Thermal Analysis of InAs/AlSb Short Wavelength Mid-IR Quantum Cascade Lasers

We present the effects of hetero-interfaces and major key parameters on the thermal behaviors and performance of short wavelength mid-IR InAs/AlSb quantum cascade lasers （QCLs）. We use a finite element method （FEM） with commercial software, ANSYS, to simulate the heat dissipation in QCLs in cw operation mode with an epilayer-down mounting package. The thermal performance is characterized by the temperature increase AT （self-heating effect） between the active region of QCLs and the heatsink. Results show that （1） the self-heating effects of InAs/AlSb QCLs are much less than those in AlInAs/GaInAs Q, CLs, （2） narrower ridges lead to significantly cooler active regions of InAs/AlSb QCLs due to poor heat transport in the cross-plane direction （across interfaces） and that most of the heat flows out of the active region in the lateral direction, and （3） the cavity length of the laser has little influence on the self-beating effect of the device, but the long cavity reduces mirror loss and threshold current density.     

Unidirectionally Emitting Quantum Cascade Microcavity Lasers with Patterned Contacts

We investigate unidirectionally emitting quantum cascade microcavity lasers with semicircle-patterned top contacts. We employ novel patterned top contacts while fabricating notched ellipse-shaped cavity lasers. We study experimentally the microcavity-structure-based quantum cascade (QC) laser material with a long infrared wavelength of ~10 μm. Then we characterize microcavity lasers with patterned contacts and compare them with nonpatterned ones and observe a lower operating injection threshold current as a consequence of this relatively straightforward technique, with the unidirectional emission feature being kept. We obtain a maximum light output peak power of 16 mW with unidirectional emission at a far-field divergence angle of ~7° at a full width of half maximum, while the patterned device shows low threshold even in the microcavity laser with a size of 150 μm. Furthermore, we also carry out a reliability test of the QC microcavity lasers with semicircle-patterned top contacts, and the testing results show no sudden failure or severe light-output-power drop during an operating time of thousand hours.     

Spectral Dynamics of Quantum Cascade Lasers Generating Frequency Combs in the Long-Wavelength Infrared Range

Technical Physics - We have studied the spectral and dynamic characteristics of quantum cascade lasers emitting in the long-wavelength infrared range. It is shown that lasers with a short cavity...     

1550 nm单模光纤中的量子密钥分配

从实验中实现了红外波段的远程量子密钥分配。系统采用双不等臂M-Z干涉仪相位编码方式,工作波长为1550nm。通过分析量子密钥分配系统传输距离与误码率之间相互关系,给出了理论上理想不等臂M-Z系统与实际系统的最低误码率与传输距离间的关系,以及系统实测传输距离与误码率的关系。实验结果显示,本密钥分配系统已非常接近理想实验系统的性能。     

Pulse Wavelength Scan of Room-Temperature Mid-Infrared Distributed Feedback Quantum Cascade Lasers for N2O Gas Detection

The tunable diode laser absorption spectroscopy under a pulse wavelength scan scheme is adapted to home-made room-temperature mid-infrared distributed feedback quantum cascade lasers; and identification of N2O spectral fingerprint is demonstrated experimentally. By driving the laser at 800ns pulse duration, a wave number tuning of about 1.6cm^-1 is produced, which make both 1289.04cm^-1 and 1289.86cm^-1 absorption fingerprints of N2O gas to be definitely assigned. The measured relative absorption intensity is consistent with the HITRAN data precisely.     

Radiation Temperature Scaling Law for Gold Hohlraum Heated with Lasers at 0.35 mm Wavelength

We have carried out the hohlraum experiments about radiation temperature scaling on the Shenguang-Ⅱ （SG- Ⅱ） laser facility with eight laser beams of 0.35#m, pulse duration of about 1.0ns and total energy of 2000J. The reradiated x-ray flux through the laser entrance hole was measured using a soft x-ray spectrometer. The measured peak radiation temperature was 170eV for the standard hohlraum and 150 eV for the 1.5-scaled one. We have derived the radiation temperature scaling law, in which the laser hohlraum coupling efficiency is included. With an appropriate coupling efficiency, the coincidences between experimental and scaling hohlraum radiation temperatures are rather good.     

在高于253 K温度下的1550 nm波长单光子探测实验

介绍了在高于253 K的温度下,实现红外单光子探测的实验.选用拉通电压较高的雪崩光电二极管（APD）,设计制作了非线性限流技术保护高温工作的APD,利用半导体热电制冷器,在256.8K的温度下,实现了1550 nm波段的单光子探测实验.单光子探测的暗记数率为3.13×10－5 ns,在220 kHz/s的单光子脉冲速率下,探测效率为2.08%.     

The Self-Heating Effect of Quantum Cascade Lasers Based on a Spectroscopic Method

We investigate the self-heating effect of mid-infrared quantum cascade lasers by using a direct-based pulse injecting current and spectroscopy method. Based on the characterization system, the thermal characteristics of gas source MBE grown 8.4μm InP-based GalnAs/AIInAs DFB-QCLs are evaluated. The method and characterization system are also useful in evaluating the thermal characteristics of other types of mid-infrared diode lasers.     

