激光束照射液体产生的热累积效应会引起其折射率变化，从声光方程出发分别分析了液体瞬态折射率与稳态热致折射率产生的机理，研究了透镜焦距以及入射波长对去离子水折射率的影响。利用表面等离子体共振检测系统对温度改变的高度敏感性，建立了一种新型的液体棱镜检测系统，数值模拟了不同功率下去离子水的稳态共振曲线，当功率变化为0.7 W时，其折射率变化为1.4×10-3。采用功率可调的980 nm的连续激光器对去离子水的热光效应进行了实验研究，得到了其稳态热致折射率随功率的变化关系，当功率变化0.7 W时，其折射率变化为3.35×10-3，最后剖析了实验与理论之间误差的可能来源。

The thermal accumulative effect of liquids induced by laser illumination gives rise to the refractive-index change. On the basis of photo-acoustic equations, the mechanism on the transient-state and steady-state thermal indexes of the liquids can be analyzed, respectively. Moreover, the effects of the incident wavelength and focal length on the refractive index of deionized water are studied. Using surface plasmon resonance detection system that is highly sensitive to temperature alteration, an original liquid prism detection system is set up, and the resonance curve of the deionized water at various power levels is numerically simulated from which refractive-index change of 1.4×10-3 in the case of power change of 0.7 W is obtained. Then the experimental researches on thermo-optical effect of the deionized water are carried out by means of continuously operating laser of 980 nm wavelength with adjustable power levels, and the dependences of steady-state thermal index on different power levels are obtained. It is observed that the refractive-index change reach 3.35×10-3 when power change is 0.7 W. Finally, possible error sources between the experimental results and the theoretical simulation are discussed.