Polarization Mode Control of Two-Dimensional Photonic Crystal Laser by Unit Cell Structure Design

TLDR

The band diagram of a square‑lattice photonic crystal depends on unit cell shape, and switching from circular to elliptical units is predicted to strongly alter electromagnetic field distributions at band edges. The study demonstrates that adjusting the unit cell geometry in a 2D photonic crystal laser can select the polarization mode of the emitted light. The authors fabricated a square‑lattice photonic crystal with elliptical unit cells and integrated it with gain media to achieve polarization‑mode control. Coherent 2D lasing at a single wavelength with controlled polarization was observed, matching the predicted behavior.

Abstract

We demonstrate polarization mode selection in a two-dimensional (2D) photonic crystal laser by controlling the geometry of the unit cell structure. As the band diagram of the square-lattice photonic crystal is influenced by the unit cell structure, calculations reveal that changing the structure from a circular to an elliptical geometry should result in a strong modification of the electromagnetic field distributions at the band edges. Such a structural modification is expected to provide a mechanism for controlling the polarization modes of the emitted light. A square-lattice photonic crystal with the elliptical unit cell structure has been fabricated and integrated with a gain media. The observed coherent 2D lasing action with a single wavelength and controlled polarization is in good agreement with the predicted behavior.