Investigations on photo-mechanical and photo-thermo-mechanical strain variations in amorphous selenium using fiber Bragg grating sensor

Light-induced structural changes are investigated on 90 nm thick amorphous-selenium (a-Se) thin film, coated on the cladding layer of an optical fiber Bragg Grating (FBG) sensor, upon illumination with 532 nm laser of 10 mW/mm2 power under different exposure times (ms, s, min, h). The changes induced are measured using the photo-induced strain produced. In the present experiments, the contributions of photo-mechanical and photo-thermo-mechanical effects have been well separated. Also, the photo-thermally induced crystallization effects on the magnitude of the photo-induced strain have also been investigated.