Instantaneous Spectral Span Of 2.85 - 8.40 Μm Achieved In A Cr:Zns Laser Pumped Subharmonic Opo

Keywords

Frequency comb; Mid-infrared; Nonlinear optics; Octave wide spectrum; Optics parametric oscillator; Parametric process; Spectroscopy

Abstract

Degenerate (subharmonic) optical parametric oscillators (OPO) show great promise for the generation of broadband mid-infrared (MIR) frequency combs. Their main features are low pump threshold, dramatic extension of the spectrum of the pump laser, and phase locking to the pump frequency comb. Here we report on obtaining instantaneous spectrum ranging from 2.85 to 8.40 μm at -40 dB level from a subharmonic OPO pumped by an ultrafast Cr2+:ZnS laser. Our experimental setup includes a free running Kerr lens mode locked 2.35 μm Cr2+:ZnS laser, with 62-fs time-bandwidth limited pulse duration, 630-mW average power, and 79 MHz repetition rate that synchronously pumps a ring-cavity orientation-patterned (OP-GaAs) based OPO. A 0.5-mm-long OP-GaAs crystal has a quasi-phase-matching (QPM) period of 88 μm and is designed to provide a broadband parametric gain at OPO degeneracy. A 0.3-mm-thick ZnSe wedge inside the cavity was used to minimize group velocity dispersion. Spectral span of 1.56 octaves in the MIR that we achieved can be further improved by fabricating an in-coupling dielectric mirror with (i) broader reflectivity range and (ii) with compensation of the residual group velocity dispersion. The broad spectrum achieved, 2.85 - 8.40 μm (2320 cm-1 wide instantaneous span), overlaps with a plethora of fundamental molecular IR resonances and can be used for frequency comb spectroscopic detection applied to such fields as remote sensing, study of fast combustion dynamics and medical diagnostics, to name a few.

Publication Date

1-1-2017

Publication Title

Proceedings of SPIE - The International Society for Optical Engineering

Volume

10088

Document Type

Article; Proceedings Paper

Personal Identifier

scopus

DOI Link

https://doi.org/10.1117/12.2256046

Socpus ID

85020262383 (Scopus)

Source API URL

https://api.elsevier.com/content/abstract/scopus_id/85020262383

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