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Continuous ultraviolet to blue-green astrocomb.

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Cheng, Yuk Shan 
Mitchell, Toby 
Piskunov, Nikolai 


Cosmological and exoplanetary science using transformative telescopes like the ELT will demand precise calibration of astrophysical spectrographs in the blue-green, where stellar absorption lines are most abundant. Astrocombs-lasers providing a broadband sequence of regularly-spaced optical frequencies on a multi-GHz grid-promise an atomically-traceable calibration scale, but their realization in the blue-green is challenging for current infrared-laser-based technology. Here, we introduce a concept achieving a broad, continuous spectrum by combining second-harmonic generation and sum-frequency-mixing in an MgO:PPLN waveguide to generate 390-520 nm light from a 1 GHz Ti:sapphire frequency comb. Using a Fabry-Pérot filter, we extract a 30 GHz sub-comb spanning 392-472 nm, visualizing its thousands of modes on a high-resolution spectrograph. Experimental data and simulations demonstrate how the approach can bridge the spectral gap present in second-harmonic-only conversion. Requiring only [Formula: see text]100 pJ pulses, our concept establishes a new route to broadband UV-visible generation at GHz repetition rates.


Acknowledgements: The authors gratefully acknowledge grant funding from the UK Science and Technologies Facilities Council (ST/Y001273/1, ST/S001328/1, ST/V000403/1, ST/X002306/1, ST/N002997/1, and ST/V000918/1); the Royal Academy of Engineering (RCSRF1718639 and RCSRF2223-1678); and the Knut and Alice Wallenberg Scholarship 2021.


5108 Quantum Physics, 51 Physical Sciences

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Nat Commun

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Springer Science and Business Media LLC
RCUK | Science and Technology Facilities Council (STFC) (ST/S001328/1, ST/V000403/1, ST/N002997/1, ST/V000918/1, ST/Y001273/1, ST/X002306/1)
Royal Academy of Engineering (RCSRF1718639, RCSRF2223-1678)