Development of 3.0–3.45µm OPO laser based range resolved and hard-target differential absorption lidar for sensing of atmospheric methane

Gupta

et al. 2016

Spectroscopy Letters

We demonstrate a standoff system based on Quartz Enhanced Photoacoustic Spectroscopy technique for the concentration measurements of atmospheric ozone and methane. The technique is a modified version of Photoacoustic spectroscopy. Two primary features of this technique are the employment of a tunable Quantum Cascade Laser and a resonant Quartz-Crystal Tuning Fork detector. Both of these features facilitate, simultaneous sensing of multiple molecular species. External-cavity Quantum Cascade Laser having a spectral range from 7 to 10 micron is used. Diurnal concentration variations of methane and ozone are estimated for open-path up to 25 meters. The ambient methane and ozone concentration maxima were observed to have values of 3.5 parts per million by volume and 140 parts per billion by volume respectively. Finiteelement mesh based software is used to simulate the Eigen-frequency of the tuning fork sensor. High-resolution Transmission molecular spectroscopic database of atmospheric gases and the real-time gas concentration data from the Delhi Pollution Control Committee have been used as a reference.

Section: Resultssupporting

confidence: 92%

“…Optical parametric differential absorption LIDAR based measurements in 3.0 to 3.45 µm band have been carried out in our laboratory, and the daytime concentration of methane was observed to vary from 1.9 ppmv to 2.4 ppmv with root mean square deviation of 0.2 ppmv. [30] .…”

Section: Introductionmentioning

confidence: 99%

Open-path measurement of ozone and methane gases using quartz-enhanced photoacoustic spectroscopy

Gupta

et al. 2016

Spectroscopy Letters

“…The ratio of the backscattered received power at the OFF-wavelength and at the ON-wavelength can be used to assess the chemical species' concentration [12] and is given by the following equation where Δσ is the difference between the chemical's absorption cross sections for strong absorption at ONwavelength and weak absorption at OFF-wavelength. The powers at transmitted wavelengths & are assumed to be equal.…”

Section: Differential Absorption Lidar (Dial) Systemmentioning

confidence: 99%

Differential absorption LIDAR signal denoising using empirical mode decomposition technique

Jindal,

Mainuddin,

Veerabuthiran

et al. 2023

Opt Quant Electron

Self Cite

Differential Absorption Lidar (DIAL) technique is a potential method for the remote detection of hazardous chemicals in the atmosphere. These hazardous chemicals can be due to industrial pollution or may be intentionally released by the terrorist groups or military forces of the enemy country to endanger both the military's personnel and the civilian population's lives. DIAL technique may be used for probing such chemicals from far-off distances of several km ranges and generating an early warning for the response teams. The output of the DIAL system normally consists of three parameters viz. name/class of hazardous chemical detected; its location in terms of distance and the concentration. The maximum standoff distance capability for any Lidar system depends on the signal to noise ratio which is governed by the parameters like atmospheric conditions, Lidar subsystem speci cations, noises, etc. SNR is often limited by several noises embedded in the signal from various sources. Due to the presence of noises in the signal, the errors are introduced in the concentration estimation of chemicals from Lidar signal. The methods for improvement of SNR of lidar signal has been often limited by application of conventional denoising techniques like multi-pulse temporal averaging and spatial averaging and further requires nonlinear techniques for noise reduction due to nonlinear behavior of lidar signals. In the present work, Empirical Mode Decomposition (EMD) technique has been implemented on the Lidar signal from Differential Absorption Lidar system. The signal has been denoised and improved SNR is compared with that achieved from temporal averaging and spatial averaging. It was observed that the EMD technique is a better technique as compared to other conventional techniques like multi-pulse temporal averaging and spatial averaging for denoising the signal and increasing Lidar SNR. It is seen that SNR can be improved 4-5 times the original SNR using EMD technique.

“…Near-/mid-IR DIAL lidars presented in [20][21][22] can be attributed to the instruments for the laser gas analysis. In work [23], development of 3000-3450 nm OPO laser-based range resolved and hard-target differential absorption lidar for sensing of atmospheric methane is presented.…”

Section: Introductionmentioning

confidence: 99%

Remote Sensing of Atmospheric Methane with IR OPO Lidar System

et al. 2020

A differential absorption lidar (DIAL) system designed on the basis of optical parametric oscillators (OPO) with nonlinear KTiOAsO4 (KTA) and KTiOPO4 (KTP) crystals is described. The crystals allow laser radiation tuning in the infrared region (IR) wavelength region. The measurements in the 3.30–3.50 μm spectral range, which includes a strong absorption band of methane, are carried out. Lidar backscattered signals in the spectral band 3.30–3.50 μm has been measured and analyzed along the horizontal path in the atmosphere. Based on the experimental results, CH4 concentrations ~2.085 ppm along a 800 m surface path are retrieved in the spectral range under study with a spatial resolution of 100 m.