Alignment-free difference frequency light source tunable from 5 to 20 µm by mixing two independently tunable OPOs

Abstract

Tunable mid-infrared ultrashort lasers have become an essential tool in vibrational spectroscopy in recent years. They enabled and pushed a variety of spectroscopic applications due to their high brilliance, beam quality, low noise, and accessible wavelength range up to 20 µm. Many state-of-the-art devices apply difference frequency generation (DFG) to reach the mid-infrared spectral region. Here, birefringent phase-matching is typically employed, resulting in a significant crystal rotation during wavelength tuning. This causes a beam offset, which needs to be compensated to maintain stable beam pointing. This is crucial for any application. In this work, we present a DFG concept, which avoids crystal rotation and eliminates beam pointing variations over a broad wavelength range. It is based on two independently tunable input beams, provided by synchronously pumped parametric seeding units. We compare our concept to the more common DFG approach of mixing the signal and idler beams from a single optical parametric amplifier (OPA) or oscillator (OPO). In comparison, our concept enhances the photon efficiency of wavelengths exceeding 11 µm more than a factor of 10 and we still achieve milliwatts of output power up to 20 µm. This concept enhances DFG setups for beam-pointing-sensitive spectroscopic applications and can enable research at the border between the mid-and far-IR range due to its highly efficient performance.

High–Efficiency, Widely Tunable MgO: PPLN Optical Parametric Oscillator

“…They compared this method to the traditional DFG approach of mixing the signal and idler beams from a single OPA or OPO (signal-idler DFG). In this work, they demonstrated that the output power and photon efficiency of the DFG wavelength under 10 µm generated by the signal-idler DFG are higher than that of dual OPO/OPA DFG [10]. Taking the much simpler configuration of the signal-idler DFG method into consideration, Photonics 2023, 10, 505 2 of 8 this approach is a very suitable option for generating tunable 4-7 µm femtosecond lasers with tens of milliwatts average power [11].…”

“…Due to the lack of mature laser gain media with emission in the mid-IR, parametric down-conversion of near-infrared (near-IR) sources through optical parametric oscillators (OPO), optical parametric amplifiers (OPA) or difference-frequency generation (DFG) remain the most efficient approaches to obtain high-power and widely tunable femtosecond mid-IR lasers [4][5][6][7]. Nowadays, there is a vast variety of research works on the generation of mid-IR lasers by parametric conversion, including intra-pulse difference frequency generation (IPDFG) [8], DFG using a dual-signal-wavelength OPO [9], and DFG between the signal and idler wavelengths of an OPA or OPO [10,11], as well as supercontinuum-seeded DFGs [12,13].…”

“…Photonics 2023, 10, x FOR PEER REVIEW 2 of 8 10 µm generated by the signal-idler DFG are higher than that of dual OPO/OPA DFG [10].…”

Metasurface‐Enhanced Infrared Spectroscopy: An Abundance of Materials and Functionalities

“…While the technological infrastructure for mid‐IR spectroscopy is not as mature as its counterpart in the visible/near‐IR spectral domains, increasingly powerful yet affordable mid‐IR sources are becoming available, including QCLs, [ 185 ] optical parametric oscillators (OPOs), [ 186 ] fiber‐based supercontinuum sources, [ 187 ] and frequency combs. [ 188 ] Along with the advances in mid‐IR sources/detectors as well as the growing palette of substrate materials, researchers have also improved the performance of on‐chip mid‐IR waveguide technologies toward the vision of realizing lab‐on‐a‐chip systems.…”