Title :
Elimination of residual amplitude modulation in TDLS-WMS
Author :
Chakraborty, Arup Lal ; Ruxton, Keith ; Johnstone, Walter ; Duffin, Kevin ; Lengden, Michael
Author_Institution :
Dept. of Electron. & Electr. Eng., Univ. of Strathclyde, Glasgow, UK
Abstract :
Tunable diode laser spectroscopy with wavelength modulation (TDLS-WMS) has long been plagued by the problem of residual amplitude modulation (RAM) that limits the sensitivity in 1st harmonic detection. To circumvent the problem 2f-detection has been the common electronic signal recovery approach. However, in such systems, absorption lines cannot be recovered directly, and they require calibration. To date, no method has been devised to eliminate the RAM at the optical level. We present, for the first time, a fiber-optic technique that eliminates the concentration-independent RAM component and allows 1f calibration-free recovery of gas absorption lines. The technique is stable and can be readily modified for a real-time and automated system.
Keywords :
amplitude modulation; modulation spectroscopy; optical fibres; optical modulation; semiconductor lasers; RAM; TDLS-WMS; calibration-free recovery; concentration-independent RAM component; fiber-optic technique; gas absorption line; harmonic detection; real-time system; residual amplitude modulation; tunable diode laser spectroscopy; wavelength modulation spectroscopy; Absorption; Amplitude modulation; Calibration; Diode lasers; Intensity modulation; Optical fiber couplers; Optical modulation; Photonics; Spectroscopy; Tunable circuits and devices;
Conference_Titel :
Lasers and Electro-Optics 2009 and the European Quantum Electronics Conference. CLEO Europe - EQEC 2009. European Conference on
Conference_Location :
Munich
Print_ISBN :
978-1-4244-4079-5
Electronic_ISBN :
978-1-4244-4080-1
DOI :
10.1109/CLEOE-EQEC.2009.5196266