Highly Compact, High-Index Dielectric Nanostructures for Deep-Ultraviolet Devices

Efficient generation and management of deep ultraviolet (UV) light (wavelengths from 180 to 300 nm) is important for disinfection, remediation of toxic waste, spectroscopy, electronics manufacturing, and solid-state optoelectronic applications. While significant progress has been made in solid-state AlGaN-based UV light emitter materials, current device configurations utilize absorbing metal reflectors combined with traditional spreading material layers that reduce light-extraction and wall-plug efficiency. As such, new optical elements that reduce absorption losses, maximize UV reflection, and improve thermal management are necessary for accelerating the implementation of solid-state deep UV emitters.

Researchers at University of California, Santa Barbara have created wavelength-tunable, compact optical elements for efficient deep-UV reflection. These novel elements minimize absorption with a low extinction coefficient and >90% reflectance for the entire relevant UV wavelength range (180-365 nm) — all with improved wall-plug efficiency. Unlike reflective UV surfaces and protective dielectric coatings, this optical structure achieves upwards of 85% specular reflection near 200 nm and does not easily oxidize, making the devices commercially competitive compared to their counterpart’s high oxidation rates. Additionally, this invention enables back-end fabrication adaptability to a range of design wavelengths since the reflectors can be formed after epitaxial heterostructure growth and optical testing. This invention leverages intense, wavelength-tunable reflection, and narrow-band wavelength selectivity to become suitable for cleanup filters and narrow-band reflectors for commercially available lasers and LEDs. The compactness, efficiency, fabrication adaptability, and natively-nitride-based and freestanding nature of these elements positions them well to disrupt their current industry alternatives.