室温 THz-QCL 源

面向下一代 ICT、非破坏性检测/分析和天文学的纳米技术

概述

太赫兹 (THz) 光谱范围在通信、非破坏性成像、光谱学和生物工程等众多领域具有相当大的应用潜力。阻碍该技术广泛商业化部署的一个主要障碍是缺乏在太赫兹范围内工作的紧凑且可批量生产的高性能半导体源。如图 1 所示，在低频侧（来自电子器件），谐振隧道二极管 (RTD) 振荡器在室温下工作。另一方面，在高频侧（来自光学装置），已报告有太赫兹量子级联激光器 (THz-QCL)；然而，它们需要低温冷却。

图 1：室温半导体 THz 源（输出功率与频率）

量子级联激光器 (QCL) 是半导体发光装置（图 2(a)）。该光源是通过对分子束外延或金属有机气相外延晶体生长技术生长的半导体异质结构中的电子波函数进行工程设计而创造的最知名器件之一。与基于带间跃迁的器件不同，QCL 的电学和光学特性（如光学跃迁能量和偶极矩、上下激光态寿命和电子传输）由其异质结构设计决定。工作原理如图 2(b) 所示。在过去的二十年中，QCL 已成为中红外和太赫兹区域最具吸引力的半导体源。然而，THz QCL 仍需要低温冷却才能运行。

图 2(a) 量子级联激光器器件

(b) QCL 的工作原理

从 QCL 生成 THz 的另一种方法是基于双波长中红外 QCL 中的腔内差频生成 (DFG)。这些器件称为 THz DFG-QCL，使用经过设计的中红外 QCL 有源区，可表现出巨大的子带间非线性磁化率 χ⁽²⁾，从而实现高效的 THz DFG 过程（图 3）。施加偏置电流时，THz DFG-QCL 通过器件有源区中的腔内非线性混频过程产生两个中红外泵浦频率，以及对应于中红外泵浦频率差的太赫兹频率。DFG-QCL 有源区的光学非线性不需要跨 THz 跃迁的粒子数反转。因此，与 THz QCL 不同，THz DFG-QCL 可在室温下工作。THz DFG-QCL 是目前唯一可在室温下工作的电泵浦、单片、可批量生产的半导体源。

图 3：基于非线性光学效应的 THz QCL 源的工作原理概念图

在我们集团中，通过使用我们最初的概念“Anticross DAU 有源区（图 4(a)）”，我们在室温下实现了 mW 级输出功率。THz 输出功率可通过室温 THz 热电探测器检测。此外，我们还基于 DAU 有源区获得了跨越一个倍频程的超宽带太赫兹发射光谱（图 4(b)），于是，我们成功地展示了使用这些太赫兹源的太赫兹成像。

图 4 (a) AnticrossDAU 结构

(b) 室温宽带太赫兹非线性 QCL 器件的典型特性

图 5 使用宽带 THz-QCL 源的光谱成像（聚乙烯、D-组氨酸、DL-组氨酸，转载自参考文献 1）

未来用途

太赫兹频率范围对于许多应用都非常重要，例如成像、化学/生物传感、外差检测和光谱仪。在 ICT 领域，超宽带无线通信有望用于短距离用途，而长距离传输由于强吸水性而难以实现。
在非破坏性检测和分析领域，太赫兹频率范围辐射已用于展示光学频率下不透明物体的成像。太赫兹用途有许多，包括化学物质筛选、工业材料和历史艺术品的非破坏性成像。通过构建使用太赫兹非线性 QCL 的紧凑型成像系统，未来将对太赫兹成像技术进行大量研究。

在天文学领域，太赫兹频率信号非常重要，因为在此频率范围内可以探测到星际气体和灰尘。通过星际气体的精细结构线，可以研究恒星的形成过程。出于这些目的，天文接收器需要紧凑的本地振荡器。由于太赫兹非线性 QCL 源可以产生单频太赫兹信号，因此可以将其用作 LO 来分析来自太空的太赫兹波信号。

