| Base on the electric birefringence effect of nematic liquid crystal, its refractive index is tuned when theliquid crystal director is manipulated by changing the direction of the external electric field. Introducingnematic liquid crystal into disorder photonic crystal, it is easy to tune the band gap and localized mode bymanipulate the direction of the external field. This dissertation numerically calculates the localized mode andits photoluminescence characteristics of electrical tunable disorder liquid crystal photonic crystal in both onedimension and two dimensions.Firstly, the localized mode and its photoluminescence characteristics of electrical tunable disorder onedimensional photonic crystal with a nematic liquid crystal defect layer (NLC-DLPC) are calculatednumerically by TMM. After setting up the model and introducing ZnO gain phenomenological model, theresults are obtained as follow: the wavelength of the NLC-DLPC’s defect mode gets smaller as the increaseof the angle θ between the direction of the vertical incident light and the direction of the electric field; thelocalized phenomenon can be found in the light distributions of the defect modes, The localized phenomenonoccurs not in the midst layer but in the layers next to the defect layer, that is, the defect mode is the localizedmode; The defect mode whose wavelength is larger has a smaller Photoluminescence pump threshold. Therelative light intensity gets stronger firstly and turns weaker as the gain coefficient increase; there is a largerquality factor in these modes with smaller pump power.Secondly, the localized mode and its photoluminescence characteristics of electrical tunable disorderone dimensional nematic liquid crystal photonic crystal with a defect layer (1D1DL-NLCPC) are studiednumerically. We have proposed a tunable1D1DL-NLCPC laser, which has a defect layer and is filled withLC whose effective diffraction index can be manipulated by the direction of the external electric field. Theband gap of the1D1DL-NLCPC gets wide as θ increases, while the wavelengths of both band edges get short.As θ increases, the wavelength of the defect mode of1D1DL-NLCPC with a defect layer gets short, and itsrange matches with the20nm gain wavelengths of ZnO, which is one to two orders of magnitude larger thanalready published values for electrical tuning. The narrow half-width at half maximum of the defect mode ofthe1D1DL-NLCPC with a defect layer has been found as less than0.2nm. The defect mode is also thelocalized mode and light is not localized in the defect layer but nearby it. In a low pump rate, that is, a lowpump power, there will be a high relative light intensity. With these characteristics, the LC-filled1D1DL-NLCPC laser can be tuned in a20nm range, and offer a narrow laser with a low pump power.Lastly, introducing the finite difference time domain (FDTD) method and perfect match layer (PML)absorbing boundary condition, the electo-tunable localized modes in two dimensional nematic-liquid-crystalphotonic crystal with a point defect (1PD2D-NLCPC) are investigated by numerically simulation. Nematicliquid crystal5CB can be considered as a kind of uniaxial material, and its refractive index is easy to tune by manipulating the direction of the external electrical field when the electrical field intensity is large enough.The numerical simulations show as follow: as the direction of the external electrical field varies, the band gapin the1PD2D-LCPC changes respectively, that is, some wavelengths in the band gap become that outside theband gap, while some wavelengths outside the band gap become that in the band gap; When the wavelengthin the band gap is the wavelength of the sine source wave, the most of optical field energy is localized in thepoint defect; Therefore manipulating the direction of the external electrical field causes the change of thelocalized mode as well. |
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