基于量子级联激光器的红外光谱技术评述

量子级联激光器是一种新型的红外相干光源。利用量子理论与带隙工程,量子级联激光器可实现3 μm到100 μm波长范围内的任意输出波长。由于大多数气体分子的特征光谱都集中在中红外波段,而中红外量子级联激光器具有功率高、线宽窄、扫描速度快等独特的优点,因此,基于量子级联激光器的红外光谱技术已成为气体检测技术的研究热点。尤其是,近年来室温激光器性能得到不断的完善,输出功率和电光转换效率得到了极大的提高,这在很大程度上推动了红外激光光谱技术的迅速发展。本文根据工作原理,分别介绍了基于直接吸收谱检测、相位调制光谱检测、光声调制光谱检测和法拉第旋光效应光谱检测的量子级联激光器红外光谱检测技术,并对其实现方法和应用情况进行了介绍。     

基于QCL的红外吸收光谱技术的研究进展

量子级联激光器作为一种新型的单极型半导体激光器,其峰值发射波长处于中红外波段（2.5~25 μm）,具有功率高、线宽窄、响应速率快等传统半导体激光器所没有的独特优势,且具有较高的探测灵敏度,非常适合中红外波段的气体分子的检测。可广泛应用于大气痕量气体、呼吸气体、燃烧气体、生化气体、机动车尾气、工业废气以及农药残留气体等低浓度气体的检测。因此,利用量子级联激光器对气体分子进行探测在非侵入式医学诊断、环境监测以及工农业生产等领域都具有十分重要的意义。自20世纪末量子级联激光器发明以来,室温激光器的性能得到了长足的进步,也出现了多种结构形式的量子级联激光器。这也使得量子级联激光器红外吸收光谱技术得到了很大的发展。事实上,很多光谱技术在量子级联激光器发明之前就已经得到了发展和应用,而利用量子级联激光器作为光源则在很大程度上扩展了可探测波段,也在一定程度上提高了探测极限。这其中就包括了直接吸收光谱技术、波长调制技术、腔衰荡光谱技术、腔增强吸收光谱技术以及光声光谱等。综述了国内外量子级联激光器进行红外吸收光谱技术的研究现状和发展趋势,分析了量子级联激光器红外吸收光谱技术在发展过程中所遇到的瓶颈以及后期得到的解决方案,比较详细地介绍了各种方法的原理、应用,并指出了在吸收光谱测量中的优缺点,同时对外场痕量气体探测作了简要总结。最后,对量子级联激光器红外吸收光谱技术在未来痕量气体探测上的应用和发展进行了展望,指出随着红外吸收光谱技术的快速发展,这些方法可以得到更有效的改进和发展,进而朝着高灵敏度、高集成度以及高时效方向发展。     

p型掺杂1.3μm InAs/GaAs量子点激光器的最大模式增益特性的研究

对p型掺杂13 μm InAs/GaAs量子点激光器的最大模式增益进行了实验和理论分析.实验上,测量了不同腔长激光器阈值电流密度与总损耗的对应关系,拟合出的最大模式增益为175 cm^-1,与相同结构非掺杂量子点激光器的最大模式增益一致.同时理论分析表明,p型掺杂对InAs/GaAs量子点激光器的最大模式增益并无影响,并且最大模式增益的计算结果与实验值相符.具有较小高度或高宽比的量子点能达到更高的最大模式增益,而较高的最大模式增益对p型掺杂13 μm InAs/GaAs自组织量子点激光器在光通信系统中的应用具有重要意义. 关键词： 最大模式增益 p型掺杂 InAs/GaAs量子点激光器     

硫汞族量子点红外光电探测技术

受限于复杂的分子束外延生长及倒装键合工艺,现有块体半导体红外探测器成本高昂、工艺复杂、极大制约了成像阵列规模和分辨率的进一步提升。胶体量子点作为一种新兴的半导体纳米晶体材料,因“量子限域”效应,能够实现宽谱段范围内的精准带隙调控。同时,胶体量子点可通过液相化学合成方法低成本大批量制备。此外,胶体量子点的液相加工工艺使得其可以与硅基读出电路进行直接片上电学耦合,突破了倒装键合工艺限制。因此,胶体量子点在红外探测及成像领域展现了巨大的应用前景。其中硫汞族量子点具有探测波段范围宽、物性调控易及便于硅基集成等优势,先后实现了中波红外背景限探测、双色探测及焦平面阵列成像等,在红外光电技术展示了巨大的潜力。本综述总结了近年来硫汞族胶体量子点红外光电探测技术的研究现状,并对其未来发展方向进行了展望。     

