Tunable, Continuous-Wave, Deep-Ultraviolet Laser Generation by Intracavity Frequency Doubling of Visible Fiber Lasers

Deep ultraviolet (DUV) lasers are essential elements to versatile applications such as spectroscopy and lithography, and several techniques including free-electron lasers, excimer lasers and high-order harmonic conversion have been developed for DUV laser generation, yet the wavelength tunability and compactness are still challenging. Here, for the first time, we experimentally demonstrate a compact tunable continuous-wave (CW) DUV laser source by direct intracavity frequency doubling of visible fiber lasers. Efficient green/yellowlaser emission is enabled by the down-conversion in the Ho3+- or Dy3+-doped ZBLAN fibers while the miniaturized cavity consists of a home-made fiber pigtail mirror and diffraction grating. The second harmonic generation from visible to ultraviolet is subsequently implemented by utilizing a BBO module intracavity. The achieved CWDUV lasers yield wavelength tuning range of 269.5-275.4 nm and 283.6-289.9 nm in the presence of an ultra-narrow linewidth of <0.025 nm. The produced power at 272.6 nm reaches 1.36 mW and a maximum visible-to-DUV efficiency of 5.3 parts per thousand is estimated with the green laser excitation. Our work therefore provides new possibilities for the realization of a new class of compact, wavelength tunable, and cost-effective CW DUV laser sources.

Automated summary

This study demonstrates for the first time a compact tunable continuous-wave (CW) deep ultraviolet (DUV) laser source. By directly intracavity frequency doubling visible fiber lasers, efficient DUV laser emission with a wide wavelength tuning range and narrow linewidth is achieved. The developed DUV laser source has high power and efficiency, providing new possibilities for DUV laser applications.