Recent progress in terahertz difference-frequency quantum cascade laser sources

Nanophotonics

article

Kazuue Fujita¹  Mikhail A. Belkin²  Seungyong Jung²  Yifan Jiang²  Jae Hyun Kim²  Atsushi Nakanishi¹  Akio Ito¹  Masahiro Hitaka¹  Tadataka Edamura¹ 

[1] Central Research Laboratory;Department of Electrical and Computer Engineering, The University of Texas at Austin

关键词: difference frequency generation;    integrated optics devices;    intersubband transitions;    quantum cascade laser;    terahertz;   

DOI  :  10.1515/nanoph-2018-0093

学科分类：社会科学、人文和艺术（综合）

来源: De Gruyter

【 摘 要 】

Terahertz quantum cascade laser (QCL) sources based on intra-cavity difference frequency generation are currently the only electrically pumped monolithic semiconductor light sources operating at room temperature in the 1–6-THz spectral range. Relying on the active regions with the giant second-order nonlinear susceptibility and the Cherenkov phase-matching scheme, these devices demonstrated drastic improvements in performance in the past several years and can now produce narrow-linewidth single-mode terahertz emission that is tunable from 1 to 6 THz with power output sufficient for imaging and spectroscopic applications. This paper reviews the progress of this technology. Recent efforts in wave function engineering using a new active region design based on a dual-upper-state concept led to a significant enhancement of the optical nonlinearity of the active region for efficient terahertz generation. The transfer of Cherenkov devices from their native semi-insulating InP substrates to high-resistivity silicon substrates resulted in a dramatic improvement in the outcoupling efficiency of terahertz radiation. Cherenkov terahertz QCL sources based on the dual-upper-state design have also been shown to exhibit ultra-broadband comb-like terahertz emission spectra with more than one octave of terahertz frequency span. The broadband terahertz QCL sources operating in continuous-wave mode produces the narrow inter-mode beat-note linewidth of 287 Hz, which indicates frequency comb operation of mid-infrared pumps and thus supports potential terahertz comb operation. Finally, we report the high-quality terahertz imaging obtained by a THz imaging system using terahertz QCL sources based on intra-cavity difference frequency generation.

【 授权许可】

CC BY