Photoluminescence of CdHgTe solid solutions subjected to low-energy ion treatment

The photoluminescence (PL) of CdHgTe solid solutions subjected to low-energy ion treatment is studied. A blue shift of the peaks in the PL spectra is observed immediately after ion treatment, which is attributed to the formation of a high concentration of donor defects and to the Burstein-Moss effect. The change in the shape of the PL spectra and, in particular, the disappearance of lines associated with transitions to acceptor states indicate that these defects are formed by the interaction of interstitial mercury atoms introduced into the sample during the course of treatment with impurity atoms. As the treatment is terminated, the electron concentration decreases due to the disintegration of defects and the blue shift disappears, but the shape of the spectra remains unchanged. This behavior of the PL spectra can be used for diagnostics of the defect-impurity structure of CdHgTe.     

Effect of laser irradiation on the photoconductivity and noise in n-Cdx Hg1−x Te single crystals

The effect of nanosecond laser radiation on the photoconductivity and 1/f noise in Cd_xHg_1−x Te crystals has been investigated. It is shown that laser irradiation decreases the photosensitivity of the samples and produces a short-wavelength shift of the maximum and the long-wavelength edge of the photoconductivity spectrum. The intensification of 1/f noise and the increase in its frequency are due to a laser-induced increase in the defect density in the material. Fiz. Tekh. Poluprovodn. 31, 820–822 (July 1997)     

Modification of the electrical and photoelectric properties of Mg0.15Cd0.85Te solid solutions as a result of pulsed laser irradiation within the transparency range

Changes in the equilibrium conductivity and photoconductivity of Mg_0.15Cd_0.85Te solid solutions exposed to pulsed laser radiation at a frequency from the transparency range of the crystal are studied as a function of the laser fluence. An increase in the photoconductivity and a shift of the photoconductivity long-wavelength limit to higher energies are found. A change in the electrical properties of the crystals is attributed to an increase in the concentration of donors with ionization energies E ₁=0.015 eV and E ₂=0.035 eV in the surface region. Possible causes and mechanisms of the changes in the photoelectric properties of the II-VI crystals exposed to laser radiation are analyzed.     

Effect of melting on the acoustic response of CdTe and GaAs subjected to the pulsed laser irradiation

The effect of a threshold process of surface melting on the acoustic response in CdTe and GaAs subjected to pulsed laser radiation is considered and the mechanisms of excitation of sonic signals are analyzed. Melting thresholds of the surface of binary compounds CdTe and GaAs are established under irradiation by pulses of nanosecond duration of ruby and neodymium lasers from measurements of the amplitude of the acoustic response.     

Specific features of photoconductivity spectra of the CdTe/CdHgTe epitaxial graded-gap heterostructures

Based on studies the structural and photoelectric properties of CdTe/CdHgTe graded-gap heterostructures, it is found that the metallurgical interface between the materials, which is located in the structure bulk, is enriched with structural defects. An increased recombination rate is characteristic of this interface. This circumstance is the cause of the loss of photosensitivity in the mid-IR range of the broadband photoconductivity spectra of these heterostructures. For the epitaxial layers thinner than 10–20 μm, the effect of the metallurgical interface can manifest itself in the reduction or complete loss of photosensitivity.     

脉冲激光照射生物组织的压强效应

激光生物学效应的机理非常复杂。在激光照射下,组织变性甚至被切割激光的热效应和     

放电引发非链式DF激光器脉冲特性研究

研究了工作气体分压比、总气压、充电电压及输出镜反射率对激光单脉冲能量、脉冲宽度及峰值功率的影响。实验结果表明:对于输出能量,工作介质SF6和D2的分压比为10:1及输出镜反射率为30%时最佳,正常辉光放电状态下提高充电电压有利于增加单脉冲能量,且对于每个电压存在使能量最大的最佳气压值。激光脉冲宽度随工作气体分压比及总气压的增大不断变窄,但随充电电压和输出镜反射率的升高不断变宽。综合考虑输出能量和激光脉宽,激光峰值功率的总体变化趋势与能量一致,但二者取得最大值所对应的气体参数及输出镜参数存在差别。     

On the problem of internal optical loss and current leakage in laser heterostructures based on AlGaInAs/InP solid solutions

