Reduction of residual amplitude modulation in frequency-Modulation spectroscopy by using harmonic frequency modulation

Edward A. Whittaker, Chi Man Shum

Research output: Contribution to journalArticlepeer-review

40 Scopus citations

Abstract

A new technique to improve the sensitivity of frequency-modulation laser absorption spectroscopy is reported.Theoretical analysis and experimental demonstration show that the application of two harmonically related, appropriately phase-shifted rf waves to the electro-optic modulator can reduce the residual amplitude-modulation background signal in the photodetector output current without reducing the absorption-induced signal. When the new method was used, the residual amplitude-modulation background was reduced by a factor of 4. Our results suggest that shot-noise-limited detection sensitivity may eventually be achieved without using dual-beam compensation or dc-biased modulators.

Original languageEnglish
Pages (from-to)1253-1256
Number of pages4
JournalJournal of the Optical Society of America B: Optical Physics
Volume5
Issue number6
DOIs
StatePublished - Jun 1988

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