Properties of micromechanically tunable VCSELs

Abstract

Tunable vertical cavity surface emitting lasers (VCSELs) are very attractive candidates for employment in various areas of interest, like optical communications or gas sensing. During the last decade these types of components have been demonstrated. In this paper we present a micromechanically realization of an optically pumped 1.55 μm tunable VCSEL and its characteristics. The investigated device comprises two chips. The first chip, a half-cavity VCSEL chip, contains the bottom Bragg-mirror and the active layers. The second chip is a micromechanically manufactured Bragg-mirror membrane chip. After aligning, both chips form together the VCSEL cavity. Wavelength tuning is achieved by thermal actuation of the membrane mirror due to current flow and the subsequent deflection of the mirror membrane resulting in a change of the resonance wavelength. Such a micromachined two-chip VCSEL device is investigated and discussed. In particular, properties like the side mode suppression ratio, relative intensity noise and polarization during actuation and their dependence on the properties of the micromachined mirror-membrane are analyzed. Remarkable results are e.g. the side mode suppression ratio dependence on the pump spot size, the dependence of the relative intensity noise of the VCSEL on the pump laser noise, and stable polarization due to the membrane design.