应变补偿InGaAs/InAlAs量子级联激光器

利用应变补偿的方法研制出激射波长 λ≈ 3.5— 3.7μm的量子级联激光器 .条宽 2 0 μm,腔长 1 .6mm的 Inx Ga1- x As/Iny Al1- y As量子级联激光器已实现室温准连续激射 .在最大输出功率处的准连续激射可持续 30 min以上 .     

应变补偿InGaAs/InAlAs量子级联激光器

利用应变补偿的方法研制出激射波长λ≈3.5—3.7μm的量子级联激光器.条宽20μm,腔长1.6mm的InxGa1-xAs/InyAl1-yAs量子级联激光器已实现室温准连续激射.在最大输出功率处的准连续激射可持续30min以上.     

室温激射应变补偿5.5μm量子级联激光器

利用应变补偿和优化波导结构来提高量子级联激光器的性能,实现了波长为5.5μm量子级联激光器的室温激射.利用双晶X射线衍射实验对材料生长质量进行了检验.对于条宽为20μm,长为2mm的脊形波导激光器,室温最大输出功率为单腔面45mW.     

GaAs/AlGaAs量子级联激光器

利用分子束外延方法生长了激射波长约为9μm的GaAs/Al0.45Ga0.55As量子级联激光器.条宽35μm,腔长2mm的器件准连续激射温度最高达120K,81K下未经收集效率修正的峰值功率超过70mW.     

GaAs/AlGaAs量子级联激光器自脉动动力学

利用步进扫描时间分辨傅里叶变换红外光谱,研究了波长9.76μm GaAs/AlGaAs量子级联激光器的准连续波激射谱.在驱动电流周期内,时间上堆叠的发射谱能够观察到明显的光强自脉动现象.有源区中的自加热积累大大影响了电子的驰豫和输运性质.热引起的在注入区较高子能级中占据的载流子由于这些子能级与下一注入区的连续态形成共振条件而泄露,而耦合阱有源区中第四子能级的存在加快了这个过程.周期性破坏和恢复的共振条件所引起的载流子泄露在很大程度上导致了时域堆叠光谱的自脉动.     

GaAs/AlGaAs量子级联激光器自脉动动力学

利用步进扫描时间分辨傅里叶变换红外光谱,研究了波长9.76μm GaAs/AlGaAs量子级联激光器的准连续波激射谱.在驱动电流周期内,时间上堆叠的发射谱能够观察到明显的光强自脉动现象.有源区中的自加热积累大大影响了电子的驰豫和输运性质.热引起的在注入区较高子能级中占据的载流子由于这些子能级与下一注入区的连续态形成共振条件而泄露,而耦合阱有源区中第四子能级的存在加快了这个过程.周期性破坏和恢复的共振条件所引起的载流子泄露在很大程度上导致了时域堆叠光谱的自脉动.     

低阈值连续波工作的2.9 THz量子级联激光器

为了获得低阈值连续波工作太赫兹源,采用固源分子束外延技术生长了GaAs/AlGaAs束缚态向连续态跃迁的太赫兹量子级联激光器(QCL)有源区,基于半绝缘-等离子体波导工艺制作了太赫兹量子级联激光器。获得了激光器(腔面未镀高反射膜)的发射光谱和相应的输出特性等性能,其中器件在10 K工作温度、350 mA激励电流下的中心频率为2.93 THz,连续波工作模式的阈值电流密度为156 A/cm2,器件的最大光输出功率为7.84 mW,最高工作温度为62 K。     

无需空穴参与的量子级联激光器

无需空穴参与的量子级联激光器过去十年中，紧凑型半导体激光器使几个新技术领域获得发展。最引人注目的有光通信、光数据存储和光盘。但直至今日，半导体激光器只在相当窄的波段（主要是近红外）内得到发展，这点限制了其进一步应用。短波段激光器近来有了高速发展。红光...     

High-power continuous-wave quantum cascade lasers

High-power continuous-wave (CW) laser action is reported for a GaInAs-AlInAs quantum cascade structure operating in the mid-infrared (λ≃5 μm). Gain optimization and reduced heating effects have been achieved by employing a modulation-doped funnel injector with a three-well vertical-transition active region and by adopting InP as the waveguide cladding material to improve thermal dissipation and lateral conductance. A CW optical power as high as 0.7 W per facet has been obtained at 20 K with a slope efficiency of 582 mW/A, which corresponds to a value of the differential quantum efficiency η_d=4.78 much larger than unity, proving that each electron injected above threshold contributes to the optical field a number of photons equal to the number of periods in the structure. The lasers have been operated CW up to 110 K and more than 200 mW per facet have still been measured at liquid nitrogen temperature. The high overall performance of the lasers is also attested by the large “wall plug” efficiency, which, for the best device, has been computed to be more than 8.5% at 20 K. The spectral analysis has shown finally that the emission is single-mode for some devices up to more than 300 mW at low temperature     

