An ultra-broadband spatially dispersed regenerative amplifier free from spatial chirp

An ultra-broadband Ti:sapphire regenerative amplifier based on spatially dispersed amplification is demonstrated experimentally. Departing from previous reports, a new design of the cavity gets the amplified pulse free from spatial chirp. Utilizing this new regenerative amplifier, chirped pulses with bandwidth (FWHM) of about 80 nm are obtained, and the bandwidth is limited only by that of the incident seed pulses.

自由空间激光远距离传输的地面模拟研究

根据透镜的傅里叶变换性质，提出了采用光学傅里叶变换加级联光学成像放大并结合有限口径接收的方法来实现自由空间激光光束远距离传输的实验室模拟。由此原理设计了自由空间激光远距离传输模拟装置，该装置主要由大口径、长焦距的傅里叶变换平行光管和三级成像放大镜所组成，最大等效传输距离达2.4×10^5km，可用于星间激光通信终端综合通信性能的评估，在设定的误码率下测量终端可能的通信距离，或者在设定的作用通信距离下检测通信的误码率。

Observing the fractional Fourier transform by free-space Fresnel diffraction

The fractional Fourier transform of an object can be observed in the free-space Fresnel diffraction pattern of the object. (C) 1997 Optical Society of America

Relay lens-free birefringence-customized stackable beam-steering modules for optical interconnects

A previously suggested birefringence-customized modular optical interconnect technique is extended for lens-free relay operation. Various lens-free relay imaging models are developed. We claim that the lens-free relay system is important in simplifying an optical interconnect system whenever the imaging conditions permit. To verify the validity of various proposed concepts, we experimentally implemented some 8 x 8 optical permutation modules. High-power efficiency and low channel cross talk were experimentally observed. In general, the larger the channel spacing, the less the cross talk. A quantitative cross-talk measurement of the lens-free relay system shows that, for a fixed channel width of 0.5 mm and channel spacings of 0.5, 1, and 2 mm, a less than -20-dB cross-talk performance can be guaranteed for lens-free relay distances of 40, 280, and 430 mm, respectively. (C) 1998 Optical Society of America.

Corrections to the paraxial approximation of an arbitrary free-propagation beam

A relatively simple transform from an arbitrary solution of the paraxial wave equation to the corresponding exact solution of the Helmholtz wave equation is derived in the condition that the evanescent waves are ignored and is used to study the corrections to the paraxial approximation of an arbitrary free-propagation beam. Specifically, the general lowest-order correction field is given in a very simple form and is proved to be exactly consistent with the perturbation method developed by Lax et nl. [Phys. Rev. A 11, 1365 (1975)]. Some special examples, such as the lowest-order correction to the paraxial approximation of a fundamental Gaussian beam whose waist plane has a parallel shin from the z = 0 plane, are presented. (C) 1998 Optical Society of America.

Double-cladding Yb3+ fiber for free-space optical communication

The experiment result of Nd:YVO4 laser pumped by laser diode that was amplified by double-cladding Yb3+ fiber is reported. Stable mode-locking pulses are obtained at repetition rate of 320 MHz and the output power is 15 mW. When laser power is amplified by Yb3+- doped double-cladding fiber amplifier, its power can get to 600 mW. Based on these, experiment of double-frequency is carried out, and green laser with power of 4 mW is obtained. (c) 2007 Wiley Periodicals, Inc.

Structural and upconversion fluorescence properties of Er3+/Yb3+-codoped lead-free germanium-bismuth glass

We study the structural and infrared-to-visible upconversion fluorescence properties of Er3(+)/Yb3+-codoped lead-free germanium-bismuth glass. The structure of lead-free germanium-bismuth-lanthanum glass is investigated by peak-deconvolution of Raman spectroscopy. Intense green and red emissions centred at 525, 546, and 657nm, corresponding to the transitions H-2(11/2) -> (IT15/2)-I-4 -> S-4(3/2) -> 4I(15/2), and F-4(9/2) -> I-4(15/2), respectively, are observed at room temperature. The quadratic dependence of the 525, 546, and 657nm emissions on excitation power indicates that a two-photon absorption process occurs under 975nm excitation.

Green and red upconversion luminescence in ytterbium-sensitized erbrium-doped novel lead-free germanium bismuth lanthanum glass

Structural and infrared-to-visible upconversion fluorescence properties in ytterbium-sensitized erbrium-doped novel lead-free germanium bismuth-lanthanum glass have been studied. The structure of lead-free germanium-bismuth-lanthanum glass was investigated by peak-deconvolution of Raman spectrum, and the structural information was obtained from the peak wavenumbers. Intense green and red emissions centered at 525, 546, and 657 nm, corresponding to the transitions 2H(11/2) -> I-4(15/2), S-4(3/2) -> I-4(15/2), and F-4(9/2) -> I-4(15/2), respectively, were observed at room temperature. The quadratic dependence of the 525, 546, and 657 nm emissions on excitation power indicates that a two-photon absorption process occurs under 975 nm excitation. This novel lead-free germanium-bismuth-lanthanum glass with low maximum phonon energy (similar to 751 cm(-1)) can be used as potential host material for upconversion lasers. (c) 2005 Published by Elsevier B.V.

Self-adaptive optical systems for long-distance flying optics

The focusing characteristics of long-distance flying optics were studied systemically for TEMmn Gaussian beams. The results show that the ABCD law of parameter q can be extended to Gaussian modes of any order when waist radius w in the imaginary part of parameter q is replaced by Rayleigh range Z(R) of a certain resonator in the equation. The difference between the real focal length and the geometric focal length, defined as Delta f, was calculated for laser applications. A novel self-adaptive optical system was demonstrated for precisely controlling the focusing characteristics of long-distance flying optics, Theoretical analyses and experimental results were consistent. (c) 2006 Optical Society of America.

基于高精度差动干涉仪的微伽重力仪

本文提出的微伽绝对重力仪基于高精度、高稳定的差动干涉仪。详细研究了重力仪的距离测量技术，自由落体运动的距离测量实验表明，本文提出的高精度差动干涉仪可以满足相对不确定度达6.4×10^(-9)的微伽绝对重力仪要求。而且，差动干涉仪比目前广泛应用于绝对重力仪的Mach-Zehnder干涉仪更稳定。