参考资料

A. Nakanishi, S. Hayashi, H. Satozono, and K. Fujita, “Spectroscopic Imaging with an Ultra-Broadband (1–4 THz) Compact Terahertz Difference-Frequency Generation Source,” Electronics, Vol. 10, pp. 336, 2021.
L. Consolino, M. Nafa, M. De Regis, F. Cappelli, ... and K. Fujita, “Direct Observation of Terahertz Frequency Comb Generation in Difference-Frequency Quantum Cascade Lasers,” Applied Sciences, Vol. 11, no.4 pp. 1416, 2021.
Shohei Hayashi, Akio Ito, Masahiro Hitaka, and Kazuue Fujita, “Room temperature, single-mode 1.0 THz semiconductor source based on long-wavelength infrared quantum-cascade laser,” Applied Physics Express Vol. 13, pp. 112001, 2020.
Atsushi Nakanishi, Hiroshi Satozono, and Kazuue Fujita, “Detection of single human hairs with a terahertz nonlinear quantum cascade laser,” Applied Optics Vol. 59, pp. 9169-9173, 2020.
Atsushi Nakanishi, Shohei Hayashi, Hiroshi Satozono, and Kazuue Fujita, “Temperature-Insensitive Imaging Properties of a Broadband Terahertz Nonlinear Quantum Cascade Laser,” Applied Sciences Vol. 10, pp. 5926, 2020.
Kazuue Fujita, Shohei Hayashi, Atsushi Nakanishi, Akio Ito, Masahiro Hitaka, and Tatsuo Dougakiuchi, "Sub-terahertz and terahertz generation in long-wavelength quantum cascade lasers," Nanophotonics Vol. 8, pp. 2235-2241, 2019.
Masahiro Hitaka, Tatsuo Dougakiuchi, Akio Ito, Kazuue Fujita, Tadataka Edamura, "Stacked quantum cascade laser and detector structure for a monolithic mid-infrared sensing device," Applied Physics Letters Vol. 115, pp. 161102, 2019.
Atsushi Nakanishi, Kazuue Fujita, Kazuki Horita, and Hironori Takahashi, "Terahertz imaging with room-temperature terahertz difference-frequency quantum-cascade laser sources," Optics express Vol. 27, pp.1884-1893, 2019.
Jae Hyun Kim, Seungyong Jung, Yifan Jiang, Kazuue Fujita, Masahiro Hitaka, Akio Ito, Tadataka Edamura, and Mikhail A. Belkin, "Double-metal waveguide terahertz difference-frequency generation quantum cascade lasers with surface grating outcouplers," Applied Physics Letters Vol. 113, pp.161102, 2018.
Kazuue Fujita, Seungyong Jung, Yifan Jiang, Jae Hyun Kim, Atsushi Nakanishi, Akio Ito, Masahiro Hitaka, Tadataka Edamura, and Mikhail A. Belkin, "Recent progress in terahertz difference-frequency quantum cascade laser sources (Invited Review Article)," Nanophotonics Vol. 7, pp.1795-1817, 2018.
Kazuue Fujita, Akio Ito, Masahiro Hitaka, Tatsuo Dougakiuchi, and Tadataka Edamura. "Development of THz light sources based on QCL technology." In Quantum Sensing and Nano Electronics and Photonics XV, Vol. 10540, pp. 105401J. International Society for Optics and Photonics, 2018.
Luigi Consolino, Seungyong Jung, Annamaria Campa, Michele De Regis, Shovon Pal, Jae Hyun Kim, Kazuue Fujita et al., "Spectral purity and tunability of terahertz quantum cascade laser sources based on intracavity difference-frequency generation," Science advances Vol. 3, pp. e1603317, 2017.
Kazuue Fujita, Akio Ito, Masahiro Hitaka, Tatsuo Dougakiuchi, and Tadataka Edamura, "Low-threshold room-temperature continuous-wave operation of a terahertz difference-frequency quantum cascade laser source," Applied Physics Express Vol. 10, pp. 082102, 2017.
