scholarly journals Dual Path Lock-In System for Elimination of Residual Amplitude Modulation and SNR Enhancement in Photoacoustic Spectroscopy

Sensors ◽  
2018 ◽  
Vol 18 (12) ◽  
pp. 4255 ◽  
Author(s):  
Qinduan Zhang ◽  
Jun Chang ◽  
Zhenhua Cong ◽  
Zongliang Wang ◽  
Fupeng Wang
Keyword(s):  
Amplitude Modulation ◽  
Photoacoustic Spectroscopy ◽  
Second Harmonic ◽  
Signal To Noise Ratio ◽  
Reference Signal ◽  
Distributed Feedback ◽  
Distributed Feedback Laser ◽  
Gas Concentration ◽  
Residual Amplitude Modulation ◽  
Lock In

A technique for elimination of residual amplitude modulation (ERAM) in photoacoustic spectroscopy based on dual path lock-in was proposed and experimentally demonstrated. There are two lock-in amplifiers, one is for gas concentration demodulation and another for residual amplitude modulation (RAM) measurement by tuning the reference signal in different phases, and then a dual path lock-in technique based on subtraction is applied to RAM removal, improving the second harmonic profile significantly. In this system, the signal to noise ratio (SNR) increases about two times based on our dual path lock-in technique compared to one distributed feedback laser diode (DFB-LD). The system achieved a good linear response (R-square = 0.99887) in a concentration range from 100 ppmv to 2400 ppmv and a minimum detection limit (MDL) of 1.47 ppmv.

Effect of Modulation Source Properties upon Signal-To-Noise Ratios of Inelastic Electron Tunneling Spectra

1986 ◽  
Vol 40 (8) ◽  
pp. 1180-1183 ◽  
Author(s):  
F. A. Dethomas ◽  
Cecil Dybowski ◽  
Harvey S. Gold
Keyword(s):  
Electron Tunneling ◽  
Second Harmonic ◽  
Signal To Noise Ratio ◽  
Harmonic Distortion ◽  
Inelastic Electron ◽  
Signal To Noise ◽  
Noise Ratio ◽  
Inelastic Electron Tunneling ◽  
Electron Tunneling Spectroscopy ◽  
Lock In

Lock-in amplification using ac modulation and second-harmonic detection is routinely employed in such techniques as ac polarography, ac voltammetry, and inelastic electron tunneling spectroscopy (IETS). Properties of the modulation source are shown in the present IET studies to limit the obtainable signal-to-noise ratio of a spectrum. A single inelastic electron tunneling junction is used to demonstrate the effect of various commercial modulation sources on the IET spectrum of benzoic acid on alumina. With all other parameters being held constant, the signal-to-noise ratio of the IET spectrum is found to be inversely correlated with the total harmonic distortion of the modulation source.

Optoelectronic oscillation of the second harmonic of a period-one oscillating distributed feedback laser

Optik ◽  
2019 ◽  
Vol 180 ◽  
pp. 313-317 ◽  
Author(s):  
Guangcan Chen ◽  
Dan Lu ◽  
Lu Guo ◽  
Wu Zhao ◽  
Yongguang Huang ◽  
...  
Keyword(s):  
Second Harmonic ◽  
Distributed Feedback ◽  
Distributed Feedback Laser

A Detection Circuit to Faint Signal for Difference Absorption Gas Sensor

2011 ◽  
Vol 128-129 ◽  
pp. 446-449 ◽  
Author(s):  
Yan Ju Wang ◽  
Jia Xing Chen ◽  
Yue Yi Kang ◽  
Li Kun Yang ◽  
Yu Tian Wang
Keyword(s):  
Background Noise ◽  
Signal To Noise Ratio ◽  
Reference Signal ◽  
Signal Frequency ◽  
Electric Signal ◽  
Signal To Noise ◽  
Detection Circuit ◽  
Measuring Signal ◽  
Lock In ◽  
Difference Absorption

ion: In gas difference absorption detecting system, the output electric signal is very faint and submerged in the background noise. In order to extract the faint signal covered by the background noise, we design the detective circuit aiming at how to restrain the noise and improve SNR of the system. In this paper, the detection circuit centering lock-in amplifier which reference signal frequency is automaticly followed is designed. The circuit adopts synchronization cumulating and locked loop technic, carries out frequency and phase aotomatic follow to the measuring signal by a locked loop circuit. The circuit not only avoids the tache taking reference signai from the modulator then adjusting the phase shif, but also improving signal-to-noise ratio more by synchronization cumulation.

Quartz enhanced photoacoustic spectroscopy with a 338 μm antimonide distributed feedback laser

2012 ◽  
Vol 37 (13) ◽  
pp. 2502 ◽  
Author(s):  
Mohammad Jahjah ◽  
Sofiane Belahsene ◽  
Lars Nähle ◽  
Marc Fischer ◽  
Johannes Koeth ◽  
...  
Keyword(s):  
Photoacoustic Spectroscopy ◽  
Distributed Feedback ◽  
Distributed Feedback Laser

scholarly journals Monolithic Double Resonator for Quartz Enhanced Photoacoustic Spectroscopy

2021 ◽  
Vol 11 (5) ◽  
pp. 2094
Author(s):  
Roman Rousseau ◽  
Diba Ayache ◽  
Nicolas Maurin ◽  
Wioletta Trzpil ◽  
Michael Bahriz ◽  
...  
Keyword(s):  
Photoacoustic Spectroscopy ◽  
Tuning Fork ◽  
Quartz Tuning Fork ◽  
Distributed Feedback ◽  
Acoustic Excitation ◽  
Distributed Feedback Laser ◽  
Water Vapor Absorption ◽  
New Approach ◽  
Vapor Absorption ◽  
Printing Techniques

A new approach for Quartz Enhanced Photoacoustic Spectroscopy is presented, based on an acoustic excitation from the outside of the prongs of a quartz tuning fork, to increase the sensitivity of the sensor. For this purpose, we introduce a monolithic acoustic double-resonator (double-mR) in a T-shape configuration, using 3D printing. It was modelized and experimentally characterized using a 1392 nm distributed feedback laser diode, targeting a water vapor absorption line. The setup showed a two-factor enhancement of the signal, compared to a classical off-beam QEPAS approach and confirmed the strong interest of photolithographic printing techniques for acoustic developments.

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