A research team at Osaka University has successfully developed an ultra-compact microresonator device fundamentally different from conventional wavelength conversion devices. This breakthrough has allowed the device to generate vacuum ultraviolet (VUV) light with a wavelength of 199 nm through wavelength conversion.
With the rapid advancement of IoT (Internet of Things) and 5G (fifth-generation mobile communication systems) technologies, there is an increasing demand for VUV laser light with wavelengths below 200 nm. Such light can be precisely focused into ultra-small spots, making it ideal for applications like micromachining, lithography, and the inspection of wafers and photomasks.
However, existing VUV laser sources are typically large gas lasers with high operational costs, underscoring the need for next-generation light sources that are compact, efficient, and maintenance-free. While wavelength conversion technology holds promise for realizing all-solid-state VUV laser sources, traditional device structures combined with wavelength conversion crystals fall short of meeting the requirements for these advanced systems. As a result, developing wavelength conversion devices with innovative structures and crystals has become essential.
The SBO microresonator-based SHG device developed by the team offers a potential replacement for conventional large-scale VUV laser systems, enabling compact and highly efficient next-generation light sources. Additionally, similar configurations could be adapted to create devices that utilize other nonlinear optical effects beyond SHG.
For instance, by leveraging the extremely small wavelength conversion layer, broadband photon pair generation devices could be developed. These devices have the potential to facilitate high-resolution imaging of water-rich organs within the body-a challenging task for conventional optical coherence tomography (OCT)-which could advance the early detection and treatment of diseases.
Lead author Tomoaki Nambu says "Our efforts are now focused on realizing an integrated deep ultraviolet light source, with an emphasis on practical social implementation."
Fig. 1
Schematic of SBO microcavity SHG device.
Credit: Tomoaki Nambu
Fig. 2
SHG demonstration. (a) Spectra of 199 nm SH wave pumped by 398 nm fundamental wave (red: SH wave, blue: fundamental wave). (b) Dependence of SH wave intensity on fundamental wave power. (c) Dependence of SH wave intensity on central SH wavelength.
Credit: Tomoaki Nambu
Fig. 3
All-Solid-State VUV laser source: (a) Conventional complex system, (b) simplified system enabled by the SBO microcavity SHG device.
Credit: Tomoaki Nambu
The article, "199 nm vacuum-ultraviolet second harmonic generation from SrB4O7 vertical microcavity pumped with picosecond laser," was published in Applied Physics Express at DOI: https://doi.org/10.35848/1882-0786/ad69fe.
