双光栅调谐窄带染料激光器

染料激光器使用双光栅调谐方法,装置十分简单,腔长可以做得很短,容易获得单模(纵模)输出,受到人们的重视.根据工作的需要,我们采用上海光学仪器厂生产的光栅,研制了这种双光栅调谐的N_2泵浦染料激光器.实验所用光路如图1所示.N_2激光器输出为100千瓦,脉宽约10毫微秒,器件长期运转表明,工作性能较稳定.聚焦透镜L用球面镜与柱面镜组合,等效焦距为8厘米.染料用国产商品若丹明6G,浓度为2.5×10~(-3)克分子/升.M为镀铝反射镜,G_1、G_2均采用上海光学仪器厂生产的闪耀光栅.`腔长为24厘米.     

一种优化的宽带聚焦波束形成算法

提出了一种基于最佳聚焦频率的旋转信号子空间法来实现宽带信号波束形成.通过确定最佳聚焦频率,使宽带信号的各个子带通过聚焦矩阵都聚焦在最佳聚焦频率上,然后用常规延迟求和波束形成算法完成恒定束宽波束形成.仿真结果表明,在宽带情况下,阵列输出的主波束宽度,旁瓣级和波束指向均能保持恒定.     

高功率激光加工中光束聚焦的分析和模拟

在高功率激光加工应用中,不同的加工形式对激光光束的聚焦性能要求不同,因而采取的聚焦方式也不一样.研究介绍了高功率激光加工中激光光束聚焦的几种常用方式,包括透镜聚焦、球面镜反射聚焦和离轴抛物面镜反射聚焦.系统地分析了这几种聚焦方式各自的优缺点及其应用领域,并且对这几种聚焦方式进行了模拟分析,形象、直观地反映出各种聚焦方式的聚焦效果.     

基于矢量阵宽带MVDR聚焦波束形成的水下噪声源定位方法

该文研究了可应用于水下噪声源近场定位的矢量阵宽带MVDR聚焦波束形成方法,其中包括基于子频带分解的矢最阵非相干宽带聚焦波束形成(ISMMVDR-VFB)以及矢量阵相干宽带CSS-MVDR聚焦波束形成(CSSMVDR-VFB).两种方法将宽带MVDR高分辨方位估计方法及矢量阵信号处理技术与聚焦波束形成相融合,较常规聚焦波束形成具有更高的分辨力和更低的旁瓣级,能解决"左右舷模糊"问题并提高处理增益.与非相干算法ISMMVDR-VFB相比,CSSMVDR-VFB采用聚焦变换思想,可直接处理相干宽带信号,对于实际水声信号具有更高的适用性.最后通过对研究方法的空间谱仿真分析证明了其正确性和有效性.     

基于光栅光阀可调谐半导体激光器外腔结构的设计研究

目的:提出利用光栅光阀(GLV)来精密调节光栅外腔半导体激光器输出波束的新方法。方法:这种基于光栅光阀的可调谐外腔半导体激光器的结构使光栅光阀与闪耀光栅形成了共焦结构,便于使被选择的波束可以原路返回,经过在谐振腔中振荡,最后输出。结果:这种基于光栅光阀结构的可调谐外腔半导体激光器可以任意控制输出或者被过滤掉的相应波束的数量。结论:利用光栅光阀的特性,这种可调谐外腔半导体激光器能有效地实现激光输出波束的精密调谐,同时也降低了调谐的机械难度。     

一种高能激光系统光路模拟器设计

光路模拟器用于在实验室内模拟激光器激光束聚焦于远处实际靶子上时的激光能量密度分布,主要由球面镜组成。根据使用的球面镜数量的不同以及各球面镜间距离的变化,它可以模拟激光器实际聚焦于某一距离处靶子上的能量密度分布。文中推导出了光路模拟器的焦距及后截距的数学表达式,并用矩阵方法对计算得出的结果进行了验证,结果表明二者符合得很好。最后讨论了光路模拟器在实际使用中存在的一些问题,这对光路模拟器的调校及实际使用具有一定的指导意义。     

基于概率成像的二维波束聚焦冲击定位方法研究

冲击损伤监测是结构健康监测的主要研究内容之一.本文提出了一种基于十字型传感器布置方法的二维波束聚焦概率成像定位算法,采用十字阵列型的传感器布置方法减小了系统盲区,通过二维波束聚焦概率成像方法提高了冲击定位的精度.在二维波束聚焦算法中,波速的准确性是影响结构冲击损伤定位的主要因素,本文通过统计分析得到波速的概率分布函数,带入二维波束聚焦概率成像定位算法中对冲击损伤进行监测,分别得到横向阵列与纵向阵列的概率分布图,对两者进行融合成像可以得到更为精确、科学且直观的冲击损伤定位结果.通过实验研究验证了该方法的有效性与实用性.     