Photonic-crystal distributed-feedback quantum cascade lasers

Because of an intrinsically low linewidth-enhancement factor, the quantum cascade laser (QCL) is especially favorable for patterning with a recently proposed 2-D photonic crystal (PC) lattice that substantially increases the device area over which optical coherence can be maintained. In this work, we use an original time-domain Fourier-transform (TDFT) algorithm to theoretically investigate the beam quality and spectral purity of gain-guided PC distributed-feedback (DFB) quantum cascade lasers. The conventional 1-D DFB laser and also the angled-grating DFB (α-DFB) laser are special cases of the PCDFB geometry. By searching the parameter space consisting of tilt angle, coupling coefficients, stripe width, and cavity length, we have theoretically optimized the PCDFB gratings for QCL gain regions. At a wavelength of 4.6 μm, the simulations project single-mode emission from stripes as wide as 1.2 mm, and etendues of no more than three times the diffraction limit for 2-mm stripes. We also examine the tolerances required for single-mode and high-brightness operation. Comparisons are made to analogous simulations of a-DFB QCL lasers     

高输出功率太赫兹量子级联激光器与温度特性

半导体太赫兹量子级联激光器(THz QCL)是一种相干性好线宽窄的太赫兹辐射源,有潜力获得高的输出功率.采用基于非平衡格林函数(NEGF)方法的计算工具设计、生长、制备了基于砷化镓系材料的THz QCL.在10 K温度下,峰值功率达到270 mW,平均功率为2. 4 mW,单位面积的输出功率与已报道的最高值相当.采用NEGF方法对器件的温度变化特性做了详细的分析.     

Bound-to-continuum GaInAs-AlAsSb quantum cascade lasers with reduced electric injection power density

Short-wavelength (/spl lambda/<4 /spl mu/m) GaInAs-AlAsSb quantum cascade (QC) lasers have been demonstrated using a "bound-to-continuum" design for the purpose of reducing the electric injection power density. As a result, we have reduced the low-temperature electric injection power density of the lasers by 40%, compared to that of GaInAs-AlAsSb QC lasers emitting at the same wavelength but adopting a triple-quantum-well design. The lasers in the present report can operate up to room temperature (300 K) in pulsed mode, emitting at short-wavelength /spl lambda//spl sim/3.7-3.9 /spl mu/m.     

GaAs基量子级联激光器材料结构设计的进展

GaAs基量子级联激光器的出现,在器件的设计制作和处理工艺上开辟了有意义的前景。本文概述了近年来GaAs基量子级联激光器在波导核心层、波导以及光学谐振腔方面设计的原理、进展,并介绍了一些新颖的结构。     

太赫兹二级分布反馈量子级联激光器中的模式竞争与功率特性

结合实验和理论计算研究了太赫兹二级分布反馈量子级联激光器中的模式竞争和功率特性.研究表明,激光器在整个动力学范围内均稳定地工作在横向及纵向的基模.横向基模的产生原因是脊条两侧的吸收边界有效提高了高阶横模的损耗.纵向基模的产生原因主要是谐振腔内基模与高阶纵模的电磁场分布交叠较大,并且频率接近,从而有效避免了增益在空间和频域的烧孔效应.此外,激光器的辐射效率随分布反馈光栅长度的增加而减小,导致只有在特定的光栅长度才能获得最大的输出功率.该工作有助于高性能单模太赫兹激光器及锁相激光器阵列的研制.     

InAs-based distributed feedback quantum cascade lasers

InAs/AlSb distributed feedback quantum cascade lasers are presented. The lasers can operate in the single frequency regime at 3.34-3.38 mum in the 0-100degC temperature range in pulse mode. The wavelength tuning rate of the lasers is 0.27 nm/K and continuous tuning range up to 10 nm can be achieved.     

Resonant tunneling in quantum cascade lasers

Experimental evidence that in quantum cascade lasers electron injection into the active region is controlled by resonant tunneling between two-dimensional subbands is discussed. A quantitative analysis is carried out using an equation for the current density based on a tight-binding approximation. Electron injection into the active region is optimized when the current density is limited by the lifetime of the excited state of the laser transition. In this regime, quasi-equilibrium is reached between the population of the injector ground state and that of the excited state of the laser transition characterized by a common quasi-Fermi level. The design of the injector depends on the selected laser active region; in particular, the choice of physical parameters, such as doping concentration and injection barrier thicknesses, is in general different for vertical or diagonal transition lasers. The paper concludes with an investigation of the transport properties at threshold and its dependence on stimulated emission; a relationship between the differential resistance above threshold and the value of the slope efficiency is deduced     

量子级联激光器的原理及研究进展

量子级联激光器的发明是半导体激光器领域里程碑的发展,开创了中远红外半导体激光的新领域,在红外对抗、毒品和爆炸物检测、环境污染监测、太赫兹成像等方向有广泛的应用前景.本文阐述了量子级联激光器的基本原理、以及材料和器件的研究,结合应用方向对其研究进展进行了综述性介绍.     

High-performance quantum cascade lasers with electric-field-freeundoped superlattice

An optimized design of quantum cascade lasers with electric field free undoped superlattice active regions is presented. In these structures the superlattice is engineered so that: (1) the first two extended states of the upper miniband are separated by an optical phonon to avoid phonon bottleneck effects and concentrate the injected electron density in the lower state and (2) the oscillator strength of the laser transition is maximized. The injectors' doping profile is also optimized by concentrating the doping in a single quantum well to reduce the electron density in the active material. These design changes result in major improvements of the pulse/continuous-wave performance such as a weak temperature dependence of threshold (T₀=167 K), high peak powers (100-200 mW at 300 K) and higher CW operating temperatures for devices emitting around at λ~8.5 μm