Thermally actuated interferometric sensors based on the thermal expansion of transparent elastomeric media

In this article the fabrication and characterization of two thermally actuated optical devices for the measurement of temperature and power are described. A transparent polymer having a high coefficient of thermal expansion—poly(dimethylsiloxane) (PDMS)—was used as the temperature-sensitive medium. Changes in the dimensions of the polymer on heating caused the observed optical responses of both devices. The temperature sensor based on the Fabry–Pérot cavity measures temperature differences to a precision of 0.005 °C within the linear working ranges of the device. The power sensor uses the architecture of a Mach–Zender interferometer; it is suitable for measurements of powers in the mW/cm2 range, delivered optically to the surface of the device in the visible wavelength region. The devices are inexpensive, easy to fabricate, and mechanically rugged. They offer alternatives to other sensors for measuring temperature and power.