Semiconductor lasers based on MOCVD-grown AlGaInAs/InP separate-confinement heterostructures are studied. It is shown that raising only the energy-gap width of AlGaInAs-waveguides without the introduction of additional barriers results in more pronounced current leakage into the cladding layers. It is found that the introduction of additional barrier layers at the waveguide–cladding-layer interface blocks current leakage into the cladding layers, but results in an increase in the internal optical loss with increasing pump current. It is experimentally demonstrated that the introduction of blocking layers makes it possible to obtain maximum values of the internal quantum efficiency of stimulated emission (92%) and continuouswave output optical power (3.2 W) in semiconductor lasers in the eye-safe wavelength range (1400–1600 nm).     

Output power characteristics of the pulsed argon ion laser

The output power of pulsed noble gas ion lasers is discussed in terms of dependence on gain, plasma tube length, current density, and excitation mechanisms. Experimental data for some of the strong laser transitions of singly ionized argon in pulsed operation are presented. The resulting power output dependence on current density suggests that two-step excitation plays an important role, particularly in the population of the lower laser levels. This point of view is consistent with observation of ring formation in the output beam cross section, and of the output power dependence on thefrac{3}{2}power of the plasma tube diameter.     

Photoluminescence of cadmium telluride recrystallized by nanosecond pulsed laser irradiation

The influence of nanosecond pulsed laser irradiation on the morphology and low-temperature photoluminescence of n-type CdTe at energy densities sufficient to melt the material (0.2–0.5 J/cm²) is investigated. After recrystallization the material has an “orange-peel” appearance. The low-temperature photoluminescence spectrum corresponds to low-grade single-crystalline p-type CdTe containing a large number of dislocations and clusters of point defects. The laser treatment has a long-range effect, significantly altering the impurity-defect system in a way characteristic of n→p conductivity conversion at distances greater than 50 μm from the site where laser radiation is absorbed. Fiz. Tekh. Poluprovodn. 32, 32–35 (January 1998)     

脉冲激光引信烟雾后向散射特性研究

激光引信的探测性能容易受到烟雾的干扰,引起虚警和漏警。为研究脉冲激光引信在烟雾环境中的传输特性,基于Mie散射理论和Monte Carlo方法,建立脉冲激光引信烟雾后向散射模型,仿真905 nm脉冲激光在不同烟雾环境下的回波特性,进行相关试验,对比仿真归一化峰值强度与实测峰值电压,进行相关性分析,验证模型的准确性。分析不同烟雾质量浓度、烟筒长度与距离下脉冲激光引信在烟雾环境中的后向散射特性,得到不同条件对回波的影响规律,研究结果可为脉冲激光引信抗烟雾干扰提供支撑。     

脉冲激光诱导石墨等离子体羽辉特性研究

为了研究C₂的演化规律,采用增强型电荷耦合器件（ICDD）直接成像法,通过Nd:YAG激光器烧蚀石墨靶,使用窄带通滤波片分辨出C₂和C+的发射位置,研究了在不同空气压力条件下,脉冲激光诱导石墨等离子体中C₂和C+的发射特性。当空气气压为10-2Pa和3Pa时,C₂发射峰值位于靶材附近,此时C₂的形成主要为靶材的直接发射;气压增大至50Pa时,由于气相重组反应加强,等离子体前端出现另一个C₂的发射峰值,其峰值位置与C+一致,并且其逐渐占C₂发射的主导地位,此时C₂的形成主要来源于重组反应,C+发射光强要大于C₂;当气压进一步增大至130Pa时,气相重组反应增加,在等离子体前端出现C₂的发射强度增强,在1.3μs之后,C₂的发射强度大于C+。结果表明,随着气压的变化,C₂的发射峰值位置和强度发生明显变化。这一结果对碳等离子体沉积碳纳米材料原理研究是有帮助的。     

Effect of nitrogen pressure on optical properties and microstructure of diamond-like carbon films grown by pulsed laser deposition

The effect of nitrogen pressure on optical properties of hydrogen-free diamond-like carbon (DLC) films deposited by pulsed laser ablation graphite in different background pressures of nitrogen is reported. By varying nitrogen pressures from 0.05 to 15.00 Pa, the photoluminescence is gradually increased and optical transmittance is gradually decreased. Atomic force microscopy (AFM) is used to observe the surface morphology of the DLC films. The results indicate that the surface becomes unsmoothed and there a...     

