Quasi first-order Hermite Gaussian beam for enhanced sensitivity in Sagnac interferometer photothermal deflection spectroscopy

The detection sensitivity of a Sagnac interferometer photothermal deflection spectroscopy was enhanced by changing the probe beam pattern from zero-order to a quasi-first-order Hermite Gaussian (QHG) beam. The nature of the higher order HG mode, where the beam pattern is preserved during propagation...

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Veröffentlicht in:Optics express 2016-05, Vol.24 (11), p.11961-11974
Hauptverfasser: Shiokawa, Naoyuki, Tokunaga, Eiji
Format: Artikel
Sprache:eng
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Zusammenfassung:The detection sensitivity of a Sagnac interferometer photothermal deflection spectroscopy was enhanced by changing the probe beam pattern from zero-order to a quasi-first-order Hermite Gaussian (QHG) beam. The nature of the higher order HG mode, where the beam pattern is preserved during propagation with an increased field gradient, is utilized to enhance the measurement sensitivity. In this spectroscopy, the lateral beam deflection due to the photothermal effect is sensitively detected as a change in the interference light intensity. The change in intensity is amplified due to the higher field gradient of the QHG(1,0) beam at the photodetector. This amplification effect was both numerically and experimentally demonstrated to obtain twofold improvement in the signal-to-noise ratio.
ISSN:1094-4087
1094-4087
DOI:10.1364/OE.24.011961