Single-Mode Vertical Cavity Surface Emitting Laser via High-Order Transverse Mode Expansion

In this article, we propose a method of realizing single mode VCSEL by expanding its higher order transverse mode more out of its gain region, while maintaining its fundamental mode inside. This will result in less optical gain for the VCSEL's higher order mode than that for its fundamental mode, and then result in the single mode output of the VCSEL. A Top Cavity and a Bottom Cavity are introduced into VCSEL's top and bottom DBR respectively to achieve this purpose. The mode expansion phenomenon is verified by simulation, and the VCSEL is fabricated. Finally, a single-mode VCSEL with a side-mode suppression ratio greater than 40 dB, a threshold current of 0.5 mA, and a maximum output power of 0.27 mW is obtained.