Influence of magnetic spin resonance in optically transparent magnets on the character of laser radiation

The influence of electron spin resonance on laser radiation from a crystal, one of whose end-faces has been cut at the Brewster angle, is examined. It is shown that modulation of the intensity and polarization of the generated light should hold for definite, critical values of the Faraday rotation angles. A change in the structure of the laser frequency modes also hence occurs. The critical values of the angles of rotation can be attained by altering the direction and magnitude of the external magnetizing field.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 35–39, April, 1973.     

布儒斯特角切割LiNbO3晶体的偏振态分析

基于琼斯矩阵和菲涅耳公式,建立了偏振光透过LiNbO3晶体的分析模型,研究了入射光偏振态、晶压等参数对输出光偏振态和p偏振态、s偏振态透射率的影响规律。搭建了分别含单块LiNbO3晶体、LiNbO3晶体和薄片、两块串联LiNbO3晶体的Ho,Tm,Cr:YAG激光电光调Q实验装置,并测得了输出激光的偏振态、输出能量等随晶压的变化关系曲线。     

Cavity-enhanced optical frequency doubler based on transmission-mode Hänsch–Couillaud locking

A variant of the Hänsch–Couillaud technique for locking the pump laser frequency to a cavity-enhanced optical frequency doubler is presented. In contrast to the original scheme in which the pump laser light reflected by the enhancement cavity is monitored, the error signal for locking is obtained by polarization analysis of the light transmitted by the cavity. The cavity serves as a spectral and spatial filter for the pump beam, making the transmission-mode locking method particularly useful if the beam quality is poor. Experimental validation of the method is demonstrated by generating more than 190 mW of stable 461 nm light from a cavity-enhanced frequency doubler that is pumped by a diode laser system.     

可调谐掺钛蓝宝石激光器的一种新型倍频器

介绍掺钛蓝宝石激光器的一种新的倍频系统,利用色散棱镜对把不同频率的激光从窨色散开,然后利用透镜使这些光从不同方向入射到ＢＢＯ晶体上,这些方向恰 好是这些光的ＢＢＯ晶体上的相位匹配角,从而不需倍频晶体在掺钛蓝宝石激光器的可调谐范围内均实现角度相位匹配。     

Tunable,continuous-wave,ultra-violet radiation around 300 nm by frequency-doubling a rhodamine 6G dye laser

By frequency doubling a cw Rhodamine 6G dye laser using an ADP crystal placed in the laser cavity, in excess of 30 mW of cw uv radiation has been generated. The radiation is tunable over the range 285–315 nm. The ADP crystal is cut with Brewster angle ends, and is located at the focus of cavity compensated for coma and astigmatism. Conversion efficiency is shown to be limited by the onset of thermally induced phase mismatching. Peak uv power can be increased to 85 mW by chopping the radiation from the pumping laser.     

Strong resonance reflection of polarized light from an alkali vapor

Resonance reflection of light from the interface between a dielectric and an alkali vapor is studied. Two cases are considered in which a laser light beam is polarized either parallel or perpendicular to the plane of incidence. Upon scanning of the frequency of the incident laser radiation, in the first case, the reflection conditions vary from approximately the conditions of Brewster reflection to the conditions characteristics of total internal reflection. In the second case, the Brewster reflection conditions are not realized, and the variations in the intensity of the reflected light observed upon frequency scanning are smaller. The rotation of the plane of polarization and the laser frequency tuning make it possible to rapidly switch between these reflection conditions.     