准光学谐振腔测高温超导薄膜表面电阻

研制了工作在94GHz的两球面镜组成的测高温超导表面电阻及其分布的准光学谐振腔测试系统,腔体的Q值高达1.4×105,高斯波束的束腰半径为2.51mm.此方法具有不损伤超导膜片,灵敏度高,并能检测大面积超导薄膜表面电阻均匀性的优点.     

CaF2:Dy2+连续日光光激射器

液氖温度(27°K)下,用于太阳辐射激励的第一台CaF2:Dy2+光激射器已经实现。利用直径约350毫米球面镜聚焦太阳的发射,带有尺寸为25.4×6.35×3.18毫米的工作晶体的杜瓦瓶置于球面镜的焦点处。     

宽带波束域频率聚焦自适应波束形成算法

针对传统时延控制波束形成器无法适应宽带信号接收的问题,提出一种宽带波束域频率聚焦自适应波束形成算法。首先,通过时延控制方法在空间预设方位形成多个独立波束,利用傅里叶变换将多波束数据变换到频域,针对每个频点构造聚焦矩阵,通过聚焦变换将宽带信号对齐到同一参考频率;然后,估计子带聚焦后的协方差矩阵,并进行特征分解得到信号子空间;最后,利用基于特征子空间(ESB)的波束形成方法得到权矢量,实现自适应波束形成。仿真结果表明,该算法能够实现对宽带信号的自适应接收,具有良好的抗干扰能力和稳健性。     

Circular grating coupled DBR laser with integrated focusing outcoupler

We report on the fabrication and operation of a circular grating coupled, AlGaAs-InGaAs surface-emitting distributed Bragg reflector (DBR) SQW laser with an integrated focusing outcoupler. Electron beam lithography and reactive ion beam etching were used to fabricate the laser with a first-order resonant grating for optical feedback and a separate detuned, chirped second-order grating for outcoupling and focusing the beam.     

Broad-range wavelength tuning in DBR lasers with super structuregrating (SSG)

Broad-range wavelength tuning is demonstrated in tunable distributed Bragg reflector (DBR) lasers with the super structure grating (SSG) proposed. The SSG is fabricated by electron beam exposure lithography. The grating performance is measured by transmittance characteristics of the SSG reflector. A maximum tuning range of 63 nm is obtained under the CW condition while keeping a single longitudinal mode. In a 50-nm tuning range, the threshold current variation is as low as 5.0-9.5 mA     

高气压CO2激光器的连续调谐和频率牵引效应的实验研究

本文报道了光栅调谐的多个大气压CO_2激光器的连续调谐和频率牵引的实验研究。在腔内采用了锗棱镜扩束望远镜或球面反射镜扩束望远镜后,提高了色散腔的频率选择性,增大了光栅的受光照射面积,从而实现了基本无牵引效应的连续调谐,并有效地保护了光栅。     

A novel frequency-scanned reflector antenna

Theoretical and experimental results are presented for a frequency-scanned antenna composed of a line source and a frequency-scanned reflection grating that is shaped to a cylindrical reflector. The principle considering is to select the grating geometry such that the first higher-order diffracted wave propagates and serves as the frequency-scanned beam. An analytical solution for the cylindrical reflector geometry that gives a line focus is given. The grating structure considered consists of an array of dipoles placed over a ground plane. The design of the dipole grating for optimum blazing (i.e., for optimal power conversion from the incident wave to the diffracted wave) is discussed. For the theoretical analysis Floquet's theorem and the method of moments are used     

湍流大气中激光回波到达角起伏

本文运用几何光学近似,导出了湍流大气中束状反射回波的到达角起伏表达式.结果表明:当准直光束和聚焦于反射器的光束照明后向反射器时,回波不存在到达角起伏,而当准直光束照明平面反射器时,到达角起伏是相同条件下视线大气传输光束到达角起伏的一倍.     

