Temperature test of photorefractive materials using light speed slowdown method

摘要

In the paper, we propose one new type sensor with light modulation method. Having learned to delay a light signal by means of optical fibers, the temperature field may be detected by this way. According to the light speed which can be modulated in a photorefractive material in which written steady volume-index grating by two laser beams in opposite direction, the light signal may transmit with phase modulating due to intervening of another frequency shifting laser beam. In the experiment, the inner grating would be written in an optical fiber in which suitable Stannum has been doped. The periodic structure in the fiber can make the light signal reflect and the value of phase shift corresponds to the effective length of the periodic grating. According to magneto-optical Faraday effect, temperature may changes polarization direction by shifting Verdet constant. During testing period, a Sn-doped fiber is exposed to measured temperature environment and certain uniform steady field. Under this environment, the more the temperature increases, the shorter the effective interference area is in the fiber. Comparing with light delayed signal that transmits through fiber with different temperature, the delaying value may be corresponded to temperature. This research work is supported by the National Natural Science Foundation of China under grant No.60472023.