Noncollinear-Pumped KTP Optical Parametric Oscillator.

A theoretical analysis and an experimental study are presented on the phase-matching condition of noncollinearly pumped optical parametric oscillators (OPO's) based on a noncritical phase-matching potassium titanyl phosphate (KTP) OPO. It is shown that noncollinearly pumped, double-pass, singly resonant optical parametric oscillators maintain the advantage of round-trip parametric gain in a collinear pump, since in this case the two generated signal waves are coherent, which results in high conversion efficiency and low pump threshold. With this KTP OPO we achieved 31% energy conversion efficiency from a 1064-nm pump wave to 1572-nm eye-safe output. In addition, because the incident pump beam is not perpendicular to the OPO cavity mirrors and consequently no reflected beam flows back into the pump source, we can avoid employing optical isolators.     

数字分量电视图像的光纤传输实验

介绍了光纤传输数字电视的意义，电视信号分量数字化的标准和优点。利用自行研制的２７０Ｍｂ／ｓ光发射机和光接收机，建立了分量数字电视信号的光纤传输系统，直接传输了１００ｋｍ光纤，系统传输无误码，传输后图像质量不变。光接收机灵敏度达－２９．２４ｄＢｍ，动态范围为１３．５ｄＢ。无压缩电视图像的传输对于远程医疗和演播室间转输节目等有非常实际的意义。     

多模光纤温度传感器系统

研制了钴盐溶液热色传感介质光学双波长差分吸收多模光纤温度传感器系统。自制了光纤耦合器件,采用了锁相电路,利用微机直接进行数字锁相探测,信号相除运算和温度校正。该系统实时显示温度,测温范围30℃—50℃,准确度±0.15℃,分辨率0.02℃,在40℃时6小时稳定性±0.05℃,12小时稳定性±0.18℃。主要用于抗电磁干扰的微波辐射治疗和谷物加热干燥等测温应用。     

Aberrations of diffracted wave fields. I. Optical imaging

The concept of aberrations of diffracted waves is revisited by using the Rayleigh-Sommerfeld theory of diffraction, and it is pointed out that these aberrations are in a class by themselves; they are only deceptively similar to the aberrations of a rotationally symmetric imaging system. Although an exact Fourier-transform expression can be written for the diffracted wave field, its numerical calculation is cumbersome because of the dependence of the aberrations of the diffracted wave on the observation point. This is true regardless of whether the diffracted wave field is observed on a plane or a hemisphere. It is shown that the Fresnel and Fraunhofer approximations, which neglect these aberrations and thereby simplify the calculations, are valid in imaging applications.     

Optical absorption in D.C. sputtered InAs films

The absorption coefficient for sputtered InAs films was determined in the region of the absorption edge by the analysis of transmission and reflection spectra. The shape of the absorption edge is discussed assuming that the sample material can be described by a model of microcrystallites immersed in an amorphous matrix. The spectral dependence of the absorption coefficient of amorphous InAs is described using the “non-direct transition” model taking into account the non-parabolicity of the conduction band.     

2.5GHZ光孤子传输

报导了我国首次成功地实现了２．５ＧＨｚ光孤子传输。近变换极限的孤子脉冲源是带有Ｆ－Ｐ标准具的增益开关分布反馈激光二极管。孤子脉冲的功率通过分别由１４８０ｎｍ和９８０ｎｍ泵浦的两个掺饵光纤放大器放大，当入纤功率达到一阶孤子功率时，经过２１ｋｍ色散位移光纤传输后，孤子的输出脉宽保持不变。同时还观察到孤子脉冲压缩现象。     

Nonparaxial gaussian beams: 3. Optical vortices

It is shown that an arbitrary nonparaxial laser vortex near a focal plane in the free space should be represented as a discrete superposition of intrinsic vortices possessing elliptical cross sections. The intrinsic vortices, albeit degenerate with respect to the propagation constants, exhibit a characteristic spectrum of singularities and topological phases.     

Optical interference coatings: eighth topical meeting.

A brief account is given of the Eighth Optical Society of America Topical Meeting on Optical Interference Coatings held 15-20 July 2001 in Banff, Alberta, Canada. Photographs of some attendees are appended.     

Optical implementation of fuzzy-logic controllers. Part II

In part I of a previous study [Appl. Opt. 37, 6937 (1998)] we introduced what is believed to be a novel two-dimensional (2-D) fuzzy-logic optical controller. The complexity of such a setup when we deal with an N-dimensional control procedure leads to a more compact version both in planning demands and in space. Viewing the pros and cons of the 2-D setup, we seek a simpler model and find it in a one- dimensional (1-D) multilayer setup. Here we explain the process of finding the optimal 1-D setup and support the concept with true optical results. The new 1-D optical controller is modular and easy to build, and the results that it yields are quite satisfactory.     

Optical implementation of fuzzy-logic controllers. Part I

In recent years fuzzy-logic-based controllers have become the preferred tool for implementing control mechanisms in high-complexity systems. We suggest novel implementations of a basic fuzzy controller. First, we show the principles of fuzzy-logic control and explain the concept behind the optical controller. Next we review a one-dimensional fuzzy-logic-based optoelectronic controller that was suggested in 1994. Finally, we present a novel two-dimensional optical control approach accompanied by computer simulations of an inverted pendulum. The two-dimensional setup is first given for a dual-input controller and then expanded to a multi-input controller.     

成像光学工程面临的光学问题

文章简单论述了现代成像光学主要领域的情况,指出非球面反射系统是发展的必然趋势。讨论了加工与检验方面的基本情况及应着重深入研究的问题。对镜坯材料也提了一点看法。     

Optical cross-sectional imaging with pulse ultrasound wave assistance.

We have developed an optical cross-sectional imaging method for turbid media with the aid of a pulse ultrasound wave. Observation of deep regions in turbid media, such as tissue samples, is difficult owing to the rapid dispersion of an incoming laser beam by scattering. A pulse ultrasound wave, which is less scattered in tissues, can indicate the measuring point on the basis of the change of the optical scattering properties in a localized region. A depth-resolving capability can be achieved from the time-dependent measurement of the scattered-light intensity as the pulse ultrasound wave propagates in the sample. We verified the method by observing absorptive objects embedded in silicone rubber and by obtaining the cross-sectional image of an absorbing object surrounded by a strong scattering medium.