2.9THz束缚态向连续态跃迁量子级联激光器研制

采用气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材料, 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. 测量了激光器的发射光谱和功率-电流-电压关系曲线, 研究了器件的激光特性. 器件激射频率约2.95 THz, 脉冲模式下, 最高工作温度为67 K. 连续波模式下, 阈值电流密度最低为230 A/cm², 最大光输出功率1.2 mW, 最高工作温度为30 K. 关键词： 太赫兹 量子级联激光器 分子束外延 波导     

半绝缘等离子体波导太赫兹量子级联激光器工艺研究

采用气态源分子束外延设备生长了GaAs/AlGaAs束缚态到连续态跃迁结构的太赫兹（THz）量子级联激光器（QCL）有源区结构,研究了半绝缘等离子体波导THz QCL的器件工艺,采用远红外傅里叶变换光谱仪以及探测器测量了器件的电光特性.器件激射频率为32 THz,10 K下的阈值电流密度为275 A/cm². 关键词： 太赫兹 量子级联激光器 波导 器件工艺     

三阶分布反馈太赫兹量子级联激光器的远场分布特性

研究了三阶分布反馈太赫兹量子级联激光器的设计、制作并分析了其纵模和横模特性.通过建立波导结构模型,利用有限元方法模拟激光器波导结构内的三维模场分布,通过本征模的损耗分析器件的纵模模式选择机理.同时,由本征模的近场通过近-远场傅里叶变换求得激光器的远场分布.采用半导体工艺制作了4.3 THz双面金属波导三阶分布反馈量子级联激光器,测量了不同器件的发射谱和远场光束质量,远场发散角为12?×13?,实验结果和理论模拟符合.     

太赫兹量子级联激光器光频梳射频传输

针对太赫兹量子级联激光器光频梳射频信号提取与传输存在的阻抗不匹配问题,设计并提出了一种输入阻抗为20Ω、输出阻抗为50Ω的渐变微带线结构,研究了该结构的准TEM模电场分布,并根据S参数建立了相应的LC等效电路模型分析其物理机理。实验中,将渐变微带线结构应用于太赫兹量子级联激光器光频梳射频信号提取与测试,以验证渐变微带线传输射频信号效果,成功测量得到太赫兹量子级联激光器重复频率,其线宽为3.7 kHz,信噪比达到60 dB,在注入电流为700～900 mA范围内重复频率表现为稳定的单模信号,测量得到的最大保持和幅度艾伦方差结果同样表现出重复频率的稳定性。实验结果表明,所设计的渐变微带线具有良好的阻抗匹配效果,能够实现对太赫兹量子级联激光器光频梳射频信号稳定的提取和传输。     

锥形太赫兹量子级联激光器输出功率与光束特性研究

针对锥形太赫兹量子级联激光器, 利用有限差分波束传播法和速率方程法, 建立了准三维的太赫兹有源器件仿真模型, 能够对具有轴向非线性波导结构的激光器进行模拟. 利用此模型, 研究了锥角大小对激光器输出光功率及光束质量的影响. 仿真结果表明, 考虑到器件之间的光耦合效率, 为了达到最大的有效输出光功率, 锥形太赫兹量子级联激光器的锥角存在一个最优值.     

太赫兹半导体激光光频梳研究进展

光频梳由一系列等间距、高稳定性的频率线组成.由于具有超高频率稳定性和超低相位噪声,光频梳在精密光谱测量、成像、通信等领域具有重要应用.在太赫兹波段,基于半导体的电抽运太赫兹量子级联激光器具有大功率输出、宽频率覆盖范围等特点,是产生太赫兹光频梳的理想载体.本文主要介绍基于太赫兹半导体量子级联激光器光频梳的研究进展,详细列举了自由运行、主动稳频和被动稳频模式下产生光频梳的方法.双光梳光谱可以克服传统太赫兹光谱仪需要机械扫描系统而难以实现实时光谱检测的难题,是光频梳应用的主要方向.在光频梳基础之上,本文还介绍了采用两个太赫兹量子级联激光器产生双光梳的方法和应用.     

