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折射率是反映物质信息的重要物理量,在化学、生物、医药等领域中,经常需要将样品制成低浓度溶液进行化学或物理反应,通过对其折射率微小变化的检测来测定样品的各种性质及参数。为此,提出了一种利用表面等离子体共振传感原理测量液体介质折射率的激光相位测量方法,采用Kretschmann结构并建立模型。理论分析表明,在1.333~1.336的折射率变化范围内,反射光p、s分量相位差的变化与折射率变化呈近似线性关系,并由此得到测量公式。设计并搭建了基于双频激光外差干涉光路的折射率测量系统,系统具有良好的共光路结构,抗干扰能力强,信号处理采用相位调制方法,光路结构简单,测量精度较高。通过甘油溶液折射率测量实验表明其与理论分析结果一致,且与其他方法的结果吻合,两者的相互误差小于2.0×10-5。该方法可广泛应用于生物检测、化学分析、环境污染研究、医学诊断、食品卫生检测等领域。
Refractive index is an important physical quantity that reflects the material information. In the fields of chemistry, biology, medicine and the like, it is often necessary to make the sample into a solution of low concentration for chemical or physical reaction. The refractive index of the sample is determined by detecting the small change of refractive index Nature and parameters. For this reason, a laser phase measurement method using the surface plasmon resonance sensing principle to measure the refractive index of a liquid medium is proposed. The Kretschmann structure is adopted and a model is established. The theoretical analysis shows that within the range of 1.333 ~ 1.336 refractive index, the phase difference between the reflected light p and s components changes linearly with the change of refractive index, and the measurement formula is obtained. The refractive index measurement system based on the dual-frequency laser heterodyne interference optical path is designed and built. The system has a good common optical path structure, strong anti-interference ability, and the signal processing adopts the phase modulation method. The optical path structure is simple and the measurement accuracy is high. The measurement of refractive index of glycerol solution shows that it is consistent with the theoretical analysis, and the results of the other methods agree with each other, the mutual error of the two is less than 2.0 × 10-5. The method can be widely used in the fields of biological testing, chemical analysis, environmental pollution research, medical diagnosis, food hygiene testing and the like.