Temperature sensor with microstructure fiber based ruby fluorescence lifetime

Hollow core bandgap microstructure fiber was used to make a probe of temperature sensor based ruby fluorescence lifetime. Fiber-optic temperature sensors using a fluorescent lifetime of ruby crystal are regarded as useful thermometer due to its wide dynamic range, intrinsic immunity to electromagnetic interference, small size, and calibration-free measurement. It often be used under extraordinary conditions. In these thermometer, a ruby crystal as sensor head is connected mechanically with the silica fibers or the sapphire fibers, or grown from the melt droplet on the end of the sapphire fibers. In this paper, microstructure fiber was used to make a temperature sensor probe based fluorescent lifetime. To avoid the redistribution of the photoluminescence, a small size ruby crystal with Cr³⁺ concentration of 0.35at.% was made as a rod (with diameter 60 micron and 2 millimeter long) and was inserted to the air-core of the microstructure fiber at one end. The ruby rod was fastened in the hole by optical adhesive. The ruby crystal cylinder was plated with silver on its surface except the top side. The silver plating can hold the fluorescent light in the crystal and fiber to enhance the intensity of the week fluorescence signal, prevent stray light coming into the probe. Compared with the conventional optic-fiber temperature sensor, the microstructure fiber sensor based ruby fluorescence lifetime sensor has more advantages: such as larger dynamic range, higher precision and resolution, smaller size, and so wider applying region.