GaN-based vertical-cavity surface-emitting laser incorporating a TiO2 high-index-contrast grating

We demonstrate the first electrically injected GaN-based VCSEL with a TiO₂ high-contrast grating (HCG) as the top mirror. The TiO₂-HCG rested directly on the n-GaN without an airgap for mechanical stability. A VCSEL with an aperture diameter of 10 μm had a threshold current of 25 mA under pulsed operation at room temperature. Multiple longitudinal modes coexist around 400 nm, each TM-polarized with a linewidth of 0.5 nm (spectral resolution limited). This first demonstration of a TiO₂-HCG VCSEL offers a new route to achieve polarization pinning and could also allow additional benefits such as post-growth setting of resonance wavelength.