支撑光网络发展的硅基光电子技术研究

作为大规模集成电路和化合物半导体光电子器件的制造技术共同构成的一门高新技术 ,硅基光电子技术越来越受到重视 .文章着重介绍中国科学院半导体研究所外延生长SiGe/Si量子结构和Si基器件研究的结果 :采用自行设计的UHV/CVD系统 ,成功地生长出Ⅱ型SiGe/Si量子阱和量子点 ,直到 2 5 0K仍能观察到自组织生长Ge/Si(0 0 1 )量子点的发光峰 ;研制成功SiGe/Si谐振腔增强型光电二极管 (RCEPD)、Y分支MZI光调制器和多模干涉 -马赫 -曾德干涉型光开关等Si基光电子器件 ;1 .3μm处RCEPD的量子效率达到 4 .2 % ,- 5V偏压下暗电流密度 1 2 pA/ μm2 ;2× 2热光型光开关的响应时间小于 2 0 μs,两输出端关态串扰为 - 2 2dB ,通态串扰为 - 1 2dB .     

硒化铅核壳量子点的合成与应用研究进展

硒化铅(PbSe)量子点具有宽红外光谱调控范围、高荧光量子产率和可溶液加工等特点,成为一类重要的红外材料体系。与广泛研究的PbS量子点相比,PbSe量子点在空气中容易氧化,从而严重破坏其光电特性,制约了其应用的发展。壳层的包覆是有效提升PbSe量子点光学特性和化学稳定性的策略之一,是推动PbSe量子点应用发展的材料研究方向。本文综述了PbSe核壳量子点的合成及其在光电探测、太阳能电池、激光器和光催化等领域的应用研究进展,希望能够为国内研究者开展相关研究提供参考。     

5.33 μm处磁旋转吸收光谱NO分子探测研究

本文基于直流磁场的磁旋转吸收光谱技术探测研究一氧化氮分子的痕量. 使用5.33 μm连续波量子级联激光器作为探测光源,结合Chernin型光学多通池,在1875.81 cm^-1(²∏_3/2(3/2),υ=1←0)波长处进行探测. 108 m吸收光程下,实现了1.15 ppbv的探测极限(1s,1σ). 当采样时间延长到15 s,探测极限可提高至0.43 ppbv.     

能级构型对InAs/GaAs量子点电磁感应透明介质中光孤子存储的影响

基于现有的实验,利用不同频率的光脉冲耦合到InAs/GaAs量子点的不同能级之间可形成梯形、Λ形和V形等3类量子点电磁诱导透明介质.继而研究这三类能级构型InAs/GaAs量子点电磁诱导透明介质中的光孤子形成和存储性质,结果表明,梯形和Λ形InAs/GaAs量子点体系不但可形成光孤子还可以实现光孤子的存储与读取,且其所存储光孤子的保真度比光存储的保真度高;但V形InAs/GaAs量子点体系却不能形成光孤子,这是由于体系的非线性效应非常弱.有趣的是在相同的实验参数下,Λ形InAs/GaAs量子点体系所存储的光孤子幅度比梯形所存储的光孤子幅度大.这为半导体量子点器件对所存储光孤子进行调幅操作提供了理论依据.     

光栅耦合外谐振腔调谐的半导体量子级连激光器

本文研究了由InGaAs/InAlAs材料组成,波长为4.6和5.1微米的量子级连中红外半导体激光器的光栅外耦合谐振腔的特性。在温度是80K时波长可调制宽度是激光中心波长的1.5%左右。对于这两个激光器而言,它们的波长可调制宽度随温度升高而减低。被调制的单模激光器的输出光功率是几个毫瓦,激光的谱线宽度是1到2个微米。激光阈值电流随波长缓慢变化,然而激光输出效率在短波长时更加优化。     

