[7a-PA5-1~22] 3.8 Optical measurement, instrumentation, and sensor

[7a-PA5-21] Crosstalk from intensity noise to phase noise in noise cancellation method by phase detection method for pump/probe spectroscopy and its countermeasure

〇Keisuke Seto¹, Takashi Tarumi¹, Eiji Tokunaga¹ (1.Tokyo Univ. Sci.)

Keywords:noise cancel, spectroscopy, stimulated Raman

In the pump/probe measurement, the intensity noise of the probe light source determines the signal to noise ratio (SNR). We have developed the noise cancellation technique for a repetitive pulse light source. The intensity modulation of the probe in a sample measurement is converted into a pulse repetitive phase change independently of the intensity noise and detected on the phase detection. However, there is a crosstalk between the intensity and phase at a photodetector and detection circuit. This crosstalk causes transformation of the intensity noise into the phase noise, which limits the SNR modification. We also discuss cancellation methods for the crosstalk.