Ultimate sensing resolution of water temperature by remote Raman spectroscopy

Abstract

The limit of sensing resolution of water temperature by remote Raman spectroscopy was investigated experimentally. A remote Raman spectrometer, which employed a telescope of 20 cm in pupil size and the second harmonic generation (SHG) of a Q-switched Nd: YAG laser, was used for the measurement. By analyzing the broad O-Hstretching Raman band located near 3500 cm(-1), a parameter which is in secondorder polynomial relation with water temperature from 13 degrees C to 50 degrees C could be obtained. The resolution of our remote Raman temperature sensor was better than +/- 0.2 degrees C with measurement time shorter than 10 s. The influence of the Raman signal's signal-to-noise ratio on the resolution and salinity effect on the accuracy of temperature sensing were also investigated. (C) 2015 Optical Society of America