Isotopic gas analysis through Purcell cavity enhanced Raman scattering

Abstract

Purcell enhanced Raman scattering (PERS) by means of a doubly resonant Fabry-Perot microcavity (mode volume ≈ 100 μm3 and finesse ≈ 30 000) has been investigated as a technique for isotopic ratio gas analysis. At the pump frequency, the resonant cavity supports a buildup of circulating power while simultaneously enabling Purcell spontaneous emission rate enhancement at the resonant Stokes frequency. The three most common isotopologues of CO2 gas were quantified, and a signal was obtained from 13C16O2 down to a partial pressure of 2 Torr. Due to its small size and low pump power needed (∼10 mW) PERS lends itself to miniaturization. Furthermore, since the cavity is resonant with the emission frequency, future improvements could allow it to serve as its own spectral analyzer and no separate spectroscopic device would be needed.

A Short Review of Cavity-Enhanced Raman Spectroscopy for Gas Analysis

“…In conclusion, CERS has the potential to be used in different applications. It can be further advanced by using microcavities, thereby utilizing quantum electrodynamical effects, such as the Purcell effect, to further enhance the Raman signal [ 113 , 114 ].…”

Self-sustained photothermal oscillations in high-finesse Fabry-Perot microcavities

“…They obviously constitute a substantial deviation from normal desired operation of a microcavity. In particular the fast local temperature variations introduced by this process, and possible secondary effects derived therefrom, such as the generation of thermoelastic waves [23,36], could affect quantum optical applications such as chemical sensing [9]. For example, the thermoelastic waves may generate a power-dependent background signal associated with Raman scattering in the coating [36].…”

A review of cavity-enhanced Raman spectroscopy as a gas sensing method

“…Petrak et al (120,121) analyzed the atmospheric gases and isotopes of CO 2 by CERS using a Fabry-Perot microcavity with PDH technique. The experimental setup and the details of the microcavity in these papers are shown in Figures 18 and 19, respectively.…”

“…Relative to free-space emissions, a gain factor of $10 7 is observed. With a 10-mW laser, the Raman scattering of CO 2 in ambient air (approximately 400 ppm) is detected (120), the three most common isotopologues of CO 2 gas are quantified (121), and a signal was obtained from 13 C 16 O 2 down to a partial pressure of 2 Torr (2666 ppm at 1 atm approximately). Because of the small cavity volume, the cavity length of a microcavity is too short, thus the laser-gas interaction length is Figure 19.…”