Continuously Tunable, Polarization Stable SWG MEMS VCSELs at 1.55 $\mu{\rm m}$

We present polarization stable, tunable long-wavelength vertical-cavity-surface-emitting lasers (VCSELs) at 1.55 μm based on InP. The tuning is accomplished by a two-chip membrane mounting technique denoted as bulk-micro-machining. The membrane consists of a GaAs-based distributed Bragg reflector and represents the top mirror. By its electro thermal actuation, cavity tuning occurs. This results in a continuous wavelength shift. Polarization stability is achieved by an implemented semiconductor/air subwavelength grating (SWG) written in the top-most layers of the membrane facing the VCSEL eye after mounting process. The SWG integration is realized by a combination of holographic lithography, barrel, and reactive ion etching. The manufactured micro-electro-mechanical-system SWG-VCSELs show a continuous, polarization stable wavelength tuning of ~ 25 nm with a peak optical power of 4 mW fiber-coupled in an MMF and thresholds of 3-3.5 mA.