Broadband 1-GHz mid-infrared frequency comb

Abstract

Mid-infrared (MIR) spectrometers are invaluable tools for molecular fingerprinting and hyper-spectral imaging. Among the available spectroscopic approaches, GHz MIR dual-comb absorption spectrometers have the potential to simultaneously combine the high-speed, high spectral resolution, and broad optical bandwidth needed to accurately study complex, transient events in chemistry, combustion, and microscopy. However, such a spectrometer has not yet been demonstrated due to the lack of GHz MIR frequency combs with broad and full spectral coverage. Here, we introduce the first broadband MIR frequency comb laser platform at 1 GHz repetition rate that achieves spectral coverage from 3 to 13 µm. This frequency comb is based on a commercially available 1.56 µm mode-locked laser, robust all-fiber Er amplifiers and intra-pulse difference frequency generation (IP-DFG) of few-cycle pulses in χ(2) nonlinear crystals. When used in a dual comb spectroscopy (DCS) configuration, this source will simultaneously enable measurements with μs time resolution, 1 GHz (0.03 cm−1) spectral point spacing and a full bandwidth of >5 THz (>166 cm−1) anywhere within the MIR atmospheric windows. This represents a unique spectroscopic resource for characterizing fast and non-repetitive events that are currently inaccessible with other sources.

Compact mid-infrared dual-comb spectrometer over 3–4 μm via intra-pulse difference frequency generation in LiNbO3 waveguides

“…The coupling efficiency is 60%. In general, some spatial optical components, including wedge and chirp mirrors, were required to control the pulse chirp before IPDFG [ 26 , 28 ] . These extra spatially manipulated modules increased total loss and system complexity.…”

“…In this two-branch structure, delay control is required to stabilize the pump-signal pulse walkoff in the time domain and suppress the intensity noise of MIR pulses [25] . Recently, several studies have reported the simple method of MIR comb generation via intra-pulse DFG (IPDFG) [26][27][28][29][30] . Through precise chirp management of the supercontinuum, a single branch can provide natural spatiotemporal alignment for the pump and signal pulses, achieving multi-octave-spanning MIR combs [26][27][28] .…”

On-chip highly efficient octave-spanning long-wavelength mid-infrared optical parametric generation with a 74% quantum efficiency

“…The measurement and simulation results qualitatively agree well with each other. 17,[38][39][40][41][42] , OPG [35][36][37] , DFG [21][22][23][24][25][26][27] and IPDFG 4,[28][29][30][31][32][33][34] in the long-wavelength MIR region (>5 μm) based on bulk nonlinear crystals, and the demonstrated on-chip integrated OPG based on ZGP χ (2) waveguide. A quantum efficiency of 74% at a pump pulse energy of 6.5 nJ is demonstrated, which is enhanced by more than 2 folds compared to the state-of-art parametric conversions.…”

GHz Figure‐9 Er‐Doped Optical Frequency Comb Based on Nested Fiber Ring Resonators

“…[ 20 ] For dual‐comb spectroscopy, OFCs with 1 GHz repetition rate strike a delicate balance between measurement speed and spectral resolution. [ 21 ] In spaceborne LIDAR systems, OFCs serve as a high‐accuracy reference over a broad spectral band for multiple types of greenhouse gas detection. Pulsed LIDAR systems often use nanosecond modulation, requiring combs with spacing larger than GHz to ensure that each LIDAR pulse can overlap with one of the OFC pulses in the time domain.…”