Narrow Linewidth Laser Based on Extended Topological Interface States in One-Dimensional Photonic Crystals

TL;DR

This paper demonstrates a topological interface state-extended one-dimensional photonic crystal laser that achieves ultra-narrow linewidth, stable single-mode operation, and precise wavelength control, promising advancements in high-power, narrow-linewidth laser technology.

Contribution

It introduces a novel 1D topological interface state-extended photonic crystal laser with enhanced robustness, linewidth narrowing, and precise wavelength control, combining theoretical and experimental validation.

Findings

Achieved approximately 150 kHz linewidth in 1550 nm laser.

Demonstrated stable single-mode operation from 60 to 420 mA.

Enabled precise wavelength spacing control of 0.796 nm ± 0.003 nm.

Abstract

Recent advances in topological one-dimensional photonic crystal concepts have enabled the development of robust light-emitting devices by incorporating a topological interface state (TIS) at the cavity center. In this study, we theoretically and experimentally demonstrate a one-dimensional TIS-extended photonic crystal (1D-TISE-PC) structure. By integrating a linearly dispersive zero-index one-dimensional photonic crystal structure with a four-phase shift sampled grating, photons propagate along the cavity without phase differences, enhancing the robustness to material variations and extending the TIS. Our findings indicate that extending the TIS promotes a more uniform photon distribution along the laser cavity and mitigates the spatial hole burning (SHB) effect. We fabricated and characterized a 1550 nm sidewall 1D-TISE-PC semiconductor laser, achieving stable single-mode operation across a wide current range from 60 to 420 mA, with a side-mode suppression ratio of 50 dB. The 1D-TISE-PC structure exhibited a linewidth narrowing effect to approximately 150 kHz Lorentzian linewidth. Utilizing reconstruction equivalent-chirp technology for the 4PS sampled grating enabled precise wavelength control in 1D-TISE-PC laser arrays, achieving a wavelength spacing of 0.796 nm +- 0.003 nm. We show that the TIS still exists in the TISE cavity and topological protection is preserved. Its mode extension characteristics mitigate the SHB so narrows the linewidth. We argue that the design simplicity and improvement of the fabrication tolerance make this architecture suitable for high-power and narrow-linewidth semiconductor lasers development.