SIMULTANEOUS-OPTIMIZATION OF MEMBRANE REFLECTANCE AND TUNING VOLTAGE FOR TUNABLE VERTICAL-CAVITY LASERS

Micromachined wavelength tunable vertical cavity lasers are attractive for applications ranging from wavelength division multiplexing to spe ctroscopy. An improved tunable structure that incorporates a partial a nti-reflection coating to increase coupling between the air gap and th e semiconductor cavity, and a more flexible micromachine process that enables independent optimization of the central reflector region and d eformable membrane structure are described. This combination of struct ural and process modifications enables decoupling the tradeoffs betwee n wavelength tuning rate and threshold current, as well as the tradeof fs between top mirror reflectance and tuning voltage. With these impro ved approaches, a 2.5 pair dielectric distributed Bragg reflector hybr id membrane top mirror produced singlemode devices with a 23 nm wavele ngth tuning range and multi-transverse-mode devices with a 30 nm wavel ength tuning range. Threshold current, differential quantum efficiency , and lasing mode are characterized as a function of membrane bias. (C ) 1998 American Institute of Physics.