Ultrashort pulse generation from a graphene-coupled passively mode-locked terahertz laser

TL;DR

This paper reports the first demonstration of passive mode-locking in a solid-state THz laser using graphene-based saturable absorbers, producing ultra-short pulses in a compact, all-electronic setup.

Contribution

It introduces a novel device architecture with graphene saturable absorbers enabling passive mode-locking in THz lasers, overcoming previous recovery time limitations.

Findings

Achieved self-starting 4.0-ps pulses in the THz range.

Demonstrated passive mode-locking in a solid-state THz laser.

Developed a compact, all-electronic THz laser system.

Abstract

The generation of stable trains of ultra-short (fs-ps), terahertz (THz)-frequency radiation pulses, with large instantaneous intensities, is an underpinning requirement for the investigation of light-matter interactions, for metrology and for ultra-high-speed communications. In solid-state electrically-pumped lasers, the primary route for generating short pulses is through passive mode-locking. However, this has not yet been achieved in the THz range, defining one of the longest standing goals over the last two decades. In fact, the realization of passive mode-locking has long been assumed to be inherently hindered by the fast recovery times associated with the intersubband gain of THz lasers. Here, we demonstrate a self-starting miniaturized ultra-short pulse THz laser, exploiting an original device architecture that includes the surface patterning of multilayer-graphene saturable absorbers distributed along the entire cavity of a double-metal semiconductor 2.30-3.55 THz wire laser. Self-starting pulsed emission with 4.0-ps-long pulses in a compact, all-electronic, all-passive and inexpensive configuration is demonstrated.