Grating-Assisted Microcylinder Surface-Emitting Laser

A novel design of grating-assisted microcylinder surface-emitting laser (GAMSEL) is presented. GAMSEL has two gratings: top grating and side grating. Both gratings have the number of periods close to the azimuthal mode number of the whispering gallery mode (WGM) supported by the microcylinder cavity, therefore, they behave like second-order gratings of a straight waveguide. The top grating scatters the WGM vertically so as to form the surface emission while the side grating selects the mode having the proper emission pattern to lase. Through the cooperation of the two gratings, GAMSEL becomes a single-mode surface-emitting laser. Due to its small volume, GAMSEL is predicted through simulation to have a threshold current about 1 mA and a direct modulation bandwidth higher than 40 GHz. Besides, relying on the lateral microcylinder cavity, GAMSEL does not require highly reflective mirrors as vertical-cavity surface-emitting lasers do, which makes this design easily apply to different wavelengths such as the near infrared 1310- and 1550-nm wavelength bands.