Abstract
Abstract Octave-spanning frequency comb generation in the deep mid-infrared (>5.5 μm) typically requires a high pump power, which is challenging because of the limited power of narrow linewidth lasers at long wavelengths. We propose twofold dispersion engineering for a Ge-on-Si microcavity to enable both dispersion flattening and dispersion hybridization over a wide band from 3.5 to 10 μm. A two-octave mode-locked Kerr frequency comb can be generated from 2.3 to 10.2 μm, with a pump power as low as 180 mW. It has been shown that dispersion flattening greatly enhances the spectral broadening of the generated comb, whereas dispersion hybridization improves its spectral flatness.
Highlights
Frequency comb generation in the mid-infrared has become an intensely investigated topic for spectroscopy and imaging applications [1]
We propose twofold dispersion engineering for a Ge-on-Si microcavity to enable both dispersion flattening and dispersion hybridization over a wide band from 3.5 to 10 μm
Many of the optical materials used far for mid-IR photonics become strongly absorptive above 5.5 μm wavelength, whereas the term “mid-IR” means a large spectral range, from 2.5 to 20 μm, i.e. three octaves [10,11,12,13], with many molecular fingerprints to be detected
Summary
Frequency comb generation in the mid-infrared (mid-IR) has become an intensely investigated topic for spectroscopy and imaging applications [1]. A twooctave mode-locked Kerr frequency comb can be generated from 2.3 to 10.2 μm, with a pump power as low as 180 mW. If the higher-order (>2) dispersions and other nonlinear effects such as self-steepening and Raman scattering are ignored, cavity-soliton-based mode-locked combs have their bandwidth related to the following physical parameters [16]:
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