Polarization mode control of two-dimensional photonic crystal laser by unit cell structure design

We demonstrate polarization mode selection in a two-dimensional (2D) photon ic crystal laser by controlling the geometry of the unit cell structure. As the band diagram of the square-lattice photonic crystal is influenced by t he unit cell structure, calculations reveal that changing the structure fro m a circular to an elliptical geometry should result in a strong modificati on of the electromagnetic field distributions at the band edges. Such a str uctural 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 wa velength and controlled polarization is in good agreement with the predicte d behavior.