Sensitive detection of HO2 radicals produced in an atmospheric pressure plasma using Faraday rotation cavity ring-down spectroscopy

Abstract

A scalable arbitrary waveform generator for atomic physics experiments based on fieldprogrammable gate array technology Review of Scientific Instruments 90, 043101 (2019);

Optical activity of lysozyme in solution at 532 nm via signal-reversing cavity ring-down polarimetry

“…An expansion of the standard polarimetric methods came with the introduction of Cavity Ring Down Polarimetry (CRDP) by Vaccaro and co-workers in the early 2000s [10], which used a linear optical cavity to enhance polarimetric signals, and has produced a variety of optical rotation measurements in the gas and liquid phase [11,12,13,14,15,16]. Linear cavities have also been used to measure the Faraday Effect in gases [17,18,19]. In 2014, our group improved CRDP by using a ring cavity, allowing counter-propagating laser beams, and an intracavity Faraday Effect.…”

Continuous-Wave Cavity Ring-Down Polarimetry

“…In particular, Westberg and Wysocki 59 using an optical cavity with F ≈ 50000 demonstrated Faraday optical rotation sensitivities of ∼ 1.3 × 10 −9 rad/ √ Hz (per cavity round-trip, for 1 s of integration time), at 762 nm. Similarly, Gianella et al 32 using an optical cavity with F ≈ 175000, demonstrated almost identical Faraday optical rotation sensitivities of ∼ 1.24 × 10 −9 rad/ √ Hz (per cavity round-trip, for 1 s of integration time), at 1506 nm. Using our analysis on the fundamental frequency sensitivity limits of CRDP ("Prediction" point in Fig.…”

“…We start by discussing the theory of CW-CRDP. Although several extended analyses of the theory behind CW-based cavity-enhanced polarimetric schemes exist in the literature 32,[39][40][41] , we repeat here key theoretical aspects to clarify the necessary terminology and concepts required to understand the experimental principles of the CW-CRDP technique.…”

“…PD-CRDS schemes have achieved nearshot-noise limited sensitivities at < 10 −9 rad √ Hz levels, and have been employed for measurements of linear and non-reciprocal circular birefringent effects, such as the measurement of residual or stress-induced linear birefringence of supermirrors [25][26][27][28] , and the measurement of resonant Faraday optical rotation (otherwise known as FR-CRDS) as employed for the sensitive and selective detection of paramagnetic gaseous molecules and radicals (e.g. O 2 [29][30][31][32] , HO 2 32,33 ). However, PD-CRDS is specifically suitable for resonant effects and requires ultrahigh finesse optical cavities (as the sensitivity in the decay time is translated directly into polarimetric sensitivity), which effectively increases the cost of the apparatus and can limit its operational lifetime (degradation of the high quality optical mirrors results in reduced sensitivities), precluding this approach from being the most suitable one for portable instrumentations for field studies.…”

Simultaneous determination of transient free radicals and reaction kinetics by high-resolution time-resolved dual-comb spectroscopy

“…Although the sensitivity of current system for HO 2 detection is lower than that attained in experiments using cavity ring-down spectroscopy in the near infrared region 37,38 , the sensitivity of the adopted method can be improved by coupling the dual-comb laser with a cavity-enhanced reaction cell.…”