Micromachined Vertical Cavity Surface Emitting Lasers—Athermalization, Tuning, and Multiwavelength Integration

We review the wavelength engineering of micromachined vertical cavity surface emitting lasers (VCSELs), including the wavelength athermalization, wavelength tuning, and multiple wavelength integration. The integration of a thermally actuated cantilever enables us to tailor the temperature dependence of lasing wavelengths. The thermal drift of lasing wavelengths in conventional single-mode semiconductor lasers, which is typically 0.07 nm/K, can be compensated by using the thermal actuation of a cantilever mirror. We are able to realize “athermal operation” of VCSELs under uncooled operations. This novel function could be useful for WDM optical interconnects, local area networks, and access networks with narrow channel spacing under uncooled operations. In addition, continuous wavelength tuning can be realized by using either electrothermal or electrostatic force actuation of the cantilever structure, which provides the athermal and tunable operation at the same time. Also, the lithography defined multiwavelength integration of an athermal VCSEL array is addressed.