面向片上传感量子级联激光器的研究进展（特邀）

作为一种新型半导体激光器,量子级联激光器因其独特的子带间跃迁机制,具有高速响应、高非线性、输出波长大范围可调等特点。近年来随着输出光功率和电光转化效率等性能指标的快速提升,量子级联激光器已成为中红外至太赫兹波段（波长约为3～300μm）的主流激光光源,在大气污染监控、气体检测、太赫兹成像、生物医疗以及空间光通信等领域具有重要科学意义和应用价值。本文阐释了量子级联激光器的发展历程以及工作原理;分别重点讨论了中红外量子级联激光器在高效率、大功率、波长可调谐以及片上传感的应用等方面的研究进展,并对基于中红外量子级联激光器差频太赫兹光源和光频梳的发展进行叙述,最后进行了简要总结与展望。     

InAs/GaAs quantum dot infrared photodetectors with different growth temperatures

InAs/GaAs quantum dot infrared photodetectors were fabricated with quantum dots grown at three different temperatures. Large detection wavelength shift (5–14.5 μm) was demonstrated by changing 40 degrees of the epitaxy temperature. The smaller quantum dots grown at lower temperature generate 14.5 μm responses. The detectivity of the normal incident 15 μm QDIP at 77 K is 3 × 10⁸ cm Hz^1/2/W. A three-color detector was also demonstrated with quantum dots grown at medium temperature. The three-color detection comes from two groups of different sizes of dots within one QD layer. This new type of multicolor detector shows unique temperature tuning behavior that was never reported before.     

Demonstration of 640 × 512 pixels long-wavelength infrared (LWIR) quantum dot infrared photodetector (QDIP) imaging focal plane array

We have exploited the artificial atom-like properties of epitaxially grown self-assembled quantum dots (QDs) for the development of high operating temperature long wavelength infrared (LWIR) focal plane arrays (FPAs). QD infrared photodetectors (QDIPs) are expected to outperform quantum well infrared detectors (QWIPs) and are expected to offer significant advantages over II–VI material based FPAs. We have used molecular beam epitaxy (MBE) technology to grow multi-layer LWIR dot-in-a-well (DWELL) structures based on the InAs/InGaAs/GaAs material system. This hybrid quantum dot/quantum well device offers additional control in wavelength tuning via control of dot-size and/or quantum well sizes. DWELL QDIPs were also experimentally shown to absorb both 45° and normally incident light. Thus we have employed a reflection grating structure to further enhance the quantum efficiency. The most recent devices exhibit peak responsivity out to 8.1 μm. Peak detectivity of the 8.1 μm devices has reached 1 × 10¹⁰ Jones at 77 K. Furthermore, we have fabricated the first long-wavelength 640 × 512 pixels QDIP imaging FPA. This QDIP FPA has produced excellent infrared imagery with noise equivalent temperature difference of 40 mK at 60 K operating temperature.     

Optical properties of InAs quantum dots in a Si matrix

We report on the optical properties of nanoscale InAs quantum dots in a Si matrix. At a growth temperature of 400°C, the deposition of 7 ML InAs leads to the formation of coherent islands with dimensions in the 2–4 nm range with a high sheet density. Samples with such InAs quantum dots show a luminescence band in the 1.3 μm region for temperatures up to 170 K. The PL shows a pronounced blue shift with increasing excitation density and decays with a time constant of 440 ns. The optical properties suggest an indirect type II transition for the InAs/Si quantum dots. The electronic structure of InAs/Si QDs is discussed in view of available band offset information.     

InAs QDs on InP: polarization insensitive SOA and non-radiative Auger processes

An efficient mechanical and electronic axial approximation of the strained 8 × 8 Hamiltonian is proposed for zinc-blende nanostructures with a cylindrical shape on (100) substrates. Vertically stacked InAs/InP columnar quantum dots (CQDs) for polarization insensitive semiconductor optical amplifier (SOA) in telecommunications applications are studied theoretically. Non-radiative Auger processes in InAs/InP quantum dots (QDs) are also investigated. It is shown that a multiband approach is necessary in both cases.     

