激光器

0632177医用二氧化碳激光器波长问题的研究[刊,中]／黄丹／／量子电子学报．-2006,23(5)．-711-713,718(L)从医疗应用的角度出发,研究二氧化碳激光器输出的激光波长不在10．6μm附近的问题。通过理论分析和实验研究证明二氧化碳激光跃迁谱线是丰富性的,在9μm到11μm之间,并对二氧化碳激光治疗机在激光波长参数上的控制提出了建议。参7 0632178飞秒脉冲作用下两种多孔微结构光纤超连续谱的产生[刊,中]／宋学鹏／／量子电子学报．-2006,23(5)．- 692-695(L) 0632179溴化亚铜激光放电管径向声波共振现象研究[刊,中]／马涛／／量子电子学报．-2006,23(5)．-617-620(L) 0632180相干反馈无序激光器循环光散射探讨[刊,中]／付方正／／量子电子学报．-2006,23(5)．-613-616(L) Cao提出了相干反馈无序激光是由循环光散射(即多重散射形成回路)而产生的观点．但未指出不同     

光反馈对光纤光栅外腔半导体激光器特性的影响

主要研究了外加光反馈对光纤布拉格光栅外腔半导体窄线宽激光器特性的影响。在研究温度对光纤光栅外腔半导体激光器激射波长影响的基础上,设计了强度可调的外加光反馈系统,并利用延时自外差法测试外腔半导体激光器的线宽,从实验上分析了不同强度的外加光反馈对外腔半导体激光器线宽和噪声的影响。实验结果表明,在外加光反馈强度逐渐增强的过程中,激光器线宽逐渐变窄。当反馈比为-22dB时,激光器线宽被压窄至原始线宽的15%。与此同时,在相同的反馈变化下,激光器的相对强度噪声开始无明显变化,直到反馈比达到-27dB。再继续增大反馈强度,相对强度噪声显著增大,激光器内部发生相干崩塌。     

从等效电路模型分析激光光源的啁啾特性

在已有的分布反馈激光器的电路模型中引入位相回路,从而使这种电路模型能够携带出射光的位相信息,进而反映激光器的啁啾特性.对修正后的模型进行仿真,结果与已报道的结果十分吻合.进一步将这种带位相回路的激光器模型与电吸收调制器的电路模型相结合,构成分布反馈激光器与电吸收调制器集成光源的等效电路模型.该模型同时考虑了激光器与调制器之间的电耦合.这种由于隔离电阻不够大而导致的电耦合将导致激光器激射波长发生漂移,即产生啁啾.通过对电路模型进行仿真,给出不同隔离电阻时的啁啾特性曲线,并对啁啾大小与隔离电阻的关系进行讨论.结果显示了集成光源相比于直接调制激光器在啁啾特性方面的显著改善.     

高功率半导体激光器线阵列的波长锁定技术

高功率半导体激光器光谱随温度和工作电流的变化比较大,光谱线宽比较宽,这些缺点直接限制了其实际应用.因此,高功率半导体激光器波长稳定技术的研究是激光领域的一个重要研究方向.对波长稳定技术进行研究.实验用体布拉格光栅(VBG)作为反馈元件与高功率半导体激光器线阵列,构成可以对其波长进行锁定的外腔激光器.分析了外腔激光器的波长锁定效果与高功率半导体激光器工作电流、冷却温度、工作电流的占空比和"smile"现象等因素的关系.研究结果表明,高功率半导体激光器的工作电流、冷却温度、工作电流的占空比会影响其激射波长,当激射波长与VBG的布拉格波长差值小于3.0 nm时,可以得到较好的波长锁定效果,而阵列本身的"smile"现象对其波长锁定的影响不大.     

