AlGaN membrane grating reflector

We report on AlGaN grating reflectors for short-wavelength applications, an alternative to conventional distributed Bragg reflectors that are difficult to make in a GaN-based system. An array of air-bridge AlGaN grating reflectors, with a period and filling factor of 430 nm and 0.55, was fabricated through holographic lithography and photoelectrochemical etching. Polarization-dependent microreflectance spectra were measured to confirm their consistency with simulation results. The reflectance measured at 532 nm for transverse-electric polarization was as high as ∼90%. We also found that the spectral range for high reflection correlates with the photonic Bloch band-edge modes.