Simultaneous optimization of membrane reflectance and tuning voltage for tunable vertical cavity lasers

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Abstract
Micromachined wavelength tunable vertical cavity lasers are attractive for applications ranging from wavelength division multiplexing to spectroscopy. An improved tunable structure that incorporates a partial anti-reflection coating to increase coupling between the air gap and the semiconductor cavity, and a more flexible micromachine process that enables independent optimization of the central reflector region and deformable membrane structure are described. This combination of structural and process modifications enables decoupling the tradeoffs between wavelength tuning rate and threshold current, as well as the tradeoffs between top mirror reflectance and tuning voltage. With these improved approaches, a 2.5 pair dielectric distributed Bragg reflector hybrid membrane top mirror produced singlemode devices with a 23 nm wavelength tuning range and multi-transverse-mode devices with a 30 nm wavelength tuning range. Threshold current, differential quantum efficiency, and lasing mode are characterized as a function of membrane bias.