采用模拟PID控制的DFB激光器温度控制系统研制

以红外分布反馈激光器激发光源为核心的检测装置中,分布反馈激光器发光波长的控制精度及稳定性直接决定检测装置测量准确性。为此研发了一种采用模拟PID控制的分布反馈激光器温度控制系统。该系统采用模拟比例-积分-微分温度前向控制模块和温度实时后向采集模块达到控制温度的目的。温度控制实验中采用激射中心波长为2 049 nm的分布反馈激光器,结果表明,系统温度控制稳定性为0.05℃,稳定时间小于30 s。同时,利用所研制的温度控制系统对上述可调谐DFB激光器做了光谱测试实验,结果表明,当激光器驱动电流固定时,激光器激射波长与其工作温度呈线性关系。     

激光振幅与位相涨落对阵列波导CO2激光器输出光相干性的影响

本文利用准单色光的相干理论,分析了阵列波导CO2激光器输出同相态和反相态的原因,从而解释了相干态的持续时间,提出了两态的相互竞争现象是因激光器内部各种噪声造成的观点.有关的实验工作正在进行中.     

液晶随机激光辐射研究进展

随机激光辐射源自激活无序介质,通过辐射光在介质中的多次散射提供光学反馈,无需外加谐振腔.借助液晶的温度和电场依赖性,以液晶为无序介质的随机激光辐射能够呈现出有效的温度控制特性和电场控制特性,为随机激光器的实际应用开辟了新的方法和途径,具有巨大的应用前景.系统介绍了液晶随机激光辐射的基本原理、实现方法及实验结果,回顾了目前的研究现状,提出了以后可能的研究方向.     

无序介质的非相干背散射

讨论两种散射,导出相应的分布函数,运用蒙特卡罗法模拟光子在无序介质中的随机行走过程,得到非相干背散射空间分布及反射率。计算结果表明：1、散射不同,非相干背散射空间分布和反射率不同,非相干背散射反射率随光入射角增大而增大;2、非相干背散射反射率随无序介质吸收系数增大而减小,通过测量非相干背散射反射率可得吸收系数,进一步可得每次散射光子被微粒吸收的概率;3、非相干背散射反射率随光子平均自由程增大而减小,通过测量非相干背散射反射率可得平均自由程,这比检测相干背散射来得到平均自由程要容易。最后,讨论了背散射对无序激光器的影响。     

ZnO纳米多晶颗粒的受激发射及时间分辨特性

以尿素为沉淀剂,采用均匀沉积法与硝酸锌反应获得了ZnO的纳米多晶颗粒.在飞秒脉冲激光激发下,观察到了ZnO纳米多晶颗粒的受激辐射现象,并从频域和时域两方面研究了ZnO纳米多晶的室温激射特性.氧化锌多晶颗粒中出现激子-激子散射导致的激射阈值为7.2 GW.cm-2,激射模式类似于F-P谐振腔模式,时域谱表现为寿命曲线中出现快速衰减成分.P带时间衰减具有对称结构,高斯拟合结果只有几个皮秒.     

二台光激射器的位相同步

贝尔电话实验室的科学家L. H.恩娄（Enloe)和J. L. 罗德（Rodda)作了两台光激射器的位相同步的实验。他们设计出一种反馈回路,它能使两台单频氦-氖光激射器产生的波动相差小于1/3度。     

Random lasing in vertical ZnO nanorods

Random lasing with coherent feedback is detected in the array of vertical ZnO nanorods synthesized on a Si(100) substrate. Under high-intensity optical pumping at the wavelength of 337.1 nm at room temperature, several narrow laser peaks with the width of 0.1 nm are observed in the wavelength region around 392 nm. The laser radiation is emitted in a direction orthogonal to the axis of the nanorods. Study of the behavior of the laser spectrum with the excited area shows good agreement of the data with the theory of random lasers. The mechanism of laser emission is related to the formation of closed paths of light due to multiple coherent scattering at the vertically oriented ZnO nanorods.     

Formation conditions of random laser cavities in annealed ZnO epilayers

The possibilities to realize room-temperature random laser action in ZnO epilayers with MgO as the buffer layer are studied. It is found that the formation of random laser cavities inside the ZnO epilayers can be achieved by post-growth annealing. Incoherent and coherent random lasing phenomena are observed from ZnO epilayers with (220)- and [200]-oriented MgO buffer layers, respectively. Lasing linewidth of the ZnO epilayers with incoherent and coherent feedback under 355-nm optical excitation is found to be /spl sim/4 and /spl sim/0.4 nm, respectively.     

