Yuusuke Takashima

Polarized emission characteristics of UV-LED with subwavelength grating

We investigated polarized emission from a GaN-based ultraviolet light-emitting diode (UV-LED) with a subwavelength grating (SWG) on the surface. The electroluminescence (EL) spectra showed that the UV-LED exhibits high polarization selectivity, as high as s-polarization: p-polarization = 4 : 1 at a wavelength of 360 nm. The polarized EL characteristics were discussed by the theoretical consideration of Bloch modes resulting from the spatial periodicity of the refractive index in the SWG region and also by finite difference time domain calculations to explore the electromagnetic field. We succeeded in demonstrating the feasibility of a highly polarized UV-LED grown on c-plane sapphire.

Influence of low-contrast subwavelength grating shape on polarization characteristics of GaN-based light-emitting diode emissions

Abstract. We analytically investigated the influence of grating shape on polarization characteristics of the emission from a GaN-based light-emitting diode with a low-contrast subwavelength grating (SWG), such as SiO2-SWG. The electromagnetic field distribution, calculated using the finite-difference time-domain method, predicted that the polarization characteristics strongly depend on the grating side slope. A trapezoid SiO2-SWG was fabricated on the GaN-based-LED using electron-beam lithography. The optical characteristics of the electroluminescence agreed with those theoretically predicted, and we succeeded in demonstrating the influence of grating shape on the polarization of LED emission.