Mid-infrared cavity ring-down spectroscopy using DFB quantum cascade laser with optical feedback for radiocarbon detection

Abstract

A linewidth reduction of a distributed feedback quantum cascade laser (DFB-QCL) based on optical feedback for a mid-infrared (MIR) cavity ring down spectroscopy (CRDS) 14C spectrometer is presented. A cat-eye reflector as well as a path-length enhancement by a Herriott cell were employed for a compact optical setup. The laser linewidth was evaluated by monitoring the beat frequency between the DFB-QCL and a MIR optical frequency comb (OFC). The linewidth reduction by optical feedback was clearly observed although slow frequency drifts caused by environmental changes were still visible. A low-bandwidth beat-note lock to the OFC was conducted for long-term stabilization as well as for precise frequency scanning and thereby 14C measurement by MIR CRDS with optical feedback was demonstrated successfully.

Room-Temperature Optical Detection of 14CO2 below the Natural Abundance with Two-Color Cavity Ring-Down Spectroscopy

“…2C-CRDS’s room-temperature detection of 14 CO 2 below the natural abundance is unique among other cavity-enhanced 14 CO 2 measurement techniques that all require cryogenic test gas cooling. The accuracy presented here (8% of the natural 14 C abundance in 3 min) improves upon cryogenic linear-absorption CRD methods with accuracies greater than 10%. ,− Like 2C-CRDS, Saturated Absorption Cavity Ring-Down Spectroscopy (SCAR) actively compensates for variations in the cavity base loss. Under cryogenic cooling at 170 K, SCAR achieved an accuracy of ∼1% of the natural abundance in a 100 min averaging time .…”

“…Cavity ring-down (CRD) spectroscopy has emerged as a viable 14 C detection technique. − It utilizes strong antisymetric-stretch band (ν 3 ) transitions of 14 CO 2 in the mid-IR and has demonstrated parts-per-quadrillion (ppq) precisions ( 10 − 15 C 14 C ) , which are well below the natural abundance (i.e., 1.2 × 10 − 12 .1em normalC 14 normalC ). , A high-finesse, optical cavity that is centimeters long can provide gas–laser interaction path lengths equivalent to kilometers. This cavity-enhanced path length increases the total gas absorption sensitivity, but this enhancement is not selective to the target analyte alone.…”

Development of 2.2 μm cavity ring-down spectrometer for tritiated water analysis

“…In our previous study, frequency stabilization of the DFB diode laser based on optical feedback has been developed for highly sensitive 14 C detection with CW-CRDS and a single detection limit of 1 × 10 −9 cm −1 Hz −1/2 and a reachable detection limit in 10 s measurement (acquisition rate of approximately 55 signals s −1 ) of 5 × 10 −11 cm −1 was demonstrated. 9,27) If systematic fluctuations can be controlled for 600 s with the acquisition rate of 10 2 signals s −1 , the required sensitivity can be achieved. In addition, since absorption line intensities in the 4 μm region are around one order of magnitude larger than those in the 2 μm region, further improvement in sensitivity could be expected by transitioning to that wavelength region.…”

Cavity Ring-Down Spectroscopy: Recent Technological Advancements, Techniques, and Applications

“…The measurements of CRDS agreed quiet well with the results of LSC, except slight differences in urine samples arising from the uncertainties in the analysis and actual metabolism differences of the individual rats. In a recent study, 122 the group modified the mid-IR CRDS spectrometer for better frequency stabilization. They designed an optical feedback system consisting of a "cat-eye" reflector and Herriot cell configuration for improved line width reduction of DFB-QCL and subsequently utilized a low-bandwidth beat-note system lock to a mid-IR OFC for the long-term stabilization and precise frequency scanning.…”