胆甾型液晶溶液膜中的随机激光

研究了激光染料若丹明6G(R6G)在乙基氰乙基纤维素[(E-CE)C]/丙烯酸(AA)胆甾型液晶溶液中的随机激光行为.发现在没有添加任何固体散射粒子的情况下,在(E.CE)C/AA/R6G溶液中观察到多个分离激光峰,最小半峰全宽(FWHM)为0.3 nm,表现出相干反馈行为.这种相干反馈激光行为的形成可能与液晶溶液中胆甾型微区的选择性反射和其折光指数各向异性密切相关.     

Sol-gel ZnO-SiO/sub 2/ composite waveguide ultraviolet lasers

Random laser action with coherent feedback is realized in ZnO-SiO/sub 2/ composite films, which consists of ZnO clusters embedded in SiO/sub 2/ dielectric matrix prepared by sol-gel technique. The films are deposited on silicon substrate with a SiO/sub 2/ buffer layer to form a waveguide structure. Ultraviolet lasing at room temperature is observed from the composite films with ZnO : SiO/sub 2/ molar ratio varying between 1 : 5 and 1 : 30. The corresponding lasing wavelength and linewidth under 355-nm optical excitation are found to be /spl sim/388 nm and less than 0.6 nm, respectively. Our experiment has shown that the proper control of light confinement inside the random cavities leads to coherent random lasing.     

Edge-Emitting Vertically Aligned ZnO Nanorods Random Laser on Plastic Substrate

Random laser action with in-plane coherent feedback has been realized in vertically aligned ZnO nanorods on plastic substrate. A polycarbonate substrate coated with a thin layer of ZnO template was used to grow the nanorods by an aqueous chemical method. It can be shown that there are some restrictions on the dimensions of the ZnO template and nanorods that can be used to achieve in-plane random lasing action. Furthermore, the lasing characteristics of the ZnO nanorods under deformation (i.e., bending the substrate) are investigated. It is found that the lasing performance of the ZnO nanorods on plastic substrate depends on the direction of bending.     

High-power single-mode ZnO thin-film random lasers

The possibilities to realize high-power single-mode ultraviolet lasing in highly disordered zinc oxide (ZnO) thin films are investigated. An effective one-dimensional time-domain traveling-wave model is developed to simulate random laser action in ZnO thin-film waveguides with ridge structure. Spectral and spatial redistributions of lasing modes, due to lasing mode localization and repulsion, are shown in highly disordered media. Hence, by controlling the photon density distribution, selective excitation of lasing modes can be achieved. A coupled-cavity ZnO thin-film random laser is also proposed to achieve high-power single-mode operation under nonuniform pumping. Preliminary experimental results have verified the possibility to realize high-power single-mode emission by the use of the proposed coupled-cavity design.     

Metal-oxide-SiO/sub 2/ composite ZnO lasers

The use of metal-oxide-SiO/sub 2/ composite to sustain random lasing in ZnO thin films is proposed. It is shown that the presence of stripe pattern in the metal-oxide-SiO/sub 2/ composite is necessary to minimize lasing threshold and achieve directional emission. By controlling the concentration of the metal-oxide and stripe spacing, coherent lasing threshold and linewidth of /spl sim/85 kW/cm/sup 2/ and /spl sim/0.4 nm, respectively, can be obtained from mirrorless ZnO thin-film waveguide lasers.     

Collagen network as the scaffold for spontaneously distributed optical resonators

The idea behind this work was to acquire one dimensional lasing in the Rhodamine 6G dye doped collagen fibers with the control of random lasing phenomenon properties by changing the dye molecular arrangement. We show that a simple manipulation of the dye concentration in biopolymeric fibril matrix bulk and an additional use of α-cyclodextrin (α-CD) molecules determine formation of specific dye aggregates and as a consequence the shift of the random lasing emission wavelength in the desired direction. The analysis of the light transport mean free path in function of the dye and (α-CD) concentration was done with the use of coherent back scattering technique.     

DFB LD在光声气体检测系统中的应用研究

针对选用分布反馈激光二极管(DFB LD)作为激励光源的光声气体检测系统,首先分析了温度和注入电流对激光稳定性(包括激射波长和输出光功率)的影响.然后提出了一种蝶形封装的DFB LD在光声甲烷检测系统中的应用方案.实验结果表明,该方案的温控系统和波长调制驱动模式可以产生稳定可靠的光声信号,具有一定的参考价值.最后根据现...