Mid-infrared 333 MHz frequency comb continuously tunable from 1.95 to 4.0 μm

• Published in: Optics letters Vol. 40; no. 17; p. 4178
• Main Authors: Balskus, Karolis, Zhang, Zhaowei, McCracken, Richard A, Reid, Derryck T
• Format: Journal Article
• Language: English
• Published: United States 01.09.2015
• ISSN: 1539-4794
• DOI: 10.1364/OL.40.004178

We report a 333 MHz femtosecond optical parametric oscillator in which carrier-envelope offset stabilization was implemented by using a versatile locking technique that allowed the idler comb to be tuned continuously over the mid-infrared range from 1.95 to 4.0 μm. A specially designed multi-section, multi-grating, periodically poled KTP crystal provided simultaneously phase-matched parametric down-conversion and pump + idler sum-frequency generation, enabling strong heterodyne signals with the pump supercontinuum (employed for locking) to be obtained across the tuning range of the device. The idler comb offset was stabilized to a 10 MHz reference frequency with a cumulative phase noise from 1 Hz-64 kHz of <1.3  rad maintained across the entire operating range, and average idler output powers up to 50 mW.