RF Injection of THz QCL Combs at 80 K Emitting over 700 GHz Spectral Bandwidth

Andres Forrer,Mattias Beck,Giacomo Scalari,Jérôme Faist,Lorenzo Bosco

doi:10.3390/photonics7010009

Abstract

We report about RF injection locking of an homogeneous THz quantum cascade laser operating at 3 THz central frequency. The extremely diagonal nature of the optical transition, combined with low-loss copper-based double-metal waveguides, allow CW operation up to 105 K and CW power in excess of 5.6 mW measured at 80 K. Terahertz emission spanning up to 600 GHz, together with a narrow beatnote, indicate comb operation at 80 K, and strong RF injection clearly modifies the laser spectrum up to 700 GHz spectral bandwidth making these devices ideal candidates for an on-chip dual comb spectrometer.

Highlights

Frequency combs have had a tremendous impact in several domains since their demonstration in the early 2000s [1,2]
High-precision spectroscopy [3] and especially dual comb spectroscopy [4] have greatly benefited from the advancement of such sources
The understanding that sources with perfectly equidistant modes and a well-defined phase relation can be achieved even without ultrafast pulses opened the door to the extension of frequency combs to the mid-IR and THz through optically pumped microresonators [5] and electrically pumped quantum cascade lasers [6,7]

Summary

Introduction

Frequency combs have had a tremendous impact in several domains since their demonstration in the early 2000s [1,2]. In order to improve the performance of our laser ridges, in the present study (for comb generation), we employ low-loss Cu–Cu metal waveguides following the procedure described in Ref.

Results

Conclusion