Tatsuo Dougakiuchi, Kazuue Fujita, Toru Hirohata, Akio Ito, Masahiro Hitaka, and Tadataka Edamura, "High photoresponse in room temperature quantum cascade detector based on coupled quantum well design," Applied Physics Letters Vol. 109, pp. 261107, 2016.
Kazuue Fujita, Masahiro Hitaka, Akio Ito, Masamichi Yamanishi, Tatsuo Dougakiuchi, and Tadataka Edamura, "Ultra-broadband room-temperature terahertz quantum cascade laser sources based on difference frequency generation," Optics express Vol. 24, pp. 16357-16365, 2016.
Kazuue Fujita, Masahiro Hitaka, Akio Ito, Tadataka Edamura, Masamichi Yamanishi, Seungyong Jung, and Mikhail A. Belkin, "Terahertz generation in mid-infrared quantum cascade lasers with a dual-upper-state active region," Applied Physics Letters Vol. 106, pp. 251104, 2015.
Masamichi Yamanishi, Tooru Hirohata, Syohei Hayashi, Kazuue Fujita, and Kazunori Tanaka, "Electrical flicker-noise generated by filling and emptying of impurity states in injectors of quantum-cascade lasers," Journal of Applied Physics Vol. 116, pp. 183106, 2014.
Tatsuo Dougakiuchi, Kazuue Fujita, Atsushi Sugiyama, Akio Ito, Naota Akikusa, and Tadataka Edamura, "Broadband tuning of continuous wave quantum cascade lasers in long wavelength (> 10μm) range," Optics express Vol. 22, pp. 19930-19935, 2014.
Bo Meng, Masamichi Yamanishi, Christian Pflügl, Kazuue Fujita, Federico Capasso, and Qi Jie Wang, "Investigation of tunable single-mode quantum cascade lasers via surface-acoustic-wave modulation," IEEE Journal of Quantum Electronics Vol. 49, pp. 1053-1061, 2013.
Romain Blanchard, Tobias S. Mansuripur, Burc G€okden, Nanfang Yu, Mikhail Kats, Patrice Genevet, Kazuue Fujita, Tadataka Edamura, Masamichi Yamanishi, and Federico Capasso, "High-power low-divergence tapered quantum cascade lasers with plasmonic collimators,"Appl. 杂志 Lett., Vol. 102, pp.191114 -1-191114 -5, 2013.
Pietro Malara, Romain Blanchard, Tobias S. Mansuripur, Aleksander K. Wojcik, Alexey Belyanin, Kazuue Fujita, Tadataka Edamura, Shinichi Furuta, Masamichi Yamanishi, Paolo de Natale, and Federico Capasso, "External ring-cavity quantum cascade lasers," Appl. 杂志 Lett., Vol. 102, No.14, 141105-1-141105-5, 2013.
Kazuue Fujita, Masamichi Yamanishi, Shinichi Furuta, Atsushi Sugiyama, and Tadataka Edamura, "Extremely temperature-insensitive continuous-wave quantum cascade lasers," Appl. 杂志 Lett., Vol.101, No.18, pp.181111-1-181111-4, 2012.
Kazuue Fujita, Masamichi Yamanishi, Shinichi Furuta, Kazunori Tanaka, Tadataka Edamura, Tillmann Kubis, and Gerhard Klimeck," Indirectly pumped 3.7 THz InGaAs/InAlAs quantum-cascade lasers grown by metal-organic vapor-phase epitaxy," Optics Express, Vol. 20, pp.20647-20658, 2012.
Tatsuo Dougakiuchi, Kazuue Fujita, Naota Akikusa, Atsushi Sugiyama,Tadataka Edamura, and Masamichi Yamanishi,"Broadband Tuning of External Cavity Dual-Upper-State Quantum-Cascade Lasers in Continuous Wave Operation," Applied Physics Express, Vol. 4, pp. 102101-1-102101-3, 2011.
