Sensing with optical vortices in photonic-crystal fibers

We demonstrate optical polarization vortex generation in a photonic-crystal fiber (PCF) by means of a CO2 laser-induced long period grating. Vortices are a special subclass of fiber modes that result in polarization-insensitive resonances even when grating perturbations are asymmetric, as is the case with structural perturbations in single-material PCFs. The physics of vortex generation, combined with the use of structural perturbations alone, in single-material fibers, opens up a new schematic for realizing harsh-environment sensors. We show that the temperature and polarization stability of our vortex devices is maintained for prolonged periods of time (tested up to 34 h) at temperatures exceeding 1000 degrees C. We envisage that this demonstration opens up a new way of realizing high-temperature sensors in a cost-effective manner. (C) 2012 Optical Society of America