Phase-stabilized 100 mW frequency comb near 10 μm

Abstract

Long-wavelength mid-infrared (MIR) frequency combs with high power and flexible tunability are highly desired for molecular spectroscopy, including investigation of large molecules such as C60. We present a high power, phase-stabilized frequency comb near 10 μm, generated by a synchronously pumped, singly resonant optical parametric oscillator (OPO) based on AgGaSe2. The OPO can be continuously tuned from 8.4 to 9.5 μm, with a maximum average idler power of 100 mW at the center wavelength of 8.5 μm. Both the repetition rate (frep) and the carrier-envelope offset frequency (fceo) of the idler wave are phase-locked to microwave signals referenced to a Cs clock. We describe the detailed design and construction of the frequency comb, and discuss potential applications for precise and sensitive direct frequency comb spectroscopy.

Dual-comb spectroscopy for high-temperature reaction kinetics

“…The use of two frequency combs, dual-comb spectroscopy, has been applied to high-temperature, nonreacting conditions in a rapid compression machine by Draper et al at 704 µs time-resolution and also by Schroeder et al in the exhaust of a gas turbine at high temperatures and 10-60 s time-resolution [4,8]. Draper Efforts to extend DCS into the 3-20 µm region have involved distributed feedback generation DFG [14], optical parametric oscillators (OPO) [15][16][17], and quantum-cascadelaser (QCL) approaches [6,7,[18][19][20]. Obtaining coherency between two frequency combs is an enabling factor for DCS and DFG approaches can achieve this readily.…”

Mode-locked short pulses from an 8 μm wavelength semiconductor laser

“…Due to the lack of suitable gain media, methods for the generation of pulses in the molecular fingerprint region beyond 5 μm wavelength have so far relied on non-linear downconversion of near-infrared pulses 7 . Established techniques such as optical parametric oscillators 8 or difference frequency generation 9 , 10 either require sophisticated optical setups with tabletop dimensions or are restricted to mW-level of output power.…”

Infrared Comb Spectroscopy of Buffer-Gas-Cooled Molecules: Toward Absolute Frequency Metrology of Cold Acetylene

“…OPO frequency combs have been reported using MgO-PPLN (1.5 W at 2.8–4.8 m, 30 mW at 2.2–3.7 m) [ 41 , 42 ], OP-GaAs (70 mW at 2.6–7.5 m, 10 mW at 5.2–6.2 m) [ 43 , 44 ], AgGaSe (17.5 mW at 4.8–6.0 m) [ 45 ], and OP-GaP (30 mW at 2.3–4.8 m) [ 46 ]. At longer wavelengths, based on a AgGaSe crystal, an OPO pumped by a Tm-fiber comb led to the realization of a phase-stabilized OFC continuously tunable from 8.4 to 9.5 m with a maximum average idler power of 100 mW at 8.5 m [ 47 ]. Effective MIR combs with an instantaneous output spectrum of 3–12.5 m have also been obtained with subharmonic OPOs based on OP-GaAs as a gain nonlinear crystal, pumped by a Kerr-lens mode-locked 2.35- m laser [ 48 ].…”