Deeply Etched Semiconductor/Benzocyclobutene Distributed Bragg Reflector Laser Combined with Multiple Cavities for 1.5-µm-Wavelength Single-Mode Operation

Abstract

Single-mode GaInAsP lasers at a wavelength of 1.5 µm, fabricated using deep dry-etching technology are presented. In the novel design, the high reflectivity of a fifteen-element distributed Bragg reflector (DBR) is combined with the spectral selectivity of multiple cavities (MC) to achieve single-mode operation with high output efficiency. The etched structure was buried with polymer benzocyclobutene (BCB) in order to reduce the diffraction loss between coupled cavities, to passivate the sidewalls of the waveguide and to protect the structure from damage due to process handling. MC lasers with different numbers of cavities were analyzed by the transfer matrix method (TMM) including groove losses and the results of analysis are compared with experimental results of fabricated devices. For a coupled cavity (CC) laser, which has only two cavities, a threshold current of 11 mA and a submode suppression ratio (SMSR) of 36 dB at a bias current of 1.8 times the threshold were obtained for 5-µm-wide mesa stripe geometry.