Sub-terahertz and terahertz generation in long-wavelength quantum cascade lasers

Kazuue Fujita,Shohei Hayashi,Akio Ito,Masahiro Hitaka,Tatsuo Dougakiuchi

doi:10.1515/nanoph-2019-0238

Abstract

Abstract Terahertz quantum cascade laser sources with intra-cavity non-linear frequency mixing are the first room-temperature electrically pumped monolithic semiconductor sources that operate in the 1.2–5.9 THz spectral range. However, high performance in low-frequency range is difficult because converted terahertz waves suffer from significantly high absorption in waveguides. Here, we report a sub-terahertz electrically pumped monolithic semiconductor laser. This sub-terahertz source is based on a high-performance, long-wavelength (λ ≈ 13.7 μm) quantum cascade laser in which high-efficiency terahertz generation occurs. The device produces peak output power of 11 μW within the 615–788 GHz frequency range at room temperature. Additionally, a source emitting at 1.5 THz provides peak output power of 287 μW at 110 K. The generated terahertz radiation of <2 THz is mostly attributable to the optical rectification process in long-wavelength infrared quantum cascade lasers.

Highlights

Terahertz quantum cascade laser sources with intra-cavity non-linear frequency mixing are the first room-temperature electrically pumped monolithic semiconductor sources that operate in the 1.2–5.9 THz spectral range
THz quantum cascade lasers (QCLs) sources based on intra-cavity differencefrequency generation (DFG) [12], which were developed as alternative THz-QCL sources, are the only electrically driven monolithic semiconductor light sources that are capable of room-temperature operation in the THz spectral range [13,14,15]
Using the high design flexibility of QCL structures with giant second-order non-linear susceptibility [16], these devices have expanded spectral coverage that extends over nearly the entire 1–6 THz range [13,14,15]. Because this approach does not require population inversion to be maintained across the THz transitions in a QCL, THz-QCLs based on DFG may be suitable for lower- frequency THz generation

Summary

Introduction

Abstract: Terahertz quantum cascade laser sources with intra-cavity non-linear frequency mixing are the first room-temperature electrically pumped monolithic semiconductor sources that operate in the 1.2–5.9 THz spectral range. This non-linear QCL device demonstrates a THz peak output power of 11 μW at room temperature (293 K) with multimode sub-THz emission at a frequency of approximately 700 GHz. For high-power THz generation in a non-linear QCL source, high MIR pump powers are required.

Results

Conclusion