Broadband ultraviolet-visible frequency combs from cascaded high-harmonic generation in quasi-phase-matched waveguides
Scott Diddams, Jay Rutledge, Anthony Catanese, Daniel Hickstein, Thomas K. Allison, Abijith Kowligy
High-harmonic generation (HHG) provides short-wavelength light that is useful for precision spectroscopy and probing ultrafast dynamics. Here, we report ecient, phase-coherent harmonic generation up to 9th-order (333 nm) in chirped periodically poled lithium niobate waveguides driven by phase-stable 12-nJ, 100 fs pulses at 3 \mum, with 100 MHz repetition rate. A mid-infrared to ultraviolet-visible conversion efficiency as high as 10% is observed, amongst an overall 23% conversion of the fundamental to all harmonics. We verify the coherence of the harmonic frequency combs despite the complex highly nonlinear process. Numerical simulations based on a single broadband envelope equation with second-order nonlinearity give estimates for the conversion efficiency within approximately 1 order of magnitude over a wide range of experimental parameters. From this comparison we identify a dimensionless parameter, capturing the competition between group-velocity walkoff of the harmonics and three-wave mixing, that governs the cascaded HHG physics. These results can inform cascaded HHG in a range of different platforms.
, Rutledge, J.
, Catanese, A.
, Hickstein, D.
, Allison, T.
and Kowligy, A.
Broadband ultraviolet-visible frequency combs from cascaded high-harmonic generation in quasi-phase-matched waveguides, The Journal of Optical Society of America B, [online], https://doi.org/10.1364/JOSAB.427086, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=931935
(Accessed December 1, 2021)