In-situ measurement of vapor cell temperature based on obliquely incident pump light for NMR sensors.

This paper presents a pump-light-based in-situ temperature measurement method for nuclear magnetic resonance (NMR) vapor cells under oblique optical incidence. To miniaturize the NMR sensor, a thin vapor cell is employed, in which both the orthogonal pump and probe light are introduced obliquely through one surface of the vapor cell. A model is developed to relate pump-light absorption to Rb atomic density, thereby enabling inference of the vapor cell temperature. The model includes polarization distortion, polarization-dependent window transmission attenuation, effective optical path length, and the coupling between optical absorption and atomic polarization. Experimental results show that the proposed method achieves the lowest RMSE of 0.179 K and reduces it by at least 68.2% compared with several commonly used fitting methods, enabling accurate in-situ temperature measurement in miniaturized NMR sensors under obliquely incident pumping.