Low Threshold Distributed Feedback Quantum Cascade Lasers with Widely Spaced Emission Wavelengths

We report lasing properties of distributed feedback quantum cascade lasers （DFB QCLs） including a doublephonon-resonance active region, at wavelength of about 8.4 μm. A broad gain spectrum is generated due to the coupling between the lower laser level in the active region and the levels in the injector, and is demonstrated by the lasing spectrum of the corresponding Fabry-Perot QCLs whose width is 0.5 μm at 1.5 times of the threshold current. As a result, the DFB QCLs employing different grating periods exhibit a wavelength span of 0.18μm at room temperature and total wavelength coverage of 0.28μm at various heat sink temperatures. A high side mode suppression ratio of about 30dB and a low threshold current density of 1.78kA/cm^2 are achieved as the lasers operate at room temperature in pulsed mode.     

Magnon BEC at Room Temperature and Its Spatio-Temporal Dynamics

Journal of Experimental and Theoretical Physics - Recent advances in the studies of magnon gases have opened new horizons for the investigation of room-temperature macroscopic coherent states and...     

一种基于室温工作的量子点光电探测器的微光读出和应用研究

针对量子点光电探测器线列进行微光检测研究,量子点探测器采用AlAs/GaAs/AlAs双势垒结构,GaAs宽阱中分别有一个InAs量子点(QDs)和In_0.15Ga_0.85As量子阱(QW),建立一个简单的器件模型进行分析。常温下,在632.8 nm He-Ne激光照射下,当光功率为 0.01 pW时,器件偏压-0.5 V,积分时间80.2 μs,电压响应率达到7.0×1011 V·W-1,具有非常高的灵敏度,这种光电探测器在300 K温度下可以探测光功率小于10-14 W极弱光。以这种量子点光电探测器为核心研制的高灵敏度光谱仪和分子超光谱系统结合对生物组织样本进行检测,研制了一种图谱相互验证,互为校正的生物组织光谱测量系统。     

Quantum Discord in Nuclear Magnetic Resonance Systems at Room Temperature

We review the theoretical and the experimental researches aimed at quantifying or identifying quantum correlations in liquid-state nuclear magnetic resonance (NMR) systems at room temperature. We first overview, at the formal level, a method to determine the quantum discord and its classical counterpart in systems described by a deviation matrix. Next, we describe an experimental implementation of that method. Previous theoretical analysis of quantum discord decoherence had predicted the time dependence of the discord to change suddenly under the influence of phase noise. The experiment attests to the robustness of the effect, sufficient to confirm the theoretical prediction even under the additional influence of a thermal environment. Finally, we discuss an observable witness for the quantumness of correlations in two-qubit systems and its first NMR implementation. Should the nature, not the amount, of the correlation be under scrutiny, the witness offers the most attractive alternative.     

Phosphorescence of Oxygen Excited at a Wavelength of 765 nm

Optics and Spectroscopy - The phosphorescence of oxygen in the liquid phase and in tetrachloromethane solution is studied under direct optical excitation by a light-emitting diode array at a...     

吸收型双稳半导体激光器的起振波长

从双稳半导体激光器上跳阈值处的谐振波长是所需阈值电流最低的波长这个物理事实出发，利用双稳半导体激光器的速率方程组，本文对双稳半导体激光器上跳阈值处的谐振波长进行了研究。文中还就一些器件参量对双稳半导体激光器上跳阈值处谐振滤长的影响进行了讨论。     

飞秒激光在可饱和吸收体中的动力学特性

从激光动力学的自洽理论出发,推导出适用于含有可饱和吸收体的激光系统动力学方程组,研究了激光振荡的稳定性与系统参数的依赖关系,包括激励强度参数、饱和系数和能级寿命,并讨论了满足激光振荡稳定性的条件下B类激光的弛豫振荡特性。结果表明,增大激励强度与饱和系数有利于系统形成稳定的振荡输出,而且当激励强度超过一定阈值时,B类激光会产生弛豫振荡行为。     

Dynamics of Two-Photon Lasers with

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影响AlGaN/GaN量子级联激光器性能的因素研究

在已有理论基础之上,采用严格的计算方法对激光器实现太赫兹(THz)波的辐射进行了可能性分析。利用传递矩阵法,通过Matlab软件计算了基于AlGaN/GaN材料体系的三能级量子级联激光器导带子能级与电子波函数的分布,详细分析了由该材料特有的极化效应所产生的极化场,得出了在近共振条件下偶极跃迁元、外加电场、垒层Al组分及导带子能级能级差之间的关系,并研究了它们对激光器性能的影响。分析结果表明,实现受激辐射的条件非常严格,Al组分取0.15或0.16时较为适宜,同时外加电场需大于63kV/cm,但不能过大,这样才能满足近共振条件,实现粒子数反转达到太赫兹量子级联激射。在Al组分为0.15,外加电场为69.0kV/cm时激光器的偶极跃迁元最大,表明跃迁几率也最大,对激光器的性能有利,可以为量子级联激光器构造较好的有源区。     

球形微粒样品室温永久光谱烧孔的动力学过程及多重性研究

利用球粒表面形态共振，实现室温下的永久光谱烧孔，建立理论模型对动力学过程进行分析，据此对实验结果进行拟合，得到有效成孔速率等参数；并对烧孔的多重性进行研究，将这些结果应用于室温频域光信息存贮将有较好的前景。