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Proceedings Paper

Octave-wide frequency comb centered at 4 µm based on a subharmonic OPO with Hz-level relative linewidth
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Paper Abstract

We study coherence properties of a more-than-octave-wide (2.6-7.5 μm) mid-IR frequency comb based on a 2-μm Tmfiber- laser-pumped degenerate (subharmonic) optical parametric oscillator (OPO) that uses orientation-patterned gallium arsenide (OP-GaAs) as gain element. By varying intracavity dispersion, we observed a 'phase' transition from a singlecomb state (at exactly OPO degeneracy) to a two-comb state (near-degenerate operation), characterized by two spectrally overlapping combs (signal and idler) with distinct carrier-envelope offset frequencies. We achieve this by generating a supercontinuum (SC) from the mode-locked Tm laser that spans most of the near-IR range, and observing RF beats between the SC and parasitic sum-frequency light (pump + OPO) that also falls into the near-IR. We found RF linewidth to be <15 Hz (a resolution of our spectrum analyzer), which proves that coherence of the pump laser comb is preserved to a high degree in a subharmonic OPO. Transition to a two-comb state was characterized by a symmetric splitting of the RF peak. Low pump threshold (down to 7 mW), high (73 mW) average power and high (up to 90%) pump depletion make this comb source very attractive for numerous applications including trace molecular detection and chemical sensing with massively parallel spectral data acquisition.

Paper Details

Date Published: 4 March 2016
PDF: 6 pages
Proc. SPIE 9731, Nonlinear Frequency Generation and Conversion: Materials, Devices, and Applications XV, 973103 (4 March 2016); doi: 10.1117/12.2218035
Show Author Affiliations
V. O. Smolski, CREOL, The College of Optics and Photonics, Univ. of Central Florida (United States)
IPG Photonics Mid-IR Lasers (United States)
J. Xu, CREOL, The College of Optics and Photonics, Univ. of Central Florida (United States)
P. G. Schunemann, BAE Systems (United States)
K. L. Vodopyanov, CREOL, The College of Optics and Photonics, Univ. of Central Florida (United States)


Published in SPIE Proceedings Vol. 9731:
Nonlinear Frequency Generation and Conversion: Materials, Devices, and Applications XV
Konstantin L. Vodopyanov; Kenneth L. Schepler, Editor(s)

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