This paper investigated the voltage-dependent birefringence and absorption coefficient of liquid crystals BL-009 with the incident light of 560 nm. The voltage dependences of birefringence and absorption coefficient were given.

For a pulse under the same stretch ratio there are two cases: one is the incident angle being less than Littrow angle and the other is the incident angle being bigger than Littrow angle. Investigation shows that the needed grating width is less in the former case than that in the latter case, and with the incident angle being one optimum value the needed grating width will reach the maximum in first case. Under the same condition the perpendicular distance between the gratings is also much less in first case than that in second case.

Two simple techniques for the compensation of the temperature effects in fiber Bragg gratings (FBGs) tuned by magnetostrictive transducers are demonstrated. The Bragg wavelengths were tuned by the magnetic field through the magnetostrictive transducer and two FBG′s are arranged in such a way that the magnetostrictive effects on the two gratings are added together, while the temperature effects are cancelled out. Using these techniques, it has been able to reduce the temperature sensitivity of the sensor by more than 10 times, the additional wavelength shift due to the temperature was only 0 11 nm within the range of 22℃～80℃.

In consideration of bare optical fiber being fragility, the steel capillary encapsulating technique for FBG sensor was developed in this study, and then the temperature and strain sensing properties of the encapsulated FBG sensor were experimentally studied on material test system and under hot water, respectively. The comparison of the experimental results between encapsulated fiber and bare fiber indicated that the strain sensing properties of the encapsulated FBG sensor are nearly the same as that of bare FBG, however, the temperature sensing ability of encapsulated FBG sensor is improved and the sensitivity coefficient is 2.5 times as much as that of bare FBG. The strain and temperature sensing precisions of the encapsulated FBG are 1 με and 0.05℃, respectively. The encapsulated FBG is proper for application in civil engineering.

The principle of all-optical switching in fiber Bragg grating (FBG) is illustrated. Yb-doped phase-shifted FBG is adopted to decrease the need for the power of pump from the aspects of structure and material. The transmittivity of phase-shifted FBG is computed using the method of transfer matrix. The result shows the availability of decreasing the power of pump by using the phase-shifted FBG. The extinction ratios are computed under different pump powers. Theoretically, low power all-optical switching in phase-shifted FBG is promising.

Considering the laser applications in biology and medicine as background, this paper presented a theoretical research on the hyperbolic heat conduction in laser irradiated tissue. A numerical model was established by combining the seven-flux model of light propagation with the two-dimensional hyperbolic heat conduction model in cylindrical coordinates. It showed that there exists a great discrepancy between the results obtained by treating the laser irradiation as volumetric absorption (i.e. taking laser scattering and absorption into consideration) and those obtained by treating the laser irradiation as the second boundary condition. The effects of the scattering and absorption coefficients of tissue on the hyperbolic heat conduction in laser irradiated tissue were discussed.

Because the ideal condition which quantization error has a white power spectrum is never valid on the state of multilevel quantization, the intrinsic low frequency characteristic of image is inflected by the processing of error diffusion only dealed with highpass filter (error blue shift). In this paper, it is proposed that the ideal error filter of error diffusion alogrithm should have greater gains on the high frequency, and finite attenuation on the low frequency. Accoding to such idea, the impulse response of error filter is designed anew, and the stability of filter is taken into account. With the filter the optimized algorithm of multilevel error diffusion used for color image quantization is formed.

This paper discusses a new method for blurring images restoration. The blurring factor is not necessary to be known in advanced to restore these images. This algorithm is easy to be programmed and has a popular capability. The computer algorithm is analyzed in this paper and the result is given at the end.

In this paper, the laser feedback interference phenomenon is analyzed and discussed. The basic interference theory and signal processing technique are studied; some typical sensing applications are introduced. Laser feedback interference is different from other convertional interference. The optical feedback interference of semiconductor laser has many advantages in that optical system is much simple and is easily aligned; additional optical elements are not required. A compact sensor was constructed for the online measurement of the distance, displacement and velocity. It is a promising technique used in microelectromechanical systems (MEMS), optical engineering and other engineering application.

An efficient green laser has been realized by external frequency doubling of a LD-pumped single-frequency ring cw Nd∶YVO_4 laser in PPKTP resonator. The maximum green power is 76 mW at IR input power of 150 mW, resulting in the conversion efficiency of 50.6%.

The factors which influence the ultimate output power of semiconductor laser are analyzed. The aluminum-free two-quantum-well semiconductor laser which wavelength is 940 nm is made by MOCVD. As a result, the peak wavelength of the aluminum-free two-quantum-well semiconductor laser is 940 2 nm, the full-width-half-maximum (FWHM) is 2 nm, the continuous output power is 10 W, and the incremental efficiency is 1 09 W/A.

The absorption spectra of spirobenzopyran 6-nitroBIPS doped polystyrene thin film with and without UV irradiation were measured. All-optical modulation of 590 nm probe light utilizing the alteration of the absorption of the thin film was studied. The dependence of the optical modulation on the concentration of the dye doped and the intensity of the excitation UV light was also studied. The photochemical quantum yield is 0.24 and the molar absorption coefficient at 590 nm of the photoproduct is 2.0×10 4 Lmol -1 cm -1 according to the theoretical fitting. The time constants of the front line and the after-edge of the modulated light signal were about 131 ns and 18 μs, respectively.

Amorphous boron nitride thin film was prepared on the titanium coated ceramic substrate by pulsed laser deposition technique (PLD). The microstructure of the film was examined by using X-ray diffraction, scanning electron microscopy and Raman spectroscopy. The electron field emission characteristics were investigated. The turn-on field was 4.6 V/μm. The current density was 50 μA/cm 2 at an electric field of 9 V/μm.

The 180 degree back scattering character of biologic tissue and other turbid mediae can reflect the media′s information inside. Regarding turbid media as a "Black-box", the back scattering characteristic parameters for linear-polarized light in trubid media can be expressed by a polarization plane rotation angle α, polarization maintaining factor β and reflectivity r. A schematic of the measurement about the characteristic parameter was designed. And the milk′s deionized water solutions with different concentration were measured. When the concentration is 25%, α=3°, β=0 15, r=0 09. When the solution′s concentration is changed, the three parameters will be changed, too.

A laser-diode based optical system which can measure aerosol particle size and concentration is described in this paper. The light scattering response characteristics of the system are calculated based on Mie light scattering theory. Some experimental results show that the system has high counting accuracy, efficiency and reproducibility, and suitable for verification of cleanliness class and measurement of ambient aerosol size distribution.

Based on the analysis and calculation of attenuation of the light-blocked attenuator in theory and experiment, it is found that the total attenuation should include light-blocked-only attenuation and mode-mismatched attenuation and their relationship.

A numerical method for the point defect impact in transmission fibers on back-pumped fiber Raman amplifiers (B-DFRAs) is derived, accounting to both loss and reflection effects. Characteristics of gain, amplified spontaneous Raman scattering and double Rayleigh backscattering in a B-DFRA with point defect are studied separately, and the comprehensive effect of the point defect is discussed by equivalent receiver sensitivity.

This paper analyzes and compares several PMD measurement methods based on the characteristics of passive optical components for both single-stage optical isolator and dual-stage optical isolator. It is shown that the Jones Matrix Eigenanalysis method is suitable.