The mode characteristics of photonic crystal vertical cavity surface emitting laser

Abstract

In this paper, we report the single mode operation of PC-VCSEL. The PC- VCSEL is similar to standard VCSEL except that it has photonic crystal defined by holes in the top distributed Bragg reflector. The two-dimensional photonic crystal (2-D PhC) structure is applied to lateral mode control of VCSEL. The optical confinement in VCSEL is realized by adding air-holes in the top (DBR). The holes are arranged periodically such that they form a triangular or square symmetric pattern. Light emitting aperture is formed by removing some air holes centered at photonic crystal pattern. By adjusting the photonic crystal parameters and air-holes depth, a variety of optical mode characteristic can be achieved. The characteristics of lasing lateral modes in PhC-VCSEL were analyzed by etching depth related effective index method. The contribution of PhC parameters such as lattice constant a, holes diameter d and uniform material index n to lateral mode characteristic is investigated systematically. Then two dimensional PhC was fabricated using electron beam lithography (EBL) and inductive coupled plasma reactive ion etching (ICP-RIE) on the surface of the VCSEL's top DBR. A single-fundamental- mode output power bigger than 1mW, threshold current below 5 mA, Full Width Half Maximum (FWHM) of lasing spectrum is less than 0.06 nm and over 30dB SMSR PhC-VCSEL was obtained. The lateral mode characteristics affected by different current injection was also considered.