High efficient linearly polarized light emission from InGaN/GaN LED with patterned nanostructures

We proposed and demonstrated an integrated high energy efficient and high linearly polarized InGaN/GaN green LED grown on (0001) oriented sapphire with combined nanostructure converter and polarizer system. Different from those conventional polarized light emission generated with plasmonic metallic grating in which at least 50% high energy loss happens inherently due to high reflection of TE component of the electric field, a reflecting metasurface with 2D elliptic metal cylinder array (EMCA) that functions as a half-wave plate was integrated at the bottom of a LED such that the back-reflected TE component that is otherwise lost by a dielectric/metal bi-layered wire grids (DMBiWG) polarizer on the top emitting surface of the LED can be converted to desired TM polarized emission after reflecting from the metasurface, which significantly enhances the polarized light emission efficiency. Experimental results show that the extraction efficiency of the polarized emission can be increased by 40% on average in a wide angle of ±60° compared to that with naked bottom of sapphire substrate or 20% compared to that with reflecting Al film on the bottom of sapphire substrate while an extinction ratio (ER) of higher than 20 dB within an angle of ±60° can be simultaneously obtained directly from an InGaN/GaN LED. Our results show the possibility of simultaneously achieving high degree of polarization and high polarization extraction efficiency at integrated device level and advance the field of GaN LED toward energy efficiency, multi-functional applications in illumination, display, medicine, and light manipulation.