A step towards a daily use deep UV light source for sterilization and disinfection – sciencedaily
Researchers at the Graduate School of Engineering and the Center for Quantum Information and Quantum Biology at Osaka University have unveiled a new semiconductor second harmonic generation (SHG) device that converts infrared radiation into blue light. This work can lead to a convenient daily use deep ultraviolet light source for sterilization and disinfection.
Recently, deep ultraviolet light (DUV) sources have gained a lot of attention in sterilization and disinfection. In order to achieve a bactericidal effect while ensuring the safety of the user, a wavelength range of 220 to 230 nm is desirable. But DUV light sources in this wavelength range which are both durable and highly efficient have not yet been developed. Although wavelength conversion devices are promising candidates, conventional ferroelectric wavelength conversion materials cannot be applied to DUV devices due to the absorption edge.
Since nitride semiconductors such as gallium nitride and aluminum nitride have relatively high optical nonlinearity, they can be applied to wavelength conversion devices. Due to its transparency up to 210 nm, aluminum nitride is particularly suitable for DUV wavelength conversion devices. However, making structures with periodically reversed polarity like conventional ferroelectric wavelength converting devices has proven to be quite difficult.
The researchers proposed a novel monolithic microcavity wavelength conversion device without a reverse polarity structure. A fundamental wave is significantly enhanced in the microcavity with two distributed Bragg reflectors (DBRs), and counter-propagating second harmonic waves are efficiently emitted in phase on one side. As a first step towards a practical DUV light source, a gallium nitride microcavity device was fabricated through microfabrication technology, including dry etching and anisotropic wet etching for vertical and smooth DBR sidewalls. By obtaining a blue SH wave, the effectiveness of the proposed concept has been successfully demonstrated.
“Our apparatus can be adapted to use a wider range of materials. They can be applied to the emission of deep ultraviolet light or even to the generation of broadband photon pairs,” said lead author Masahiro Uemukai. The researchers hope that, because this approach does not rely on periodically inverted materials or structures, it will facilitate the construction of future nonlinear optical devices.
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