Cavity-enhanced optical frequency comb spectroscopy in the mid-infrared application to trace detection of hydrogen peroxide

Abstract

Cavity-enhanced optical frequency comb spectroscopy in the mid-infrared application to trace detection of hydrogen peroxide. Abstract We demonstrate the first cavity-enhanced optical frequency comb spectroscopy in the mid-infrared wavelength region and report the sensitive real-time trace detection of hydrogen peroxide in the presence of a large amount of water. The experimental apparatus is based on a midinfrared optical parametric oscillator synchronously pumped by a high-power Yb:fiber laser, a high-finesse broadband cavity, and a fast-scanning Fourier transform spectrometer with autobalancing detection. The comb spectrum with a bandwidth of 200 nm centered around 3.76 µm is simultaneously coupled to the cavity and both degrees of freedom of the comb, i.e. the repetition rate and carrier envelope offset frequency, are locked to the cavity to ensure stable transmission. The autobalancing detection scheme reduces the intensity noise by a factor of 300, and a sensitivity of 5.4 × 10 −9 cm −1 Hz −1/2 with a resolution of 800 MHz is achieved (corresponding to 6.9 × 10 −11 cm −1 Hz −1/2 per spectral element for 6000 resolved elements). This yields a noise equivalent detection limit for hydrogen peroxide of 8 parts-per-billion (ppb); in the presence of 2.8 % of water the detection limit is 130 ppb. Spectra of acetylene, methane, and nitrous oxide at atmospheric pressure are also presented, A. Foltynowicz ( ) · Applied physics. B, Lasers and optics (Print),

Mid-infrared continuous-filtering Vernier spectroscopy using a doubly resonant optical parametric oscillator

“…The coherence of comb sources enables measurements over long distances [5] and efficient coupling to multipass cells [3] and cavities [6] to enhance the interaction length with the sample. The high absorption sensitivity in combination with the strong intensities of the fundamental transitions translates into low concentration detection limits for many molecular species.…”

“…Both approaches enable measurements with frequency resolution and precision provided by the comb with no influence of the instrumental line shape and are suitable for broadband precision spectroscopy [4,14]. Mechanical MIR FTS has been successfully combined with enhancement cavities [6,15] and enabled, e.g., acquisition of rotationally resolved spectra of cold complex molecules [16]. The use of the cavities with mechanical FTS requires a high-bandwidth lock and the transmitted spectral range is limited by the cavity dispersion [6].…”

“…Mechanical MIR FTS has been successfully combined with enhancement cavities [6,15] and enabled, e.g., acquisition of rotationally resolved spectra of cold complex molecules [16]. The use of the cavities with mechanical FTS requires a high-bandwidth lock and the transmitted spectral range is limited by the cavity dispersion [6]. Moreover, the measurement time is of the order of a second, fundamentally limited by the movement of the mirror, and the mechanical interferometer is a rather bulky detection system.…”

Continuous Vernier filtering of an optical frequency comb for broadband cavity-enhanced molecular spectroscopy

“…They are defined by the repetition rate of the femtosecond oscillator f rep and by a carrier-envelop offset frequency f ceo translating the whole comb of a constant value comprised between 0 and f rep , each comb mode frequency being indexed by an integer n and defined as ν las n = n.f rep + f ceo . Several approaches [1,2,3,4,5,6,9] have been designed to combine OFC's with the extended path lengths associated with high finesse cavities, to attain high sensitivity in molecular absorption spectra. Some resolve the comb mode structure (with 1 GHz mode locked laser) [1,2], some are fast (around or below the ms timescale of acquisition) [3,4], some particularly sensitive (baseline noise around 10 −4 ) [5], but none truly exploit the full bandwidth of OFC, restricting the accessible spectral range to roughly a few hundred of wavenumbers, around ten percent of the entire range of a typical Titanium:Sapphir (Ti:Sa) modelocked laser.…”

Fourier transform and Vernier spectroscopy using an optical frequency comb at 3–54 μm

“…In particular, OPOs based on orientation-patterned gallium arsenide (OP-GaAs) crystals pumped by Cr:ZnSe or Tm:fiber femtosecond lasers have made it possible to reach wavelengths beyond ~4.8 µm, a barrier for the well-established oxidebased materials [7,8]. Both DFG and OPO sources have been used for MIR optical frequency comb spectroscopy with different detection methods, namely a Fourier transform spectrometer [9][10][11][12][13], a virtually imaged phased array (VIPA) [14,15], mode-resolved Vernier spectroscopy [16], and dual comb spectroscopy [17,18]. However, the spectral range of all previous demonstrations was limited to <4.8 µm.…”