Research On Near Infrared Gas Sensing Hollow Core Waveguide And It's Application

Due to the increasing demand of environment monitoring, gas monitor is playingmore and more important role in human living. Near infrared spectrum is one of themost popular methods in gas sensing, due to the advantage of good selectivity, simpleand quickly test process, no broken and small sample requirement. In gas sensingfield, spectrum method have low sensitivity because of low absorption of gas. Longinteraction length is usually needed in gas sensing. Many new techniques have beenintroduced in to spectrum method to improve the sensitivity, in which hollow corewaveguide and white cell are the most successful methods. Compare to white cell,hollow core waveguide has simple structure, long interaction length, low cost andgood bending capability. So hollow core waveguide have become a most potential gassensing method.Hollow core waveguide have been successfully used in gas sensing and manyachievements in scientific research have been made in infrared spectrum. But in nearinfrared field, hollow core waveguide are seldom used due to the large losses. In thistext, based on the analyze of the history, the category and the detecting theory ofhollow core waveguide, we advance a new concept that gas sensing hollow corewaveguide specially use in near infrared. This guide has an attenuated totalreflectance structure and Ag has been selected as the film material. We haveexperiment the deposition of Ag film and a best condition has been achieved. Thenthe copper has been introduced in hollow core waveguide, which extend the filmmaterial. For the sake of improve the test efficiency in unit length in hollow corewaveguide, another technique has been introduced for the fist time, which isstationary liquid in gas chromatography technology. A new hollow core waveguidestructure, which is liquid film hollow core waveguide, has been taken out. This liquidfilm can dissolve the gas molecules and then increase the concentration of gas inhollow core. This method has been found an important effect on gas sensingespecially low concentration gases. Finally, we develop a near infrared gas sensingequipment using hollow core waveguide. This equipment is a miniaturization gas sensing equipment which is meaningful for the rapid gas detection.