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Nonlinear Silicon waveguides produce tunable frequency combs spanning 2.0-8.5 ?m



Nima Nader, Abijith S. Kowligy, Jeffrey T. Chiles, Eric J. Stanton, Henry R. Timmers, Alexander J. Lind, Kimberly Briggman, Scott Diddams, Flavio Caldas da Cruz, Richard Mirin, Sae Woo Nam, Daniel M. Lesko


We present fully air clad suspended-silicon waveguides for efficient nonlinear interactions limited only by the silicon transparency. Novel fork-shaped couplers provide efficient input (< 2 dB) and broadband 3 dB output coupling spanning 6.0-8.5 υm. Suspended-Si waveguides produce tunable infrared frequency combs spanning 2.1 octaves in the mid-infrared when pumped at 3.1 υm with 140 pJ pulses. The optical bandwidth spans 2.0-8.5 υm with spectra that can be tailored by geometrical dispersion engineering. Interpulse temporal coherence of the combs is demonstrated via optical multi-heterodyne in a dual-comb setup. Individual comb-modes are resolved with 30 dB extinction ratio and 100 MHz spacing in the wavelength range of 4.8- 8.5 υm. These sources are used for broadband, high signal-to-noise gas- and liquid-phase dual-comb spectroscopy with the achieved figure of merit of 1.1x10^6 Hz^0.5 at 100 MHz comb- mode resolution. These results are relevant for compact sensors with applications in chip-based chemical analysis and spectroscopy.


mid-infrared photonics, supercontinuum generation, frequency combs


Nader, N. , Kowligy, A. , Chiles, J. , Stanton, E. , Timmers, H. , Lind, A. , Briggman, K. , Diddams, S. , Caldas, F. , Mirin, R. , Nam, S. and Lesko, D. (2019), Nonlinear Silicon waveguides produce tunable frequency combs spanning 2.0-8.5 ?m, Optica (Accessed April 21, 2024)
Created September 24, 2019, Updated February 23, 2021