Study Defect Modes Of Electrical-tunable Characteristics Based On One-dimensional Liquid Crystal Photonic Crystal

The one-dimensional photonic crystal is filled with the liquid crystal.Because of the liquidcrystal birefringence which is also more sensitive to the electric field and temperature changes,theaim to select frequency filtering can be achieved by regulating the effective refractive index of theliquid crystal by an applied electric field and temperature. Compared to other filters, the photoniccrystal filter has advantages in terms of the tuning range, and the ability to inhibit the otherchannel.When electric intensity is greater than threshold, liquid crystal can be looked as a uniaxialmedium, its refractive index can change by the direction of the electric field. We bring a defectlayer in photonic crystal, then make use of transmission matrix to study the defect mode ofone-dimensional photonic crystal which is filled by different kinds of liquid crystal, such as E7，5CB and BL-009. When these liquid crystals are controlled by the electric field, adjustable volumeof the wavelength of defect mode is43nm，34.5nm and37.1nm respectively. As the angleθ,which is between perpendicular incident light and electric field direction, increases in range of0degree to90degree, the wavelength of defect mode drifts to the short wave. It is due to the changeand variation of the effective refractive index on nematic liquid crystal.The defect mode is researched in liquid crystal one-dimensional photonic crystal by usingtransfer matrix method. As the thickness of ZnO layer or the liquid crystal(LC) layer is a fixedvalue, and the angle between the vertical incident light and the electric field direction is0,30,60,and90degree, the relationship between the wavelength of a one-dimensional photonic crystaldefect modes and the thickness of LC layer (or thickness of the ZnO layer) is numericallyresearched. The result shows that when the thickness of ZnO layer is fixed as90.8nm, thecorresponding LC thickness range of LC layer is from139nm to158nm for the opticalcommunication window of850nm wavelength, and when thickness of LC layer is141.7nm, thethickness range is from88.7nm to102.3nm. As the wavelength of defect modes is850nm, thesmaller that the angle between the vertical incident light and the electric field direction is, thesmaller that the thickness of LC or ZnO is relatively. Transfer matrix method was used to study the filling liquid crystal with a defect layer ofdefect modes of one dimensional photonic crystal. When the electric field is greater than thethreshold, the liquid crystal can be seen as the uniaxial substrate, whose index of refraction can becontrolled by changing the direction of the external temperature. The values in the paper simulatethe change rule of the defect modes due to the different directions of the electric field andtemperature, analyzing the electric field and temperature on the one dimensional LCD photoniccrystals containing defect modes regulation characteristics. All these comes to the conclusion,comparison with the temperature, the electric field has a bigger range of tenability. At the sametime, the paper analyses the distribution of the electric field of light incident Angle andtemperature field of formant which comes to the result that middle layer of the optical fieldintensity is the largest.