Short mode-locked pulses from planarized Y-coupled THz lasers

TL;DR

This paper demonstrates a novel on-chip THz quantum cascade laser that uses active mode-locking with microwave modulation to generate coherent short pulses of 2.3 ps duration, offering a direct and efficient THz source.

Contribution

It introduces a new active mode-locking technique for planarized Y-coupled THz quantum cascade lasers, enabling direct generation of short, coherent THz pulses on-chip.

Findings

Generated 2.3 ps pulses with active mode-locking.

Achieved emission bandwidths of 500-700 GHz.

Operated at a central frequency of 2.9 THz.

Abstract

Short THz pulses are highly attractive both for fundamental research and practical applications in this underdeveloped region of the electromagnetic spectrum. Typically, THz pulses are generated using nonlinear optical methods, starting from a high-power visible or near-IR mode-locked source, but usually suffer from low conversion efficiencies. Here, we present a direct on-chip THz source of coherent short pulse trains based on active mode-locking of an inverse-designed planarized Y-coupled THz quantum cascade laser. By employing quasi-resonant microwave modulation of the asymmetric laser cavity, mode-locked pulses as short as 2.3 ps are generated, with emission bandwidths spanning 500 and 700 GHz at a central frequency of 2.9 THz.