. The detection limit of the instrument is below 100 ppbv for CH4 and 10 ppmv for CO2, which is enough to the measurements of ambient CH4 and CO2. The instruments have been used to monitor the methane and carbon dioxide of the ambient air in a long time in Fengtai, Beijing. The results of measurement are shown and discussed in this paper.

A series of thin Ag films with different thicknesses grown under identical conditions are analyzed by means of spectrophotometer. From these measurements the values of refractive index and extinction coefficient are calculated. The films are deposited onto BK7 glass substrates by direct current (DC) magnetron sputtering. It is found that the optical properties of the Ag films can be affected by films thickness. Below critical thickness of 17 nm, which is the thickness at which Ag films form continuous films, the optical properties and constants vary significantly with thickness increasing and then tend to a stable value up to about 40 nm. At the same time, X-ray diffraction measurement is carried out to examine the microstructure evolution of Ag films as a function of films thickness. The relation between optical properties and microstructure is discussed.

The ultrafast nonlinear optical response of Ag:BaTiO3 composite films synthesized by pulse laser deposition (PLD) is studied at the near-ultraviolet (400 nm) wavelength. The pulse duration of the laser used in the measurement is 200 fs. The real and imaginary parts of the third-order nonlinear susceptibility 'chi'(3) of the composite materials are measured. The composite films indicate self-focusing effect and nonlinear saturation, the values of Re'chi'(3) and Im'chi'(3) are measured to be 3.42*10^(-10) and -1.37*10^(-10) esu respectively, which are much lower than those reported before. It is mainly because that the duration of the laser used in the measurements is too short to induce the hot electron excitation and the thermal effect. The ultrafast nonlinear saturated absorption response of the Ag:BaTiO3 composite films may have potential applications for femtosecond laser mode locking.