均匀等离子体光栅的色散特性研究

最近研究表明,两束交叉激光脉冲在等离子体中传播时,可以诱导生成周期等离子体密度调制(或称等离子体布拉格光栅). 分别利用传输矩阵法和耦合模理论,推导了激光斜入射时等离子体光栅的色散关系. 两种方法均表明,均匀等离子体光栅存在着光子带隙结构,并且在带隙附近有强烈的色散. 当激光斜入射时,带隙结构会呈现不同的偏振特性：S偏振光的带隙宽度随着入射角的增大而逐渐变宽,而P偏振光的带隙宽度随着入射角的增大先迅速变窄,在布儒斯特角入射时带隙消失,然后又随着入射角的增大而迅速变宽. 超宽的光子带隙和超高的激光损伤阈值,使得等离子体光栅有望成为一种新型的操纵强激光脉冲的光子器件. 关键词： 等离子体光栅 传输矩阵法 耦合模理论 光子带隙     

Fibre laser cutting of thin section mild steel: An explanation of the ‘striation free’ effect

This paper presents the results of an experimental and theoretical investigation into the phenomenon of ‘striation free cutting’, which is a feature of fibre laser/oxygen cutting of thin section mild steel. The paper concludes that the creation of very low roughness edges is related to an optimisation of the cut front geometry when the cut front is inclined at angles close to the Brewster angle for the laser-material combination.     

Simple and accurate measurement of the absorption coefficient of an absorbing plate by use of the Brewster angle

We propose a simple and accurate method for measuring the refractive index and the absorption coefficient of an absorbing parallel plate. The method is essentially based on transmittance measurement with minimum reflectance at the Brewster angle for p-polarized light, which enables us to measure a low absorption loss of the order of 0.1 dB/cm for a typical plate thickness of 1 mm. The error that is due to the approximation used is practically negligible, and the accuracy of measured results depends mainly on the variations in the flatness and parallelism of the two surfaces of the sample and on instrumental errors.     

LD抽运的Nd:YAG陶瓷/KTP绿光激光器

报道了一种LD端面抽运Nd:YAG陶瓷、KTP腔内倍频的全固态连续波绿光激光器.当抽运功率为21.6 W时,1064 nm基频输出达到11.3 W,光—光转换效率为52.3%.采用Ⅱ类切割的KTP晶体作为腔内倍频介质,在直腔结构下获得了最大功率为1.86 W的532　nm绿光输出,光—光转换效率为7%.输出光斑具有高斯型强度分布,1 W输出时的M²因子约为1.7. 关键词： 全固态绿光激光器 Nd:YAG陶瓷 KTP倍频 直腔     

转换反射中光自旋霍尔效应的自旋堆积方向

从理论上和实验上研究了转换反射中光自旋霍尔效应的自旋堆积方向的方法,建立了描述光束在空气-棱镜界面反射的自旋堆积模型,揭示了横移与光束入射偏振角的定性关系。研究发现,当入射角小于布儒斯特角时,随着入射偏振角的逐渐增大,自旋堆积的方向发生反转。而当入射角大于布儒斯特角时,自旋堆积的方向不再随入射偏振角的变化而反转。结果表明,在光束入射角为确定值且小于布儒斯特角的情况下,可以通过调控光束的入射偏振角转换自旋堆积的方向。转换自旋堆积方向的研究为有效调控光自旋霍尔效应提供了新的途径。     

用布儒斯特角法同时测定单轴晶体的折射率和光轴方向

在理论上分析了光轴任意方向的单轴晶体的折射率．根据布儒斯特角原理,当线偏振光的电场矢量平行于入射面时,通过测出对样品三个表面的布儒斯特角,就能同时确定单轴晶体的折射率和光轴方向．并利用分光计,在光轴不确定的情况下,测定了方解石的两个主折射率和光轴方向．     

海面的激光散射特性

 基于随机面元模型，建立了海面对激光散射的理论模型，详细分析了海面散射的退偏振特性。理论分析表明：除后向外其它方向的散射光都存在部分退偏振现象；但是浮于海面上或悬浮于海面的物体表面对激光散射所具有的退偏振特性明显不同于海面散射的退偏振特性。因此可以根据这些差异来遥感海面的漂浮或悬浮物体，该结论已经被实验证实。     

基于激光偏振特性的水下声信号探测方法研究

水下航行体辐射的声波传播到水-空气分界面上时,会在水表面形成微扰,使水表面元产生微倾角.提出一种利用激光偏振特性对水下声信号进行探测的方法,不直接利用散射光强信息,而是利用激光在布儒斯特角附近入射水表面时,反射光偏振特性随入射角剧烈变化的特点对水表面微扰进行高精度探测.建立了该方法的理论模型,得到了入射波、出射波垂直分...     