硅BC8量子点太阳能电池中的多重激子效应

多重激子效应是指在纳米半导体晶体中,量子点吸收一个高能光子而产生多个电子-空穴对的过程,该效应可以提高单结太阳电池能量转换效率。利用碰撞电离机制和费米统计模型计算了工作温度300 K的单结硅BC8量子点太阳能电池在AM1.5G太阳光谱下的能量转换效率。对于波长在280~580 nm的入射光,多重激子效应可以大幅增强硅BC8量子点直径d>5.0 nm的量子点太阳电池的能量转换效率。硅纳米量子点的直径d=6.3~6.4 nm时,最大能量转换效率为51.6%。     

Long-wavelength luminescence from GaSb quantum dots grown on GaAs substrates

Self-assembled GaSb quantum dots (QDs) with a photoluminescence wavelength longer than 1.3 μm were successfully grown by suppressing the replacement of As and Sb on the surface of the GaSb QDs. This result means that GaSb can thus join InAs or GaInAs as a suitable material for QD lasers for optical communications.     

Formation of InAs quantum dots in silicon by sequential ion implantation and flash lamp annealing

InAs quantum dots (QDs) were successfully formed in single-crystalline Si by sequential ion implantation and subsequent milliseconds range flash lamp annealing (FLA). Samples were characterized by μ-Raman spectroscopy, Rutherford Backscattering Spectrometry (RBS) high-resolution transmission electron microscopy (HRTEM) and low temperature photoluminescence (PL). The Raman spectrum shows two peaks at 215 and 235 cm^?1 corresponding to the transverse optical (TO) and longitudinal optical (LO) InAs phonon modes, respectively. The PL band at around 1.3 μm originates from the InAs QDs with an average diameter 7.5±0.5 nm and corresponds to the increased band gap energy due to the strong quantum confinement size effect. The FLA of 20 ms is sufficient for InAs QDs formation. It also prevents the out-diffusion of implanted elements. Moreover, the silicon layer amorphized during ion implantation is recrystallized by solid-phase epitaxial regrowth during FLA.     

Vibrational spectroscopy of InAs and AlAs quantum dot structures

In this paper we present an experimental comparative study of InAs/AlAs periodical structures with InAs and AlAs quantum dots (QDs) by means of infrared and Raman spectroscopies. The first observation of optical phonons localized in InAs and AlAs QDs using infrared spectroscopy is demonstrated. Confined optical phonon frequencies of the QDs measured by means of Raman scattering are compared with those deduced from the analysis of infrared spectra performed in the framework of the dielectric function approximation.     

EFFECT OF DOPANT ON THE UNIFORMITY OF InAs SELF-ORGANIZED QUANTUM DOTS

Low-temperature photoluminescence studies have been performed on Si-doped and Bedoped self-organized InAs/GaAs quantum dot(QD) samples to investigate the effect of doping. When Si or Be is doped into the sample,a remarkable decrease in line-width is observed. We relate this phenomenon to a model that takes the Si or Be atoms as the nucleation centers for the formation of QDs. When Si or Be is doped, more smalll uniform quantum dots are formed. The result will be of significance for the application of self-organized InAs quantum dots in semiconductor devices.     

Numerical simulation of a coupling effect on electronic states in quantum dots

Lasers operating at 1.3 μm have attracted considerable attention owing to their potential to provide efficient light sources for next-generation high-speed communication systems. InAs/GaAs quantum dots (QDs) were pointed out as a reliable low-cost way to attain this goal. However, due to the lattice mismatch, the accumulation of strain by stacking the QDs can cause dislocations that significantly degrade the performance of the lasers. In order to reduce this strain, a promising method is the use of InAs QDs embedded in InGaAs layers. The capping of the QD layer with InGaAs is able to tune the emission toward longer and controllable wave-lengths between 1.1 and 1.5 μm. In this work, using the effective-mass envelope-function theory, we investigated theoretically the optical properties of coupled InAs/GaAs strained QDs based structures emitting around 1.33 μm. The calculation was performed by the resolution of the 3D Schrödinger equation. The energy levels of confined carriers and the optical transition energy have been investigated. The oscillator strengths of this transition have been studied with and without taking into account the strain effect in the calculations. The information derived from the present study shows that the InGaAs capping layer may have profound consequences as regards the performance of an InAs/GaAs QD based laser. Based on the present results, we hope that the present work make a contribution to experimental studies of InAs/GaAs QD based structures, namely the optoelectronic applications concerning infrared and mid-infrared spectral regions as well as the solar cells.