Half-Watt average power femtosecond source spanning 3–8 µm based on subharmonic generation in GaAs

Frequency combs with a wide instantaneous spectral span covering the 3–20 µm molecular fingerprint region are highly desirable for broadband and high-resolution frequency comb spectroscopy, trace molecular detection, and remote sensing. We demonstrate a novel approach for generating high-average-power middle-infrared (MIR) output suitable for producing frequency combs with an instantaneous spectral coverage close to 1.5 octaves. Our method is based on utilizing a highly-efficient and compact Kerr-lens mode-locked Cr2+:ZnS laser operating at 2.35-µm central wavelength with 6-W average power, 77-fs pulse duration, and high 0.9-GHz repetition rate; to pump a degenerate (subharmonic) optical parametric oscillator (OPO) based on a quasi-phase-matched GaAs crystal. Such subharmonic OPO is a nearly ideal frequency converter capable of extending the benefits of frequency combs based on well-established mode-locked pump lasers to the MIR region through rigorous, phase- and frequency-locked down conversion. We report a 0.5-W output in the form of an ultra-broadband spectrum spanning 3–8 µm measured at 50-dB level.

[1]  Valentin Gapontsev,et al.  Three optical cycle mid-IR Kerr-lens mode-locked polycrystalline Cr(2+):ZnS laser. , 2015, Optics letters.

[2]  P. Schunemann,et al.  Coherence properties of a 2.6-7.5  μm frequency comb produced as a subharmonic of a Tm-fiber laser. , 2016, Optics letters.

[3]  Valentin Gapontsev,et al.  Kerr-lens mode-locked femtosecond polycrystalline Cr2+:ZnS and Cr2+:ZnSe lasers. , 2014, Optics express.

[4]  Konstantin L. Vodopyanov,et al.  Broadband degenerate OPO for mid-infrared frequency comb generation. , 2011, Optics express.

[5]  Kevin F. Wall,et al.  High peak power ultrafast Cr:ZnSe oscillator and power amplifier , 2016, SPIE LASE.

[6]  Kirk A. Ingold,et al.  Cascaded half-harmonic generation of femtosecond frequency combs in the mid-infrared , 2016 .

[7]  Jun Ye,et al.  Phase-stabilized, 1.5 W frequency comb at 2.8-4.8 microm. , 2009, Optics letters.

[8]  Kevin F. Lee,et al.  Midinfrared frequency comb from self-stable degenerate GaAs optical parametric oscillator. , 2015, Optics express.

[9]  Albert Schliesser,et al.  Mid-infrared frequency combs , 2012, Nature Photonics.

[10]  Michel Piché,et al.  23-kW peak power femtosecond pulses from a mode-locked fiber ring laser at 2.8 μm , 2016, LASE.

[11]  S B Mirov,et al.  Cr:ZnS laser-pumped subharmonic GaAs optical parametric oscillator with the spectrum spanning 3.6-5.6  μm. , 2015, Optics letters.

[12]  Evgeni Sorokin,et al.  Femtosecond Cr2+-Based Lasers , 2015, IEEE Journal of Selected Topics in Quantum Electronics.

[13]  Valentin Gapontsev,et al.  140 W Cr:ZnSe laser system. , 2016, Optics express.

[14]  Valentin Gapontsev,et al.  Frontiers of Mid-IR Lasers Based on Transition Metal Doped Chalcogenides , 2018, IEEE Journal of Selected Topics in Quantum Electronics.

[15]  Peter G. Schunemann,et al.  Advances in nonlinear optical crystals for mid-infrared coherent sources , 2016 .

[16]  Kai Zhong,et al.  Instantaneous spectral span of 2.85 - 8.40 μm achieved in a Cr:ZnS laser pumped subharmonic OPO , 2017, LASE.

[17]  Ferenc Krausz,et al.  High-power sub-two-cycle mid-infrared pulses at 100 MHz repetition rate , 2015, Nature Photonics.

[18]  Luke Maidment,et al.  Molecular fingerprint-region spectroscopy from 5 to 12  μm using an orientation-patterned gallium phosphide optical parametric oscillator. , 2016, Optics letters.

[19]  Qitian Ru,et al.  Self-referenced octave-wide subharmonic GaP optical parametric oscillator centered at 3  μm and pumped by an Er-fiber laser. , 2017, Optics letters.

[20]  Mike Mirov,et al.  Progress in Mid-IR Lasers Based on Cr and Fe-Doped II–VI Chalcogenides , 2015, IEEE Journal of Selected Topics in Quantum Electronics.

[21]  Fabrizio R Giorgetta,et al.  Mid-infrared optical frequency combs based on difference frequency generation for molecular spectroscopy. , 2015, Optics express.

[22]  Valentin Gapontsev,et al.  Multi-Watt mid-IR femtosecond polycrystalline Cr(2+):ZnS and Cr(2+):ZnSe laser amplifiers with the spectrum spanning 2.0-2.6 µm. , 2016, Optics express.

[23]  Vladimir Pervak,et al.  Coherence properties of a broadband femtosecond mid-IR optical parametric oscillator operating at degeneracy. , 2012, Optics express.

[24]  I. Hartl,et al.  Optically Referenced Tm-Fiber-Laser Frequency Comb , 2012 .

[25]  Valentin Gapontsev,et al.  Ultrafast middle-IR lasers and amplifiers based on polycrystalline Cr:ZnS and Cr:ZnSe , 2017 .

[26]  Martin M. Fejer,et al.  Multiphoton absorption and nonlinear refraction of GaAs in the mid-infrared , 2007 .

[27]  F. Stutzki,et al.  Thulium-doped fiber chirped-pulse amplification system with 2 GW of peak power. , 2016, Optics letters.