Analysis of optical systems with extended depth of field using the Wigner distribution function

We describe the use of a Wigner distribution function approach for exploring the problem of extending the depth of field in a hybrid imaging system. The Wigner distribution function, in connection with the phase-space curve that formulates a joint phase-space description of an optical field, is employed as a tool to display and characterize the evolving behavior of the amplitude point spread function as a wave propagating along the optical axis. It provides a comprehensive exhibition of the characteristics for the hybrid imaging system in extending the depth of field from both wave optics and geometrical optics. We use it to analyze several well-known optical designs in extending the depth of field from a new viewpoint. The relationships between this approach and the earlier ambiguity function approach are also briefly investigated. (c) 2006 Optical Society of America.

Study of the transmitter antenna gain for intersatellite laser communications

The gain of a transmitter for intersatellite communications is closely related to the performance of all the links. We calculate the transmitter telescope's gain with the help of the rigorous scalar diffraction theory and equivalent optical layout method. Furthermore, a comparison is performed with the conventional imaging method. The results show that the stop inside the telescope can affect the gain of the telescope. Finally, the gain is calculated under the condition of the aberrations. We find that different aberrations cause different effects. (C) 2006 Society of Photo-Optical Instrumentation Engineers.

Intensity-moments characterization of general pulsed paraxial beams with the Wigner distribution function

On the basis of the space-time Wigner distribution function (STWDF), we use the matrix formalism to study the propagation laws for the intensity moments of quasi-monochromatic and polychromatic pulsed paraxial beams. The advantages of this approach are reviewed. Also, a least-squares fitting method for interpreting the physical meaning of the effective curvature matrix is described by means of the STWDF. Then the concept is extended to the higher-order situation, and what me believe is a novel technique for characterizing the beam phase is presented. (C) 1999 Optical Society of America [S0740-3232(99)001009-1].

变栅距光栅实现啁啾脉冲光谱整形

为了充分利用放大介质的增益带宽，获得脉宽更短，功率更高的输出脉冲，需要将输入到主放大链的种子脉冲进行光谱整形来补偿放大过程中的增益窄化效应。提出了利用变栅距反射光栅实现中心波长1053nm，谱宽6nm啁啾脉冲的光谱整形。运用严格的光栅衍射耦合波理论分析光栅的衍射特性，发现该方案不会引入相位畸变。分别计算和分析了刻槽深度、入射角大小、光栅周期以及入射光波长的变化对衍射效率的影响，通过选取适当的光栅参量可获得0．5％～84％的光谱调制深度。

Gain characteristics of Er3+-doped phosphate glass fibres

An erbium-doped phosphate glass fibre has been drawn by the rod-in-tube technique in our laboratory. The gain for the Er3+-doped phosphate glass fibre with different pump powers and with different input signal wavelengths is investigated. The 2.2-cm-long fibre, pumped by a single-mode 980-nm fibre-pigtailed laser diode, can provide a net gain per unit length greater than 1.8dB/cm. The pump threshold is about 50 mW at the wavelength of 1534 nm, and below 70 mW at 1550 nm. The gain linewidth of the Er3+-doped phosphate glass fibre is greater than 34 nm and can cover the C band in optical communication networks.

Gain and noise figure of a double-pass waveguide amplifier based on Er/Yb-doped phosphate glass

A waveguide amplifier is fabricated by Ag+-Na+ two-step ion exchange on Er/Yb-doped phosphate glass. The spectroscopic performance of glass and the properties of channel waveguide are characterized. A double-pass configuration is adopted to measure the gain and noise figure (NF) of the waveguide amplifier, and the comparison of gain and NF for the single and double-pass configuration of the waveguide amplifier is presented. The results show that the double-pass configuration can make the gain increase from 8.8dB (net gain 2.2dB/cm) of the single-pass one to 14.6 dB (net gain 3.65 dB/cm) for small input power at 1534 nm, and the NF are all lower than 5.5dB for both the configurations.

Visible luminescence in Yb3+-doped gadolinium gallium garnets

In this paper, some results on visible luminescence performed on Yb3+-doped gadolinium gallium garnets under 165 and 940 nm excitation were presented. The upconversion luminescence was ascribed to Yb3+ cooperative luminescence and the presence of rare earth impurity ions. The gain cross-sections of Yb:GGG crystal as a function of excited-state population fraction P were studied. Emission spectra under 165 nm at 20 K showed there was no charge transfer luminescence in Yb:GGG. (c) 2006 Elsevier B.V. All rights reserved.