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摘要: 太赫兹频率的相干声子在纳米尺度器件的探测和操控领域具有重要的应用价值。半导体超晶格声子激光器是实现太赫兹频率相干声子源稳定输出的重要途径。本文首先回顾了GHz到THz频率范围声学放大的多种方法,然后详细阐述了超晶格声子放大、超晶格声学布拉格镜的工作原理与设计方法以及声子激光器的阈值条件,同时总结了电抽运和光抽运结构器件的研究现状,最后简要讨论了亚太赫兹声子激光器在声-电子领域的应用。分析表明,这种能够产生强相干太赫兹声子的半导体超晶格声子激光器在纳米尺度器件的探测与成像等方面具有广阔的发展前景。Abstract: The coherent phonons at terahertz frequency have important applications in the field of detection and control of nanometer scale devices. Semiconductor superlattice phonon laser is an important way to realize the stable source of terahertz coherent phonon. Firstly, some methods about acoustic amplification in GHz-THz frequency range are reviewed. Next, the phonon amplification in superlattices, the working principles and design methods of superlattice acoustic Bragg reflectors and threshold of phonon laser are all elaborated. Then the research status on electrically pumped and optically pumped phonon lasers are summarized. Lastly, the applications for sub-terahertz phonon laser in the acoustic-electrons field are briefly discussed. The semiconductor superlattice phonon laser producing strong coherent phonons at terahertz frequency will have a much broader development prospect in multiple aspects, such as the detection and imaging of nanoscale devices.
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Key words:
- phonon laser /
- phononic crystal /
- semiconductor superlattic /
- laser ultrasonic
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图 1 GaAs/AlAs超晶格示意图; (b)零偏压下的电学能带结构示意图; (c)施加电场E后的能带结构示意图[33]
Figure 1. (a) Schematic diagram of GaAs/AlAs superlattice; (b) Schematic diagram of electronic band structure with zero applied bias; (c) Schematic diagram of band structure under applied bias electric field E
图 2 具有N个周期的周期性超晶格示意图[37]
Figure 2. Schematic diagram of periodic superlattice with N cycles
图 3 50周期GaAs/AlAs超晶格中折叠的声子色散[39]
Figure 3. Folded phonon dispersion for a 50-cycle GaAs/AlAs superlattice
图 4 (a)抽运-探测实验设置及(b)光抽运声子激光器样品的电结构示意图[53]
Figure 4. (a) Experiment arrangement for pump-probe measurement and (b) schematic diagram of optical pumped phonon laser sample
图 5 抽运-探测实验信号(插图中展示了440 GHz的声子振荡和傅里叶谱[53])
Figure 5. Signal of pump-probe measurement (440 GHz phonon oscillations and Fourier spectrum are shown in the insets)
图 6 在零偏压时(虚线)和有偏压诱导时(实线)的傅里叶谱[53]
Figure 6. Fourier spectrum at zero bias (dashed line) and bias-induced signal (solid line)
图 7 电抽运声子激光器的结构[39]
Figure 7. Structure diagram of an electrical pumped phonon laser
图 8 (a) θ=0°时测辐射热计的声子信号; (b)声子激光器的微分电导与斯塔克位移间的关系[39]
Figure 8. (a) Phonon signal of bolometers at θ=0°; (b) Differential conductance of phonon laser as a function of Stark shift
图 9 垂直腔面发射声子激光器的示意图[33]
Figure 9. Schematic diagram of vertical cavity surface-emitting phonon laser
图 10 2个测辐射热计上信号与抽运电压间的关系[33]
Figure 10. Time-integrated signal as a function of electrical pump voltage for two bolometers
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