Unique optical characteristics of a Fabry-Perot resonator with embedded PT-symmetrical grating

TL;DR

This paper investigates a novel Fabry-Perot resonator with an embedded PT-symmetrical grating, revealing unique unidirectional optical properties, exotic absorption and amplification behaviors, and stable single-mode lasing due to PT symmetry.

Contribution

It introduces a new resonator design with PT-symmetrical gratings that exhibit unidirectional reflection and stable single-mode lasing, advancing optical resonator technology.

Findings

Unidirectional transparency and reflection depending on illumination side

Exotic absorption and amplification behaviors observed

Stable single-mode lasing without mode hopping

Abstract

We explore the optical properties of a Fabry-Perot resonator with an embedded Parity-Time (PT) symmetrical grating. This PT-symmetrical grating is non diffractive (transparent) when illuminated from one side and diffracting (Bragg reflection) when illuminated from the other side, thus providing a unidirectional reflective functionality. The incorporated PT-symmetrical grating forms a resonator with two embedded cavities. We analyze the transmission and reflection properties of these new structures through a transfer matrix approach. Depending on the resonator geometry these cavities can interact with different degrees of coherency: fully constructive interaction, partially constructive interaction, partially destructive interaction, and finally their interaction can be completely destructive. A number of very unusual (exotic) nonsymmetrical absorption and amplification behaviors are observed. The proposed structure also exhibits unusual lasing performance. Due to the PT-symmetrical grating, there is no chance of mode hopping; it can lase with only a single longitudinal mode for any distance between the distributed reflectors.