基于掩埋光栅一级分布反馈结构的太赫兹量子级联激光器

结合理论和实验研究了掩埋光栅一级分布反馈太赫兹量子级联激光器中的模式竞争和功率特性。理论计算得到掩埋光栅腐蚀深度与两个带边模式的波导损耗、光学限制因子、辐射损耗以及辐射效率的关系。理论计算表明,掩埋光栅分布反馈结构可以通过改变腐蚀深度,保证激光器稳定单模工作在高频带边模式的同时,调节激光器的阈值增益以及辐射效率。实验和测试结果表明,激光器辐射波长和掩埋光栅的周期成正比,激光器可以在整个动力学范围内稳定单模工作。单模激光器的波长范围可覆盖86.2~91.7μm的范围,边模抑制比可达25 dB,最大输出功率为9.1 mW。该工作有助于高性能单模太赫兹激光器及锁相耦合激光器阵列的研制。     

Si/SiGe量子级联激光器研究进展

Si／SiGe量子级联激光器是一种新型的带内跃迁的红外光源，突破了Si基材料间接带隙特性对光跃迁的限制。Si/SiGe量子级联激光器的开发将为实现太赫兹有源器件的硅基集成产生深远影响。文章介绍了Si/SiGe量子级联激光器的工作原理，以及这类激光器在能带设计、材料生长和波导制作方面的最新进展。     

大口径柔性介质金属膜太赫兹波导的制作与特性

基于介质/金属膜结构空芯波导的原理,制作了用于太赫兹波传输的大口径柔性介质/金属膜波导。针对大口径的特点,设计改良了液相镀膜法并制作了具有不同介质膜厚的柔韧波导。对制作波导的介质膜厚和损耗谱等进行了理论分析和实验验证。采用发射频率为2.5 THz的量子级联激光器,对介质/金属膜结构太赫兹空芯波导的传输损耗、弯曲附加损耗以及光斑能量分布特性等进行了实验研究。结果表明,传输损耗及弯曲附加损耗均随介质膜厚的增加而减小,光斑能量则随介质膜厚的增加更加集中于低阶传输模式。     

基于太赫兹量子阱探测器的太赫兹量子级联激光器发射谱研究

采用一个光谱匹配的太赫兹(THz)量子阱探测器(QWP)研究了一激射频率约为41 THz的THz量子级联激光器(QCL)在不同驱动电流下的发射谱,分析了测量得到的发射谱谱型和谱峰位置,根据测量的发射谱估算了太赫兹量子级联激光器发射功率随驱动电流变化的情况,从而得到了THz QCL激射的电流密度范围及其阈值电流密度.文中还研究了THz QWP在不同温度下对THz QCL 激光辐射的响应特性.研究结果表明,THz QWP在表征THz QCL的发射谱方面是一种很好的探测器,并有望成为未来THz通信中的接收装置. 关键词： 太赫兹量子阱探测器 太赫兹量子级联激光器 太赫兹通信 Fourier变换红外光谱     

Short Terahertz Pulse Generation from a Dispersion Compensated Modelocked Semiconductor Laser

Dispersion compensation is vital for the generation of ultrashort and single cycle pulses from modelocked lasers across the electromagnetic spectrum. It is typically based on addition of an extra dispersive element to the laser cavity that introduces a chromatic dispersion opposite to that of the gain medium. To date, however, no dispersion compensation schemes have been successfully applied to terahertz (THz) quantum cascade lasers for short and stable pulse generation in the THz range. In this work, a monolithic on‐chip compensation scheme is realized for a modelocked QCL, permitting THz pulses to be considerably shortened from 16ps to 4ps. This is based on the realization of a small coupled cavity resonator that acts as an ‘off resonance’ Gires‐Tournois interferometer (GTI), permitting large THz spectral bandwidths to be compensated. This novel application of a GTI opens up a direct and simple route to sub‐picosecond and single cycle pulses in the THz range from a compact semiconductor source.     

