Comprehensive three-dimensional ray tracing model for three-mirror cavity-enhanced spectroscopy

Abstract

A 3D ray tracing model is used to simulate optical reinjection in a nonresonant optical cavity, for off-axis integrated cavity output spectroscopy. The optical cavities are optimized for maximum intensity enhancement factors via a grid search and a genetic algorithm. Intensity enhancement factors up to 1400 are found for short cavities (3 cm) and up to 101 for long cavities (50 cm). The model predicts that short absorption cells can be used, having a long effective path length and a high throughput power. This opens new opportunities in the field of ultrasensitive absorption spectroscopy and allows the design of compact optical gas sensors.

Intensity enhancement in off-axis integrated cavity output spectroscopy

“…By using a re-injection mirror, the output intensity can be increased above the noise floor of the detector. From our model, it is shown that improved enhancements can be achieved by using shorter cavities with larger diameters [30]. This will trigger new opportunities in the field of ultrasensitive gas detection using compact optical gas sensors with a small footprint.…”

“…6). This might be due to the fact that distance between the re-injection mirror and the first absorption cavity mirror is equivalent to the focal length of the re-injection mirror [30]. At d ∕R 0.6, an ellipse consisting of 39 roundtrips (laser beam entrance angles α x −0.4°, α y −0.6°in the x, y direction) is found, which corresponds to a maximum enhancement factor of 38.…”

“…Recently, we developed a comprehensive three-dimensional ray tracing model to simulate optical re-injection using OA-ICOS [30]. We maximized the optical intensity throughput and absorption path length via a grid search and genetic algorithm.…”

“…In this paper, we experimentally verify this three-dimensional ray tracing model using a 30-cm-long absorption cavity. In addition, we used larger diameter re-injection mirrors to maximize the re-injection effect [30]. To demonstrate its usefulness for spectroscopy, we used a CO 2 absorption line in the near-IR wavelength region at 6240.10 cm −1 .…”

Long-Term Stable Online Acetylene Detection by a CEAS System with Suppression of Cavity Length Drift

“…By comparing the decay time of the empty cavity with that of the cavity filling with measured gas, the absorption coefficient can be obtained. Since the ring-down procedure occurrs in a fairly short period, CRDS highly depends on fast-response detection electronics, which limits its application [12,13]. Besides, the spectral resolution of CRDS is relatively low due to the use of pulsed lasers.…”