Design of AlN-subwavelength grating for deep ultraviolet wavelength reflector operating at 244 nm of wavelength

Highly reflective reflector (> 99.9%) operating at deep ultraviolet (DUV) wavelength region around 244 nm was proposed by using subwavelength grating (SWG) patterned AlN substrate. Structural parameters of AlN-SWG were desgined for DUV reflector using the wavenumber dispersion relation of the eiegenmdoes resulting from its periodic refractive index distribution. The electromagnetic field calculated by finite-difference time-domain (FDTD) method revealed the polarization selective reflection characteristics of the designed AlN-SWG, and the SWG can achieve more than 99% reflectivity of p-polarization (the electric field is perpendicular to the grating fingers) at the DUV wavelength of 244 nm. This extremely high reflectivity, polarization selectivity and compactness of our AlN-SWG are very useful for various DUV applications, such as cavity of DUV laser diodes.