Poly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylene vinylene] (MEH-PPV) is a semiconducting optically active polymer widely used in optoelectronics research. MEH-PPV can be commercially acquired in a large range of molecular weights. However, the influence of this property on the optical performance of the polymer is often disregarded. In this paper, the thermal dependence of the refractive index of MEH-PPV thin films prepared from high and medium molecular weight polymers is investigated. Thus, monolithic Fabry-Perot (FP) microcavities are fabricated, in which the active polymer film is part of their defect layer. It is found that when these devices are used as optical temperature sensors, the position of the emission band of the microcavities excited with a blue diode laser shifts to lower wavelengths when temperature increases with sensitivities in the 0.2–0.3 nm/°C range. This effect is ascribed to the variation in the refractive index of the polymer active layer within the resonator with temperature. According to theoretical simulations of optical transmittance by classical transfer-matrix method and the evaluation of the optical eigenmodes by finite element methods of the manufactured FP resonator cavities, it is found that the MEH-PPV films present negative thermo-optic coefficients of about −0.018 K⁻¹ and −0.0022 K⁻¹ for high and medium molecular weight polymers, respectively, in the temperature range between 20 and 60 °C. These values are about the highest reported so far, to the best of our knowledge, and points to high performance thermal sensor applications.

聚[2-甲氧基-5-（2'-乙基己氧基）-1,4-亚苯基亚乙烯基]（MEH-PPV）是一种半导体光学活性聚合物，广泛用于光电研究。MEH-PPV可以大范围的分子量商购获得。然而，该性质对聚合物的光学性能的影响通常被忽略。本文研究了由高分子量和中分子量聚合物制备的MEH-PPV薄膜的折射率的热依赖性。因此，制造了整体式Fabry-Perot（FP）微腔，其中活性聚合物膜是其缺陷层的一部分。发现当这些设备用作光学温度传感器时，当温度以0.2–0.3 nm /°C范围内的灵敏度升高时，用蓝色二极管激光器激发的微腔的发射带位置会移至较低波长。这种影响归因于谐振器内聚合物活性层的折射率随温度的变化。根据经典传递矩阵方法对光透射率的理论模拟以及所制造的FP谐振腔的有限元方法对光本征模的评估，发现MEH-PPV膜的负热光系数约为-0.018 ķ对于高和中分子量聚合物，分别在20至60°C的温度范围内分别为^{− 1}和-0.0022 K ^{- 1}。就我们所知，这些值是迄今为止报道的最高值，并指出了高性能热传感器的应用。