Optimization of the optical output in a C-to-C pulsed gas laser

An investigation of the optimum condition for maximum optical output in a C-to-C pulsed gas laser (N₂ laser) showed that this condition does not happen when the two capacitances are equal (C ₁=C₂) as this happens in the “Doubling circuit” case, but when the peaking capacitance obtains a critical value. This behavior is attributed to the electric pumping pulse formed by the temporary loading of the peaking capacitor. This electric pumping pulse increases as the peaking capacitor increases. However, for low values of the peaking capacitor the optical output follows the rise of the electric pumping pulse. On the other hand, for higher values of the peaking capacitor than a critical one, a part of the electric energy arrives at the laser channel after the laser output, while the exploitable electric energy decreases causing reduction of the optical output     

脉冲激光轰击固体表面产生的等离子体的实验研究

本文对Nd:YAG脉冲激光在大气中轰击块状YBaCuO超导材料产生的等离子体进行了研究。首先,用光纤采集等离子体的辐射,由一台OSA接收并识别。然后利用光纤及单色仪跟踪发光粒子,得到了粒子的发光强度随垂直靶面距离的变化。测得了各种发光粒子在不同位置处的发光强度-飞行时间波形,并对实验结果进行了分析。     

脉冲染料激光对小鼠中性粒细胞移动的影响

用YAG倍频泵浦染料激光体外照射小鼠外周血,以微孔滤膜法检测其对中性粒细胞移动的影响。结果表明,在610nm～680nm范围内细胞趋化运动的促进或抑制作用与激光作用于细胞是液的累积剂量有关,而且与激光的波长有显著依赖关系。     

不同波长脉冲染料激光照射视网膜的生物效应比较

本文采用三种不同有机染料作激活介质,比较了不同波长的短脉冲(μs级)激光对视网膜的急性生物效应。 实验条件与方法 采用DOL-3型眼科用染料激光器,分别用Coumarin 504、Rh6G等染料作激活介质,获得绿色(520nm)、橙色(590nm)和红色(630nm)的激光,脉冲能量为4mJ左右,光斑直径200μm。视网膜激光曝光时间为1.6μs。     

Inversion of the conduction type of epitaxial films of PbSnTe solid solutions under the influence of laser irradiation at subthreshold power

Conduction type inversion processes in Pb_1−x Sn_xTe epitaxial films irradiated by a CO₂ laser (λ=10.6μm) at subthreshold power is investigated. It is hypothesized that the stable inverted state is a result of the formation of neutral metal and chalcogen divacancies. Fiz. Tekh. Poluprovodn. 31, 990–992 (August 1997)     

脉冲激光辐照下金属/液体结构温度变化初探

通过1053 nm重频脉冲激光辐照铝合金板和铝合金/水结构实验,初步研究了水的存在对铝合金板温度变化的影响。采用有限元方法,计算了脉冲激光辐照下铝合金板和铝合金/水结构中的温度场变化。数值结果和实验结果基本相符,水的存在加速了热扩散,延缓了铝合金板的温升。     

脉冲激光沉积法制备红外光学SiC薄膜特性研究

采用脉冲激光沉积法在锗基底制备无氢SiC薄膜,研究了激光能量对SiC薄膜显微结构、成分和红外光学性能的影响规律。利用傅里叶红外光谱仪测量了锗基底SiC薄膜样品的红外透射光谱,其在785 cm-1附近有一个强烈Si-C键特征吸收峰,并在红外波数4 000~1 300 cm-1之间具有良好的透过性。通过对透射光谱拟合计算可知:在红外波段2.5~7.7 m之间,SiC薄膜的折射率和消光系数均随着激光能量的增加而增大,折射率大约从2.15上升到2.33,激光能量从400 mJ增加到600 mJ,且当激光能量为400、500 mJ时,消光系数均在10-3量级以内,光学吸收很小。研究表明,SiC薄膜在红外2.5~7.7 m波段是一种优异的光学薄膜材料。