Residual amplitude modulation method implemented at the phase quadrature frequency of a 1650nm laser diode for line shape recovery of methane

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dc.contributor.author Upadhyay, Abhishek
dc.contributor.author Chakraborty, Arup Lal
dc.date.accessioned 2014-10-21T13:07:54Z
dc.date.available 2014-10-21T13:07:54Z
dc.date.issued 2015-02
dc.identifier.citation Upadhyay, Abhishek and Chakraborty, Arup Lal, "Residual amplitude modulation method implemented at the phase quadrature frequency of a 1650nm laser diode for line shape recovery of methane", IEEE Sensors Journal, DOI: 10.1109/JSEN.2014.2358714, vol. 15, no. 2, pp. 1153-1160, Feb. 2015. en_US
dc.identifier.issn 1530-437X
dc.identifier.uri http://dx.doi.org/10.1109/JSEN.2014.2358714
dc.identifier.uri https://repository.iitgn.ac.in/handle/123456789/1450
dc.description.abstract This paper reports the extraction of concentration and pressure of methane using a 1650nm laser diode operated at its phase quadrature frequency (fq) and using the calibration-free residual amplitude modulation (RAM) method. Although the RAM method is the simplest calibration-free technique it has low signal levels compared to the Phasor Decomposition (PD) method for small values of the phase difference between the laser intensity modulation (IM) and frequency modulation (FM). For the laser diode used in this studyturned out to be 90° at a very modest modulation frequency of 125.5 kHz which is an order of magnitude lower than values reported elsewhere. The RAM signal and the FM signal are at phase quadrature at this frequency and each can be fully and simultaneously recovered along a detection axis of a lock-in amplifier free from distortion by the other. The absolute absorption profile is accurately recovered with the signal to noise ratio maximized for this laser. The gas parameters are extracted by fitting a Voigt line shape to the experimental data. These results show that when operating at fq, the PD method offers no advantage over the RAM method and is therefore redundant. In addition, the background RAM is eliminated by an automatic fiber-optic RAM nulling technique. Finally the RAM method is also implemented at high values of modulation index to increase the signal-to-noise ratio. The time resolution of measurements is currently 10s.The prospect of using the RAM method with a 2004nm VCSEL is also explored. en_US
dc.description.statementofresponsibility by Abhishek Upadhyay and Arup Lal Chakraborty
dc.format.extent Vol. 15, No. 2, pp. 1153-1160
dc.language.iso en en_US
dc.publisher IEEE Xplore en_US
dc.subject Absorption en_US
dc.subject Frequency modulation en_US
dc.subject Laser tuning en_US
dc.subject Random access memory en_US
dc.subject Shape en_US
dc.subject Vertical cavity surface emitting lasers en_US
dc.title Residual amplitude modulation method implemented at the phase quadrature frequency of a 1650nm laser diode for line shape recovery of methane en_US
dc.type Article en_US
dc.relation.journal IEEE Sensors Journal


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