Adaptive Dual-Comb Spectroscopy With 1200-h Continuous Operation Stability

Abstract

Dual-comb spectroscopy (DCS), without moving mirrors, enables fast optical sampling of molecular vibrations and results in high-resolution and high-accuracy Fouriertransform spectra. This motionless technique holds much promise in gas sensing and environmental monitoring. However, in many cases, these applications require a mature device continuously operating for days or even months, thus posing a challenge to long-term stability of this delicate technique. In this paper, we demonstrate the feasibility of DCS for long-term routine spectral monitoring. A compact dual-comb spectrometer is built based on adaptive sampling and simple frequency stabilization schemes. The spectrometer is ceaselessly recording and displaying, in real time, transmission spectra of a phase-shifted fiber Bragg grating and of gas-phase samples for over 1200 h (50 days). We spectroscopically validate the system by measuring absorption lines of ν 1 + ν 3 band of C 2 H 2 and of 2ν 3 band of CH 4 and comparing the experimental data with HITRAN database.

High-speed hyperspectral four-wave-mixing microscopy with frequency combs

“…Furthermore, this low SNR and the short decay times of the excitons relative to the pulse repetition period made it unnecessary to process all of the data between bursts. We point out that these limitations are not fundamental to the technique and could be mitigated with several real-time correction schemes [16,21,18]. The SNR could also be improved by preventing the pumps beams from reaching the FWM-LO detector.…”

“…Due to the large size of the files that had to be saved after digitization for each pixel, each hyperspectral image took about 30 minutes of laboratory time to record even though only about 45 seconds worth of data was collected. This excessive acquisition time could be reduced using real-time techniques [16,17,18] that allow for significantly smaller file sizes. Further acquisition speed gains could come via faster raster scan control enabled for example by resonant galvanometer mirrors.…”

Terahertz Time-of-Flight Ranging with Adaptive Clock Asynchronous Optical Sampling

“…The beat notes detected by PD can be expressed as: f PD1 = f CW1 − (m f rA + f cepA ) f PD2 = f CW2 − (n f rA + f cepA ) f PD3 = f CW2 − (n′ f rB + f cepB ) f PD4 = f CW1 − (m′ f rB + f cepB ) where f r is the repetition rate and f cep is the carrier–envelope phase of Laser A and B. In order to avoid confusion due to mixing frequencies, the difference between the serial numbers of the beating teeth of the two combs is equal (m − n = m′ − n′) [ 31 , 32 ]. Afterwards, the effect of CW1 can be eliminated by mixing f PD1 and f PD4 as follows: f S2 = f PD4 − f PD1 = m f rA − m′ f rB + Δ f cep while the effect of CW2 can be eliminated by mixing f PD2 and f PD3 as follows: f S1 = f PD3 − f PD2 = n f rA − n′ f rB + Δ f cep …”

Standoff Chemical Detection Using Laser Absorption Spectroscopy: A Review

“…However, current DCS systems are complex and expensive because of the requirement for two fully stabilized OFCs with slightly different comb spacing. Note that DCS is an emerging new technology and also an extremely active area of research, consequently, many new developments are emerging to improve DCS performance, simplify its composition, and reduce its size [173,175,[188][189][190][191][192][193][194]. As a result, we fully believe that DCS will become more and more mature and may surpass traditional broadband spectroscopy for a wide range of applications.…”