DUV coherent light emission from ultracompact microcavity wavelength conversion device

Abstract

A unique design of our ultracompact microcavity wavelength conversion device exploits the simple principle that the wavelength conversion efficiency is proportional to the square of the electric field amplitude of enhanced pump light in the microcavity, and expands the range of suitable device materials to include crystals that do not exhibit birefringence or ferroelectricity. Here, as a first step toward practical applications of all-solid-state ultracompact deep-ultraviolet coherent light sources, we adopted a low-birefringence paraelectric SrB4O7 crystal with great potential for wavelength conversion and high transparency down to 130 nm as our device material, and demonstrated 234 nm deep-ultraviolet coherent light generation, whose wavelength band is expected to be used for on-demand disinfection tools that can irradiate the human body.

Polarity Inversion of GaN via AlN Oxidation Interlayer Using Metal–Organic Vapor Phase Epitaxy

“…These polarizations result in strong optical nonlinearity, [ 10 ] making nitride semiconductors also suitable for application in wavelength conversion devices. The large absorption edge energies of GaN (3.4 eV) and AlN (6.2 eV) make them suitable for application in spontaneous parametric downconversion devices for use as quantum light sources in the bandwidth range around 800 nm, which is detectable with Si photodiodes [ 11 ] and deep‐ultraviolet (DUV) second‐harmonic generation (SHG) devices, for sterilization and disinfection, [ 12 ] respectively.…”

Second harmonic generation from a-plane GaN vertical monolithic microcavity pumped with femtosecond laser

“…[1][2][3][4][5] Deep ultraviolet (DUV) light near 230 nm in wavelength has gathered much attention as on-demand disinfection tools that can irradiate human bodies, [6][7][8] and DUV SHG devices are one of the candidates. [9][10][11][12][13] SPDC devices are popular choices for light sources for quantum optical circuits 14,15) Nitride semiconductors such as GaN and AlN are suitable for wavelength conversion devices because they have large optical nonlinearity comparable to ferroelectric materials, wide transparent wavelength range, and high optical damage tolerance which exceeds them. [16][17][18][19][20][21] AlN can be applied to the DUV SHG devices pumped by blue/ green lights.…”

“…We have proposed a microcavity phase matching method that does not rely on ferroelectricity or birefringence. 13,24) This approach significantly expands freedom of the device structure and material selection, as it can be applied to any nonlinear optical crystal with high optical damage tolerance. By confining the pump light in the microcavity, the light intensity can be significantly enhanced.…”

“…We have successfully demonstrated SHG from microcavity structures that utilize two different low-birefringence paraelectric materials: GaN and SrB 4 O 7 (SBO). 13,24) These materials possess large optical nonlinearity and high optical damage tolerance. Specifically, SBO has high transparency down to 130 nm.…”

Second harmonic generation in GaN transverse quasi-phase-matched waveguide pumped with femtosecond laser

“…[1][2][3][4] Far-UV lights near 230 nm in wavelength are effective for sterilization and harmless to humans, and second harmonic generation (SHG) devices made of AlN, whose can be used for the application. 5,6) GaN spontaneous parametric down-conversion (SPDC) devices pumped by a 400 nm band InGaN laser can be applied as quantum light sources. A conventional longitudinal quasi-phase-matched (QPM) structure with periodic polarity inversion domains along the wave propagation direction is used for achieving high-efficiency wavelength conversion.…”