Optical parametric oscillation with distributed feedback in cold atoms

TL;DR

This paper demonstrates a novel mirrorless laser system using cold atoms in a one-dimensional lattice, combining Bragg reflection and four-wave mixing to achieve tunable, conical optical parametric oscillation.

Contribution

It introduces a new cold atom-based distributed feedback laser that integrates Bragg reflection and parametric gain for mirrorless lasing.

Findings

Achieved mirrorless optical parametric oscillation with cold atoms.

Controlled the cone angle of emission via lattice periodicity.

Demonstrated tunability of the laser output.

Abstract

There is currently a strong interest in mirrorless lasing systems, in which the electromagnetic feedback is provided either by disorder (multiple scattering in the gain medium) or by order (multiple Bragg reflection). These mechanisms correspond, respectively, to random lasers and photonic crystal lasers. The crossover regime between order and disorder, or correlated disorder, has also been investigated with some success. Here, we report one-dimensional photonic-crystal lasing (that is, distributed feedback lasing) with a cold atom cloud that simultaneously provides both gain and feedback. The atoms are trapped in a one-dimensional lattice, producing a density modulation that creates a strong Bragg reflection with a small angle of incidence. Pumping the atoms with auxiliary beams induces four-wave mixing, which provides parametric gain. The combination of both ingredients generates a mirrorless parametric oscillation with a conical output emission, the apex angle of which is tunable with the lattice periodicity.