Strong Laser Emission Modulation by Coherent Perfect Absorption Inside Complex‐Coupled Distributed Feedback Laser Diodes

Abstract

The proof‐of‐concept of the exploitation of Coherent Perfect Absorption (CPA) in electrically‐injected distributed‐feedback laser sources is reported. Capitalizing on the essence of CPA as “light extinction by light”, an integrated laser‐modulator scheme emerges. The key ingredient compared to conventional single‐frequency laser diodes is a careful periodic in‐phase modulation of both real and imaginary parts of the complex grating index profile that enables both single‐frequency operation and 40 dB line purity at the Bragg frequency. It is shown that this combination is most apt for the operation of CPA as a modulation mechanism that respects the laser spectral purity. The specific proof‐of‐concept is based on an ultra‐short external cavity formed by a metallic micro‐mirror, whose role is to generate the second beam of more conventional CPA interferometric approaches. The implemented complex‐coupled grating is compatible with existing industrial technologies and promising for real‐life laser source applications. Furthermore, the concept can be directly transferred to other material platforms and other wavelengths ranging from terahertz to ultraviolet.