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Homogeneous quantum cascade lasers operating as terahertz frequency combs over their entire operational regime
Nanophotonics ( IF 7.5 ) Pub Date : 2020-09-28 , DOI: 10.1515/nanoph-2020-0378
Alessandra Di Gaspare 1 , Leonardo Viti 1 , Harvey E. Beere 2 , David D. Ritchie 2 , Miriam S. Vitiello 1
Affiliation  

Abstract We report a homogeneous quantum cascade laser (QCL) emitting at terahertz (THz) frequencies, with a total spectral emission of about 0.6 THz, centered around 3.3 THz, a current density dynamic range J dr = 1.53, and a continuous wave output power of 7 mW. The analysis of the intermode beatnote unveils that the devised laser operates as an optical frequency comb (FC) synthesizer over the whole laser operational regime, with up to 36 optically active laser modes delivering ∼200 µW of optical power per optical mode, a power level unreached so far in any THz QCL FC. A stable and narrow single beatnote, reaching a minimum linewidth of about 500 Hz, is observed over a current density range of 240 A/cm2 and even across the negative differential resistance region. We further prove that the QCL FC can be injection locked with moderate radio frequency power at the intermode beatnote frequency, covering a locking range of 1.2 MHz. The demonstration of stable FC operation, in a QCL, over the full current density dynamic range, and without any external dispersion compensation mechanism, makes our proposed homogenous THz QCL an ideal tool for metrological applications requiring mode-hop electrical tunability and a tight control of the frequency and phase jitter.

中文翻译:

均质量子级联激光器在其整个工作状态下作为太赫兹频率梳工作

摘要 我们报告了一种以太赫兹 (THz) 频率发射的均匀量子级联激光器 (QCL),总光谱发射约为 0.6 THz,以 3.3 THz 为中心,电流密度动态范围 J dr = 1.53,连续波输出功率7 兆瓦。对模间拍音的分析表明,设计的激光器在整个激光器工作范围内作为光频梳 (FC) 合成器运行,具有多达 36 个光有源激光模式,每个光模式可提供约 200 µW 的光功率,这是一个功率水平迄今为止在任何 THz QCL FC 中都未达到。在 240 A/cm2 的电流密度范围内甚至在负微分电阻区域内观察到稳定且窄的单拍音,达到约 500 Hz 的最小线宽。我们进一步证明,QCL FC 可以在模式间拍音频率下以中等射频功率注入锁定,锁定范围为 1.2 MHz。在 QCL 中,在整个电流密度动态范围内,并且没有任何外部色散补偿机制的稳定 FC 操作的演示,使我们提出的同质 THz QCL 成为需要模式跳变电可调性和严格控制的计量应用的理想工具频率和相位抖动。
更新日期:2020-09-28
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