Kazuue Fujita, Shinichi Furuta, Atsushi Sugiyama, Takahide Ochiai, Akio Ito, Tatsuo Dougakiuchi, Tadataka Edamura, and Masamichi Yamanishi, “High-temperature quantum cascade lasers with wide electroluminescence (~600 cm-1), operationg in continuous wave above 100 oC,” Applied Physics Letters, Vol. 98, pp.231102-1-231102-3, 2011.
Kazuue Fujita, Shinichi Furuta, Tatsuo Dougakiuchi, Atsushi Sugiyama, Tadataka Edamura, and Masamichi Yamanishi, “Extremely broad-gain (Δλ/λ0~0.4), temperature-insensitive (T0~510K) quantum cascade lasers,” Optics Express,　Vo. 19, pp.2694－2701, 2011.
Kazuue Fujita, Masamichi Yamanishi, Tadataka Edamura, Atsushi Sugiyama, and Shinichi Furuta, “Extremely high T0-values (~450 K) of long-wavelength (~15 μm), low-threshold-current-density quantum-cascade lasers based on the indirect pump scheme,” Applied Physics Letters, Vol. 97, pp.201109-1－201109-3, 2010.
Kazuue Fujita, Tadataka Edamura, Shinichi Furuta, and Masamichi Yamanishi, “High-performance, homogeneous broad-gain quantum cascade lasers based on dual-upper-state design,” Applied Physics Letters, Vol. 96, pp.241107-1－241107-3, 2010.
Kazuue Fujita, Shinich Furuta, Atsushi Sugiyama, Takahide Ochiai, Tadataka Edamura, Naota Akikusa, Masamichi Yamanishi and Hirofumi Kan, “High-Performanceλ∼ 8.6 μm Quantum Cascade Lasers With Single Phonon-Continuum Depopulation Structures,” IEEE Journal Of Quantum Electronics, Vol. 46, pp.683－688, 2010.
M. Ishihara, T. Morimoto, S. Furuta, K. Kasahara, N. Akikusa, K. Fujita, and T. Edamura, "Linewidth enhancement factor of quantum cascade lasers with single phonon resonance-continuum depopulation structure on Peltier cooler," Electronics letters Vol. 45, pp. 1168-1169, 2009.
Kazuue Fujita, Tadataka Edamura, Naota Akikusa, Atsushi Sugiyama, Takahide Ochiai, Shinichi Furuta, Akio Ito, Masamichi Yamanishi, and Hirofumi Kan, "Quantum cascade lasers based on single phonon-continuum depopulation structures," In Novel In-Plane Semiconductor Lasers VIII, Vol. 7230, p. 723016. International Society for Optics and Photonics, 2009.
Masamichi Yamanishi, Kazuue Fujita, Tadataka Edamura, and Hirofumi Kan, “Indirect pump scheme for quantum cascade lasers: dynamics of electron-transport and very high T0-values,” Optics Express, Vol. 16, pp.20748－20758, 2008.
Masamichi Yamanishi, Tadataka Edamura, Kazuue Fujita, Naota Akikusa, and Hirofumi Kan, "Theory of the intrinsic linewidth of quantum-cascade lasers: Hidden reason for the narrow linewidth and line-broadening by thermal photons," IEEE Journal of Quantum Electronics Vol. 44, 12-29, (2008).
K. Fujita, S. Furuta, A. Sugiyama, T. Ochiai, T. Edamura, N. Akikusa, M. Yamanishi, and H. Kan, “Room temperature, continuous-wave operation of quantum cascade lasers with single phonon resonance-continuum depopulation structures grown by metal organic vapor-phase epitaxy,” Applied Physics Letters, Vol. 91, pp.141121-1－141121-3, 2007.

室温 THz-QCL 源

面向下一代 ICT、非破坏性检测/分析和天文学的纳米技术

概述

未来用途

参考资料

如需更多信息，请联系我们。

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