采用有机/无机混合溶胶-凝胶法制作条形光波导,并将条波导接入光纤Sagnac 环中,测量了输出光功率随环境气氛中乙醇蒸气体积分数变化的特性,表明在实验研究的范围内,输出信号与乙醇蒸气体积分数呈正弦变化。根据Sagnac环结构输出特性的基本关系,反映了溶胶-凝胶条波导在乙醇蒸气气氛下产生了双折射效应。观察到双折射相移与乙醇体积分数的亚线性关系。对实验数据拟合,计算了偏振相移的线性项和二次项系数,得到所制备的条波导的双折射对乙醇体积分数的响应为Δn≈4.4×10-2。测量了信号变化的时间演变特性,典型的上升和下降时间常数分别为3 min和12 min。

A stripe waveguide was fabricated by organic-inorganic hybrid sol-gel technology. The waveguide was connected into a Sagnac fiber loop to measure output power under environment of different ethanol vapor volume fraction. It was found that the output signal varied in a sinusoidal function of ethanol vapor volume fraction within the measured range. According to the property of Sagnac loop, the measured behavior indicates that there exists birefringence caused by ethanol vapor absorption into the sol-gel material. The birefringence phase shift was observed to vary with ethanol vapor volume fraction in a sub-linear way. The coefficients of the linear term and second order term were calculated from the experimental data fitting, and the birefringence sensitivity to ethanol volume fraction was evaluated to be Δn≈4.4×10-2. The temporal signal change was also measured, and the typical rising and falling time constants were obtained to be 3 min and 12 min respectively.