Photonic Crystal Fiber Tip Sensor for High-Temperature Measurement

We demonstrate a temperature sensor consisting of a 2-D, Silicon (Si), Photonic Crystal (PC) attached to the facet of a standard single-mode optical fiber. The 2-D PC sensors are fabricated on standard Si wafers, using a single mask and a combination of isotropic and anisotropic etching, and microassembled onto the facets of the optical fibers by Si-welding. The temperature of the Si-PC sensor is monitored by measuring its reflectance spectrum in the 1250 to 1650 nm wavelength range. The measured reflectivity peak shift is 0.11
${\rm nm}/^{\circ}\hbox{C}$
in the 100
$\ ^{\circ}\hbox{C}$
to 700
$\ ^{\circ}\hbox{C}$
temperature range. The observed spectral shift and temperature sensitivity are significantly higher than high-temperature fiber Bragg grating sensors, and comparable to long-period fiber gratings sensors. The high sensitivity, combined with compactness and robust structure, give these sensors strong potential for use in harsh environments.