Investigation of fast and sizeable photostriction effect in tellurium thin films using fiber Bragg grating sensors

We report a sizeable photoinduced strain in 90 nm tellurium (Te) thin film, coated on a fiber Bragg grating (FBG) sensor. The Bragg wavelength shift of the FBG sensor is used as the probe, to understand the photostrictive properties of Te thin film under illumination with laser light of visible wavelengths (405, 532 and 633 nm), at varying optical power density (5-161 mW/mm2), and also during cyclic exposure. An induced elastic strain of the order of 10−5 to 10−4 has been observed which is found to increase with increasing wavelength of laser illumination. The high (1 pm) resolution of the FBG interrogator used facilitates the accurate detection of the elastic strain induced in Te thin films even at a short exposure time of 0.1 s.