Shiokawa Naoyuki, Tokunaga Eiji
Opt Express. 2016 May 30;24(11):11961-74. doi: 10.1364/OE.24.011961.
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.
通过将探测光束模式从零阶改变为准一阶厄米高斯（QHG）光束，提高了萨格纳克干涉仪光热偏转光谱的探测灵敏度。利用高阶HG模式的特性，即光束模式在传播过程中保持不变且场梯度增加，来提高测量灵敏度。在这种光谱学中，由于光热效应引起的横向光束偏转被灵敏地检测为干涉光强度的变化。由于QHG(1,0)光束在光电探测器处具有更高的场梯度，强度变化被放大。通过数值和实验证明了这种放大效应，使信噪比提高了两倍。
