LAUSR

A distributed Bragg reflector (DBR) composed of Y₂O₃-doped HfO₂ (YDH)/SiO₂ layers with high reflectivity spectrum centered at a wavelength of ∼240 nm is fabricated using radio-frequency magnetron sputtering. Before the DBR deposition, optical properties for a single layer of YDH, SiO₂, and HfO₂ thin films were studied using spectroscopic ellipsometry and spectrophotometry. To investigate the performance of YDH as a material for the high refractive index layer in the DBR, a comparison of its optical properties was made with HfO₂ thin films. Due to larger optical bandgap, the YDH thin films demonstrated higher transparency, lower extinction coefficient, and lower absorption coefficient in the UV-C regime (especially for wavelengths below 250 nm) compared to the HfO₂ thin films. The fabricated YDH/SiO₂ DBR consisting of 15 periods achieved a reflectivity higher than 99.9% at the wavelength of ∼240 nm with a stopband of ∼50 nm. The high reflectivity and broad stopband of YDH/SiO₂ DBRs will enable further advancement of various photonic devices such as vertical-cavity surface-emitting lasers, resonant-cavity light-emitting diodes, and resonant-cavity photodetectors operating in the UV-C wavelength regime.