光子晶体光纤有源内腔气体传感研究-光电子技术专业论文.docxVIP

ABSTRACT In industry, it’s important to detect flammable and explosive gas (like C2H2、 NH3 and CH4). So, optical fiber sensing technology appears, and it has many advantages like smaller volume、the ability of anti-electromagnetic and facility of distributed sensor. Active intra-cavity gas sensor with photonic crystal fiber has become a hot area of research because in such a system the area of gas touching optic is largely enhanced; optic can be sufficiently absorbed by gas and detection sensitivity is obviously increased. This thesis is based on active intra-cavity gas sensor with photonic crystal fiber. Main points are as follows: We design a new hollow-core photonic crystal fiber, of which the diameter of small ventages is 2.4μ m, pitch of adjacent ventages is 3.8μ m, and diameter of core is 11μm. Then we set wavelength of the fiber at peak absorption of C2H2 and NH3 (1530nm and 1967nm) to carry out numerical calculation employing COMSOL Multiphysics finite element software, and the relative sensitivity coefficient is above 0.95. We also simulate the effect of ventage diameter and efficient mode refractive index on relative sensitivity coefficient at wavelength of 1530nm and 1967nm. Base on the analysis above, we can conclude that the detection sensitivity of C2H2 and NH3 can be enormously enhanced using this PCF. We simulate the effect of intra-cavity loss on output power at different coupling ratio and as well as the effect of pump power on relative sensitivity enhancement coefficient. At last, we get the conclusion that the higher coupling ratio is, the lager relative sensitivity enhancement coefficient is and when laser works around the threshold the sensitivity is much higher than other conditions. In addition, we verify the conclusion in experiments and get the good coherence. In experiments, we compare the intra-cavity absorption and outside cavity absorption. When we fill a gas cell in which PCF is tangled with 0.2MPa gas, and put the cell out