Improvement of the Detection Sensitivity for Tunable Diode Laser Absorption Spectroscopy: A Review

Abstract

Tunable Diode Laser Absorption Spectroscopy (TDLAS), a trace gas sensing technology based on infrared absorption spectroscopy, has been developed rapidly in the past few decades. The advantages of low cost and easy miniaturization could be applied in real-time monitoring. As an important factor, the detection sensitivity of TDLAS has been improved by a variety of methods. In this review paper, the important advances in TDLAS detection sensitivity are discussed, including the selection of absorption lines, the improvement of diode lasers, the design of effective optical paths, data demodulation, and the suppression of background interference. For gases with high application values, such as CH4, CO2, and NO, we summarize the detection sensitivity that the existing TDLAS system has been achieved, combined with the above-improved process. However, considering the principle of infrared absorption, the increase in detection sensitivity could reach an ultra-limit. Therefore, the hypothesis of the sensitivity limit of TDLAS is proposed at the end of the paper, through the quantization analysis.

Detection of NH3 in poultry housing based on tunable diode laser absorption spectroscopy combined with a micro circular absorption cell

“…The type of MCU is STM32F103. According to Beer-Lambert law [24], the gas concentration is proportional to the second harmonic amplitude, absorption line strength, optical path and pressure. At normal temperature and pressure, the absorption line strength, optical path and pressure are known and constant.…”

“…The measurement principle of TDLAS is based on Beer-Lambert law [24]. The detection sensitivity is often improved by increasing the effective absorption path at the same absorption line.…”

In situ detection of neodymium isotopes using tunable diode laser absorption spectroscopy for nuclear forensic analysis

“…Furthermore, the sensitivity has not been sufficiently considered despite its significance. Since the detection capability of an optical configuration could heavily depend on the sample and conditions, 15 the limit of detection should be systematically evaluated to confirm the feasibility. In addition, the signal enhancement method might be required to satisfy the desired performance for nuclear forensic applications.…”

Cantilever-enhanced photoacoustic spectroscopy for gas sensing: A comparison of different displacement detection methods

“…Chemical and semiconductor sensors are portable and cheap, but the stability, specificity and sensitivity are poor. Optical methods based on optical absorption detection, such as tunable diode laser absorption spectroscopy (TDLAS) [5] , cavity ring-down spectroscopy (CRDS) [6] and photoacoustic spectroscopy (PAS) [7] , [8] , [9] , [10] , [11] , [12] , [13] , have high sensitivity and sharp specificity. TDLAS and CRDS measure the attenuated laser energy by photodetectors after gas absorption.…”