A scanning spherical tri-reflector antenna with a moving flatmirror

Spherical reflector systems can achieve pattern scanning without rotation of the main reflector through the use of multiple subreflectors that can move. Also, two subreflectors can be shaped to correct for spherical aberration and to control the aperture distribution on the spherical main reflector. In a previous paper (see ibid., vol.41, p.778, no.6, 1993) we introduced a method that offers both aperture phase and intensity control and scans the main beam without an accompanying movement of the illuminated area over main reflector. The method can overcome the poor aperture utilization problem common in spherical reflector antenna systems; however, it requires motion of the entire subreflector system, including the feed, during scan. In this paper we discuss a method that does not require motion of the subreflector system during scan. This method employs a flat mirror that creates a virtual image of the subreflector system. The motion of the subreflector system in the previous design is replaced by the motion of the virtual image that is controlled by the motion of the flat mirror. The new design offers simplified mechanical motion, while maintaining beam efficiency performance comparable to that of traditional spherical tri-reflector scanning antennas, but with some sacrifice in aperture efficiency and cross-polarization performance     

A new planar grating-reflector antenna

A planar grating-reflector antenna with frequency-scanning properties is presented. The antenna system is composed of a point feed and a planar reflector consisting of a frequency-scanned reflection grating. The grating geometry must be selected such that the first higher-order diffracted wave propagates and serves as the frequency-scanned beam. A focus feed position for the diffracted field is obtained by allowing the lattice geometry to vary along the reflector surface. Methods for analyzing and designing the new antenna configuration are presented. The antenna concept is demonstrated theoretically and experimentally by the design, evaluation, and test of an experimental antenna operating over the frequency band 9.5-10.5 GHz     

A novel Smith-Purcell free electron laser

An experiment on a novel Smith–Purcell free electron laser (FEL) is described in this paper. The FEL is driven by a relativistic sheet electron beam of middle energy. The high frequency system of the device is a quasi-optical resonator composed of a diffraction grating and a three-mirror reflector. Coherent radiation with a peak power of tens of kW at the 3 mm waveband is sucessfully detected from an experimental facility. The main experimental parameters are: sheet beam energy from 400 kV to 500 kV; pulse length of voltage 70 ns; pulse beam current 0.2 kA; synchronous guide magnetic field up to 1.2 T with 10 ms pulse length; and grating period 2.2 mm.     

增益光栅在全息激光振荡器中的应用

增益光栅作为一种动态衍射元件,可构成一种环形腔,只需一束光波即可形成光栅并产生位相共轭波,因此该现象被称为自泵位相共轭(SPPC)。SPPC环形谐振腔具有修正位相失真的功能。由于其具有远大于1的反射率,用一个部分反射器取代输入光束,则系统就成为自启动的。在增益介质中写入体积增益光栅可用于高功率激光系统中光束质量的控制。本文综述了增益光栅的瞬态动力学特性和频谱滤波特性以及各种类型光栅在自启动全息激光振荡器中的贡献。     

新型史密斯-帕塞尔效应可调辐射源研究

提出采用中等能量的相对论环状电子注激励轴对称三曲面反射镜、绕射光栅系统，产生毫米波、远红外波段辐射的新型准光学可调辐射源实验方案，这是一种基于史密斯一帕塞尔效应的自由电子激光。由于引入新型准光学谐振腔系统，可以改变能量输出方向的角度，从原理上讲，可制造一系列模型，产生可调频率的短毫米波、远红外波段相干辐射。采用环状电子注比带状电子注稳定性高，便于成型和聚焦；采用新腔体后增长了电子注与高频场的互作用范围；新型准光腔具有较小的绕射损耗。新方案的这些特点，进一步提高器件的输出功率，改善了高频特性。介绍这种新辐射源在3mm波段的粒子模拟计算初步结果，其输出功率达数百千瓦以上；同时给出准光学谐振腔高频系统的模拟计算和冷测实验的典型曲线。