Two-crystal mid-infrared optical parametric oscillator for absorption and dispersion dual-comb spectroscopy

Abstract

We present a femtosecond optical parametric oscillator (OPO) containing two magnesium-doped periodically poled lithium niobate crystals in a singly resonant ring cavity, pumped by two mode-locked Yb-fiber lasers. As such, the OPO generates two idler combs (up to 220 mW), covering a wavelength range from 2.7 to 4.2 μm, from which a midinfrared dual-comb Fourier transform spectrometer is constructed. By detecting the heterodyning signal between the two idler beams a full broadband spectrum of a molecular gas can be observed over 250 cm −1 within 70 μs with a spectral resolution of 15 GHz. The absorption and dispersion spectra of acetylene and methane have been measured around 3000 cm −1 , indicating that this OPO represents an ideal broadband mid-infrared source for fast chemical sensing.

Laser spectroscopy for breath analysis: towards clinical implementation

“…Different broadband spectroscopic methods such as Virtually Imaged Phase Array (VIPA) spectroscopy [84], Vernier spectroscopy [85], and dual-comb spectroscopy [86,87] are also utilized in the MIR range yielding faster measurement times and/or higher detection sensitivity paving the way towards achieving the specifications needed for biomedical applications. In addition, the recent dual-comb spectroscopic results using a DFG [88] or an OPO [89] based on an Orientation Patterned Gallium Phosphide (OPGaP) crystal-a newly developed nonlinear material-extend the available detection wavelength range to 12 µm.…”

Femtosecond optical parametric oscillators toward real-time dual-comb spectroscopy

“…These apertures cause significant diffraction losses for the higher-order modes. This is beneficial for heterodyned detection since the two output idler beams should have an optimal spatial overlap, which can be achieved when both beams are in the TEM 00 mode [36]. From the fast infrared detector, the heterodyned signal is low-pass filtered (up to 50 MHz) and sampled at 250 MHz.…”

“…To solve the issues mentioned in the previous section, a two-crystal OPO within a ring cavity is introduced; more details of this OPO can be found in [36]. Within the OPO, two 5-mm-long PPLN crystals are used for optical frequency conversion to generate two idlers that are spatially separated.…”

“…Specifically, for trace gas sensing applications, the wavelength region between 2 and 20 μm is of great interest, as gases, liquids, and solids have unique absorption and dispersion features in this region, associated with their molecular rotational-vibrational transitions. For mid-infrared dual-comb spectroscopy, the light sources are mainly based on different frequency generation (DFG) and optical parametric oscillation [34][35][36]. The advantage of DFG sources is that the offset frequency of the comb is passively locked to zero and that only the stabilization of the repetition frequency needs to be considered for mid-infrared frequency comb generation.…”

A Tunable Mid-Infrared Solid-State Laser with a Compact Thermal Control System

“…Since mid-infrared lasers have minimum attenuation in atmospheric transmission and cover the absorption peaks of many atoms and molecules, they are widely used in laser spectroscopy, atmosphere monitoring, photoelectric detection, remote sensing survey and many other fields [1][2][3][4]. The pump laser is one of the most important key modules in tunable mid-infrared solid-state lasers.…”