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Mid-infrared frequency comb generation via cascaded quadratic nonlinearities in quasi-phase-matched waveguides



Abijith S. Kowligy, Alexander J. Lind, Daniel D. Hickstein, David R. Carlson, Henry R. Timmers, Nima Nader, Flavio Caldas da Cruz, Gabriel G. Ycas


We demonstrate mid-infrared (MIR) frequency comb generation in periodically poled lithium niobate (PPLN) waveguides pumped by nanojoule pulses from a 1.5 um mode-locked Er:fiber laser. The cascaded-c(2) nonlinearity in PPLN yields a nearly octave-spanning supercontinuum in the near infrared (NIR) and phase-matched intra-pulse difference-frequency generation (DFG) results in mid-infrared (MIR) frequency comb generation. We experimentally demonstrate (i) narrow-band mid-IR generation, tunable from 4—5 um with a single chip and (ii) broadband mid-IR combs in aperiodically poled waveguides. We further show that theoretical models can reliably predict the broadband, multi-octave experimental spectra, and can be used to inform waveguide designs to tailor mid-infrared spectra. Our results identify a path to a simple single-branch approach to mid-infrared frequency comb generation in an integrated platform using commercial Er:fiber technology. Abstract:
Optics Letters


Frequency comb, integrated photonics, mid-infrared, spectroscopy
Created April 5, 2018, Updated February 21, 2019