Coherent octave-spanning mid-infrared supercontinuum generated in As_2S_3-silica double-nanospike waveguide pumped by femtosecond Cr:ZnS laser

Abstract

A more than 1.5 octave-spanning mid-infrared supercontinuum (1.2 to 3.6 μm) is generated by pumping a As 2 S 3 -silica "double-nanospike" waveguide via a femtosecond Cr:ZnS laser at 2.35 μm. The combination of the optimized group velocity dispersion and extremely high nonlinearity provided by the As 2 S 3 -silica hybrid waveguide enables a ~100 pJ level pump pulse energy threshold for octave-spanning spectral broadening at a repetition rate of 90 MHz. Numerical simulations show that the generated supercontinuum is highly coherent over the entire spanning wavelength range. The results are important for realization of a high repetition rate octave-spanning frequency comb in the mid-infrared spectral region. References and links1. A. Schliesser, N. Picqué, and T. W. Hänsch, "Mid-infrared frequency combs," Nat. Photonics 6(7), 440-449 (2012). 2. U. Keller, "Recent developments in compact ultrafast lasers," Nature 424(6950), 831-838 (2003). 3. P. Maddaloni, P. Malara, G. Gagliardi, and P. D. Natale, "Mid-infrared fibre-based optical comb," New J. Phys. Fermann, L. Wondraczek, and P. St. J. Russell, "Mid-Infrared supercontinuum generation in As 2 S 3 -silica "nanospike" step-index waveguide," Opt.

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“…Due to the presence of many molecular "finger-print" absorption features in this spectral region, a simultaneous coverage of this range will enable the parallel detection and identification of a vast number of chemicals [1,2]. This wavelength range can be covered by numerous different schemes, each with their own strengths and weaknesses in terms of complexity, simultaneous bandwidth, power, efficiency, and pulse durations [3][4][5][6][7][8]. Yet, the most popular method of coherent broadband MIR generation remains nonlinear downconversion from the nearinfrared-a spectral region where many high-power driving lasers are available [4,7,[9][10][11][12][13][14][15][16][17][18].…”

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