激光板条设计

侧面光泵的固体激光工作介质采用端面为布儒斯特角的板条形状有许多优点。文章推导了确定板条结构参数的一组公式，讨论了厚度对泵浦光透射损失的影响，认为厚度不宜小于吸收深度。对于ＹＡＧ 之类高折射材料，尖角内是没有振荡光束通过的，可以磨掉。相应地长度应加大０－１３ 倍厚度。     

Multiple light scattering from metal and dielectric rough surfaces

A numerical study is done on light scattering from one-dimensional random rough surfaces supporting both dielectrics and metals. The influence of the corrugation on the Brewster angle as well as on the angular distribution of transmitted intensity into the dielectric is investigated. The authors also obtain enhanced backscattering in the light reflected from metallic surfaces. Finally they discuss the influence of roughness on the drop of reflectance due to polariton absorption.     

La_3Ga_5SiO_(14)电光调Q的Nd∶LiYF激光器研究

报道了以Nd∶LiYF(Nd∶LYF)为增益介质、用硅酸镓镧(La3Ga5SiO14,LGS)晶体进行电光调Q的非稳腔调Q激光器的脉冲特性。Nd∶LiYF的两端按σ偏振1.053μm光的布儒斯特角切割,不需另加起偏镜,实现了单一偏振光振荡。LGS晶体电光Q开关插入损耗小(2%),抗光伤阈值高(950MW/cm2),与DKDP相比,具有不潮解等优点。当抽运能量为120J、重复率3Hz时,单脉冲输出能量为275mJ,脉冲宽度为8ns,动静比为76%,输出能量不稳定度小于3%,偏振度大于99%,光束发散角为0.7mrad。文中还对本激光器偏振特性、非稳腔设计、LiYF导热性能和热透镜效应补偿进行了分析,对LGS电光调Q开关工作性能、工作方式以及存在的问题也进行了分析。     

Selective beam incidence angle control over directional light transmission

A new method for light transmission control is described. Beams pass through directionally transmitting stripes alternating with reflecting, absorbing, or scattering stripes. The mutual arrangement of alternating stripes on two surfaces ensures the incidence angle selectivity of light transmission. A method of grapho-analytical computation is proposed for estimating the effect of geometrical and optical parameters of the stripes on the control characteristics.     

Diode end-pumped high-power Q-switched double Nd:YAG slab laser and its efficient near-field second-harmonic generation

We reported on an all-solid-state double Nd:YAG slab laser. The laser was based on two diode end-pumped Nd:YAG slabs and a stable-unstable hybrid resonator. A cw output of 189 W and an average Q-switched output of 169 W at 10 kHz with an M(2) factor of 1.5 in the slow direction and 1.7 in the fast direction were obtained. We demonstrated efficient near-field frequency doubling by imaging the one-dimensional top-hat near-field to a lithium triborate frequency doubler. We obtained 93 W green light at 10 kHz with a pulse width of 10.7 ns. The efficiency of second-harmonic generation was up to 57%.     

Multiple light scattering from metal and dielectric rough surfaces

Abstract

A numerical study is done on light scattering from one-dimensional random rough surfaces supporting both dielectrics and metals. The influence of the corrugation on the Brewster angle as well as on the angular distribution of transmitted intensity into the dielectric is investigated. The authors also obtain enhanced backscattering in the light reflected from metallic surfaces. Finally they discuss the influence of roughness on the drop of reflectance due to polariton absorption.