A self-starting miniaturized short-pulse terahertz laser has been reported by the Italian nanoscience Research Institute

The production of stable ultra-short (femtosecond to picosecond) terahertz frequency radiation pulse sequences with high instantaneous intensity is a basic requirement for light-matter interactions in the field of metrography and ultra-high speed communication. In solid-state electro-pumped lasers, the main way to generate short pulses is through passive mode-locking. However, this goal has not been achieved within the terahertz range, which is one of the longest sustained goals in the past two decades. In fact, the implementation of passive mode-locking has long been considered limited by the inherent hindrance of the rapid recovery time associated with the gain between subbands in terahertz lasers.

Recently, Elisa Riccardi, Valentino Pistore, NEST, CNR -- Istituto Nanoscienze and Scuola Normale Superiore, Miriam S. Vitiello et al., in Nature Photonics, reported a self-starting miniaturized short-pulse terahertz laser using an original device architecture consisting of an entire cavity of a 2.30-3.55thz line laser in a bimetallic semiconductor. Layered surface patterning of graphene saturable absorbers. Self-starting pulse emission with 4.0 picosecond long pulses is demonstrated in a compact, all-electronic, all-passive and inexpensive configuration.

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

Figure 1: Device schematic and optical simulation.

Figure 2: Multi-layer graphene saturable absorber distribution distributed graphene saturable absorber, DGSA-Quantum

cascade lasers Quantum cascade lasers, electrical and optical properties of QCL.

Figure 3: time-domain spectroscopy, TDS emission curve.

Figure 4. Maxwell-bloch dynamic simulation.