Cavity-enhanced rotational Raman scattering in gases using a 20 mW near-infrared fiber laser

Zhang

et al. 2021

Preprint

Gas sensors with high sensitivity, wide dynamic range, high selectivity, fast response, and small footprint are desirable across a broad range of applications in energy, environment, safety, and public health. However, designing a compact gas sensor with ultra-high sensitivity and ultra-wide dynamic range remains a challenge. Laser-based photoacoustic spectroscopy (PAS) is a promising candidate to fill this gap. Herein, we report a novel method to simultaneously enhance the acoustic and light waves for PAS using integrated optical and acoustic resonators. This increases sensitivity by more than two orders of magnitude and extends the dynamic range by more than three orders of magnitude, compared with the state-of-the-art photoacoustic gas sensors. We demonstrate the concept by exploiting a near-infrared absorption line of acetylene (C2H2) at 1531.59 nm, achieving a detection limit of 0.5 parts-per-trillion (ppt), a noise equivalent absorption (NEA) of 5.7×10-13 cm-1 and a linear dynamic range of eight orders of magnitude. This study enables the realization of compact ultra-sensitive and ultra-wide-dynamic-range gas sensors in a number of different fields.

Section: Resultsmentioning

confidence: 99%

Doubly resonant sub-ppt photoacoustic gas detection with eight decades dynamic range

Zhang

et al. 2021

Preprint

“…Fortunately, this intrinsic drawback can be overcome by reasonable experimental setups and design of structural parameters. One promising method is to combine HCFs with cavity enhanced Raman spectroscopy (CERS) to increase the laser intensity [87][88][89][90][91][92][93][94][95][96][97] (more details on CERS are presented in review [97]), as shown in Fig. 9a, in which the two FBGs act as highly reflective mirrors to form an F-P cavity.…”

Section: Raman Spectroscopy-based Fibre Gas Sensormentioning

confidence: 99%

Review of optical fibre sensors for electrical equipment characteristic state parameters detection

et al. 2019

Optical fibre sensing technology is a powerful method for long-term reliable sensing in harsh environments, which means it is particularly suitable for the detection of electrical equipment characteristic state parameters, including characteristic gases, abnormal vibration, ultrasonic produced by partial discharge, and abnormal temperature rise. This paper reviews several individual optical fibre sensors for different state parameters detection, discusses the advantages, limitations and possible improvement methods, and finally presents the most promising optical fibre sensor for each state parameter.

“…E.g., the CO 2 concentration is oftentimes inferred from the reading of a metal-oxide based, total volatile organic compound (TVOC) sensor, even though the correlation between TVOC and CO 2 is weak [15]. While Raman-based approaches may detect many gases simultaneously [16,17,18,19,20,21,22], techniques based on absorption spectroscopy are the most promising candidates for reliable CO 2 detection. Using tunable diode laser spectroscopy a high degree of sensitivity and specific, quantitative detection can be achieved, albeit at high associated costs in terms of optical and computational infrastructure as well as maintenance [23,24].…”

Section: Introductionmentioning

confidence: 99%

A Wireless Gas Sensor Network to Monitor Indoor Environmental Quality in Schools

Pérez

Bierer

Scholz

et al. 2018

Sensors

Schools are amongst the most densely occupied indoor areas and at the same time children and young adults are the most vulnerable group with respect to adverse health effects as a result of poor environmental conditions. Health, performance and well-being of pupils crucially depend on indoor environmental quality (IEQ) of which air quality and thermal comfort are central pillars. This makes the monitoring and control of environmental parameters in classes important. At the same time most school buildings do neither feature automated, intelligent heating, ventilation, and air conditioning (HVAC) systems nor suitable IEQ monitoring systems. In this contribution, we therefore investigate the capabilities of a novel wireless gas sensor network to determine carbon dioxide concentrations, along with temperature and humidity. The use of a photoacoustic detector enables the construction of long-term stable, miniaturized, LED-based non-dispersive infrared absorption spectrometers without the use of a reference channel. The data of the sensor nodes is transmitted via a Z-Wave protocol to a central gateway, which in turn sends the data to a web-based platform for online analysis. The results show that it is difficult to maintain adequate IEQ levels in class rooms even when ventilating frequently and that individual monitoring and control of rooms is necessary to combine energy savings and good IEQ.