Far-field pattern control and light-extraction enhancement of deep-ultraviolet light-emitting diodes with large-area Fresnel zone plate nano-structures

Abstract

Conventional methods using high-purity quartz lenses to control deep-ultraviolet light-emitting diode (DUV-LED) far-field patterns have limitations, including small effective apertures and high cost. We apply phase-type Fresnel zone plates to control the beam angle and enhance light extraction efficiency (LEE) for DUV-LEDs on sapphire and AlN substrates. We demonstrate highly-collimated optics-free DUV-LED emissions with full width at half maximum far-field divergence angles of 40° and 10° on sapphire and AlN substrates at a peak emission wavelength of 279 nm and 273 nm, respectively. LEE enhancements of 1.4 and 1.5 times for DUV-LEDs on sapphire and AlN substrates, respectively, are also achieved.