Phase-locking of a 2.5 THz quantum cascade laser to a frequency comb using a GaAs photomixer

We report the heterodyne detection and phase locking of a 2.5?THz quantum cascade laser (QCL) using a terahertz frequency comb generated in a GaAs photomixer using a femtosecond fiber laser. With 10?mW emitted by the QCL, the phase-locked signal at the intermediate frequency yields 80?dB of signal-to-noise ratio in a bandwidth of 1?Hz.     

Experimental study of air-core dielectric tube at terahertz frequencies

In this paper, an experimental study of air-core dielectric tube waveguide is proposed at terahertz frequencies. By using the THz time domain measure system, the terahertz dispersion characteristics, loss characteristic and energy focusing characteristic of air-core single-layer and dual-layer dielectric tube are obtained. The results show that this type of air-core dielectric tube can realize low dispersion characteristics. Due to the difference of refractive index between two dielectric materials, stronger energy focusing can be achieved in air-core dual-layer dielectric tube. After the coupling of the THz pulse using the dual-layer dielectric tube waveguide, the THz pulse increased 2.4 times compared with the single-layer dielectric tube waveguide at 1.5 THz.     

Integrated injection seeded terahertz source and amplifier for time-domain spectroscopy

We used a terahertz (THz) quantum cascade laser (QCL) as an integrated injection seeded source and amplifier for THz time-domain spectroscopy. A THz input pulse is generated inside a QCL by illuminating the laser facet with a near-IR pulse from a femtosecond laser and amplified using gain switching. The THz output from the QCL is found to saturate upon increasing the amplitude of the THz input power, which indicates that the QCL is operating in an injection seeded regime.     

Material growth and device fabrication of terahertz quantum-cascade laser based on bound-to-continuum structure

The terahertz quantum-cascade laser （THz QCL） based on bound-to-continuum structure is demonstrated. The X-ray diffraction measurement of the material shows a high crystalline quality of the active region. A THz QCL device was fabricated with semi-insulating surface-plasmon waveguide. The test device is lasing at about 3 THz and operating up to 60 K. It shows a single frequency property under different drive currents and temperatures. At 9 K, the maximum output power is greater than 2 mW with a threshold current density of 159 A/cm2.     

Real-time reflection imaging with terahertz camera and quantum-cascade laser

A real-time reflection imaging employing a terahertz （THz） camera as the imager and a 3.9 THz quantum- cascade laser （QCL） as the light source is demonstrated. The imaging light is collected and guided by only one off-axis parabolic mirror. The imaging distance is about 1 m. THz images of a coin and a knife are aacquired and analyzed. An actual soatial resolution with a value of about 0.33 mm is achieved.     

Terahertz imaging through self-mixing in a quantum cascade laser

We demonstrate terahertz (THz) frequency imaging using a single quantum cascade laser (QCL) device for both generation and sensing of THz radiation. Detection is achieved by utilizing the effect of self-mixing in the THz QCL, and, specifically, by monitoring perturbations to the voltage across the QCL, induced by light reflected from an external object back into the laser cavity. Self-mixing imaging offers high sensitivity, a potentially fast response, and a simple, compact optical design, and we show that it can be used to obtain high-resolution reflection images of exemplar structures.     

基于太赫兹量子级联激光器的无线信号传输的实现

文章采用连续波激射的太赫兹量子级联激光器(THz QCL) 为发射端、光谱匹配的THz量子阱探测器(THz QWP) 为接收端, 搭建了基于THz波的无线传输演示系统. 测量并分析了该演示系统的传输带宽. 采用搭建的无线传输系统演示了基于4.13 THz电磁波的图片文件的无线传输过程, 得到了与源文件一致的结果, 验证了采用THz QCL和THz QWP进行THz信号无线传输的可行性.最后, 分析了演示系统的传输速率, 给出了提高系统传输速率的方法.