| Infrared wave has excellent characteristics such as transient,coherence,broadband,low energy,making it has a wide range of applications in many fields such as astronomy,biology,materials,communications,military,and national defense.The development of infrared detectors is important to the infrared technology.In the detection of infrared bands,photon detectors,as a traditional choice,have the disadvantages of large volume and high temperature requirements,so it is necessary to develop and utilize thermal radiation detectors that do not have these disadvantages.Nowadays,with the development of scientific research,thermal radiation detectors have already been applied in commercial fields.But infrared detectors is still needed,which is more sensitive,fast-reacting,low-cost and easy to integrate.In recent years,carbon nanotubes(CNTs)have become one of the hotspots of scientific research for their excellent photoelectric properties.In this thesis,we based on the application of carbon nanotubes in infrared detection and used the finite element simulation software to carry out the following research work:1.Research of optical antenna integrated single-wall carbon nanotube filmFirst,we use the Drude model and effective medium theory to solve the dielectric constant of the single-walled carbon nanotube film and calculated the photoelectric characteristics of the detector composed of the film in the terahertz band based on the photothermoelectric effect.Then we integrate a bowtie antenna on this and calculated its absorption rate and polarization sensitivity.In these processes,single-walled carbon nanotubes film has been p-n doped and formed a p-n junction at the center,and the junction is aligned with the middle gap of the antenna.Due to the film is affected of antenna’s optical characteristics,we finally calculated that the polarization of the detector along the antenna axis and perpendicular to the antenna axis can reach 1753 at 1 THz and13000 at 0.5 THz.We can change the resonance frequency of the antenna by changing the size of the antenna.After changing the size(95μm、150μm、300μm),the peak polarization sensitivity of detector in the range of 0.5 to 1.5 THz is more than 700 at different resonance frequencies and 16 to 320 times higher than the case of without antenna integrated.In addition,the responsivity is 1 to 2 orders of magnitude higher than the case of without antenna integrated.2.Use the F-P cavity and change structure to improve the optical coupling efficiency of the bowtie antennaBased on integrated bowtie antenna of the single-wall carbon nanotube film detector,we add a metal plane under the base of the detector to form an F-P cavity and adjusted the load resistance of antenna to enhance the responsivity and polarization of the detector.First,we use the coupled-mode theory to explain the electric field enhancement at the middle gap of the antenna after adding the F-P cavity and the optimum thickness of the cavity is 13μm.After that,by changing the length of the extension bar at each tip of the two wings of the bowtie antenna,we can adjust the load resistance to further enhance the optical coupling effect of the antenna.From our calculations,after the enhanced optical coupling effect,the responsivity of the detector at 1 THz is increased by 19.9 times compared with the case of only the integrated antenna to 1500 V/W,and polarization is also increased to 33400.By changing the size of the antenna(95μm、171μm、200μm、379μm),at 0.5～1.5 THz,we find that the peak responsivity is increased by 8.1 to 19.9times compared with the case of only the integrated antenna,and polarization at the peak position is also increased by 2.7 to 22.3 times,and it reaches 3.04×10~5 at 0.5 THz. |
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