Font Size: a A A

Micro-nano Optical Fiber Gas Sensing Properties, Carbon Nanotubes Thin Film Research And The Analysis Of Mode Field

Posted on:2013-01-26Degree:MasterType:Thesis
Country:ChinaCandidate:L JiaFull Text:PDF
GTID:2248330374986697Subject:Optical Engineering
Abstract/Summary:PDF Full Text Request
In recent years, with the demand of miniaturization of electronic and photonicdevices, nano-materials and micro-nano optical waveguide are being developed rapidly.Because of its large proportion of the evanescent wave, small size, simple preparationand low loss, Micro-nano fiber has been widely used in the field of photonics. Usingmicro-nano fibers as the basic structures of the optics, we can fabricate integratedoptical waveguide with smaller size and more simply operation and lower insertionloss than conventional ones. Micro-nano fiber-optic devices include micro-nanoMach-Zehnder interferometers, micro-ring resonant cavities and saturable absorbers. Inthis paper, typical micro-nano fiber-optic structures and relevant applications arebriefly introduced.Since1991Iijima discoverd the carbon nanotubes, they have been regarded as themost promising nanomaterials in21st century. According to the numbe of layers ofgraphene, carbon nanotubes are divided into Single-walled nanotubes and Multi-walledones and we select the former in our experiments. Carbon nanotubes have not only theideal one-dimensional model and huge length-diameter ratio, but also excellentelectrical, mechanical and chemical properties. Therefore, they have good prospects inthe fields of molecular electronics, nanoelectronic, composite materials, optics.Based on LB coating technology, we make up a novel structure by depositingcarbon nanotubes onto the surface of the micro-fibers, and study its gas sensingproperties as well as mode field characteristics. The main works and contents of thispaper include the following aspects.Firstly, We introduce the characteristics and preparation methods of micro-nanofiber. According to the main preparation methods reported, we select a simple methodfor laboratory operation A standard optical fiber is heated to a molten state byKerosene lamp, and the molten portion is stretched uniformly by moving the free endof the fiber. In this way, we obtain micro-fibers with uniform and smooth surface,which meet the needs of our experiment.Secondly, We studied the preparation methods of carbon nanotube filming micro-fiber. Carbon nanotubes were dissolved in chloroform and at the same time thedispersive solution was prepared by the ultrasonic mechanism. Then, by use of the LBcoating technology, carbon nanotubes were uniformly deposited onto the micro fibersurface. Our experiments demonstrate that high-quality carbon nanotubes filmingmicro-fibers can be obtained with the improvement of coating process and experimentsettings.Next, We theoretically analyze the gas sensing principle of carbon nanotubefilming micro-fiber through modeling and numerical simulation. When used the carbonnanotube filming microfiber as a gas sensor, We analyze the mechanism of carbonnanotube film with gas molecules, and also found the relationship between theintensity of output light and dielectric constant as well as the absorption coefficient,respectively. Based on the theory of evanescent field of a round fiber, and consideringthe influence of the deposition of multilayer films, We analyzed mode fieldcharacteristics of thin-filming microfiber by Matlab.At last, We researched the optical properties of the carbon nanotubes filmingmicrofiber by experiment. we measured the output intensiy of carbon nanotubesfilming microfiber in the gas environment and found that the gas concentration and thenumber layers can influence the output light intensity. next, we used the mode fieldanalyzer to observe the mode field characteristics of microfiber. Energy distribution ofuncoated microfiber and carbon nanotubes filming microfiber were obtained underdifferent light wavelengths and gases circumstance, respectively. The experimentalresults verified the correctness of our previous theoretical analysis.
Keywords/Search Tags:Micro-nano fiber, Carbon Nanotubes, LB coating, gas sensing, mode fieldcharacteristics
PDF Full Text Request
Related items