Investigation On Property Of Photonic Crystal Microcavity And Application In Concentration Measurement Of Trase Gas

In recent years, the appearance of nanomaterials and fabrication for high-precisionplay important roles for thorough investigation of optical technique which leadsintegration optics to the hotspot. The optical microcavity is proposed and has significantplace in integration optics field. Some creative achievements emerge one after another. Inorder to investigate the properties of microcavity, we present a photonic crystalmicrocavity and calculate the emission characteristics. Furthermore, the application ofphotonic crystal defect microcavity in concentration measurement of trace gas isrepresented and proved experimentally.First of all, we introduce the metallic reflective film on both sides of photonic crystalslab. In consideration of the high reflectivity of metal in infrared region, the influence ofmetallic film on triangle lattice photonic crystal microcavity is analyzed. The variation ofair band located between the photonic crystal slab and metal has an effect on emissioncharacteristics of photonic crystal microcavity, such as resonant wavelength, quality factorand emission linewidth. Uniform distribution of field is achieved at the maximum qualityfactor which leads to the possibility of tunable photonic crystal laser.Secondly, KTP crystal is injected into the center of Si-substrate photonic crystal slabwith triangle lattice by which the defect microcavity is formed. We calculate the bandgapof photonic crystal microcavity with different radius of KTP using planar wave expansionmethod. The dependence of radius of KTP crystal on bandgap of photonic crystal isobtained.In addition, the concentration measurement system of trace gas based on fiber loopring-down method is proposed. The photonic crystal microcavity with KTP defect is fixedin the gas cell. According to the absorption wavelength in infrared region of interest gas,the signal light can pass through the photonic crystal microcavity with specular bandgaprange and the noise is prohibited.Finally, on the basis of photonic crystal microcavity, the experimental setup forconcentration measurement of trace gas is established. The performance tests of key elements in system are accomplished. The ring down time of trace gas at differentconcentration is received by the data acquisition system programmed by Labview. Thecorresponding fitting curve is plotted according to the data stored by personal computer.Moreover, the ring down curve of typical concentration is obtained theoretically by whichthe application of photonic crystal microcavity in concentration measurement of trace gasis proved.