The Research On Characteristics Of Terahertz Modulator Based On Compound Lattice Photonic Crystals

The THz region (0.1THz~10THz) located between far-infrared and millimeter wave has receivedconsiderable attention as the last gap in electromagnetic spectrum. The THz frequency offers greaterbandwidth than is available at microwave frequencies. It experience much less scattering losscaused by particulates than do optical wavelengths. The trend of applying it to the future wirelesscommunications to solve the problem of high-speed, ultra-broadband wireless access connection isinevitable. THz modulator is the key component in future terahertz wireless communicationsystems. Meanwhile, phtonic crystal, as a new kind of material, is widely used to fabricatemodulators, switches, filters and other functional devices in optical communication systems. Thecombination of THz technology and photonic crystal (PC) technology provides a new approach todesigne a novel THz wave modulator. Therefore, researching the THz photonic crystal modulatorhas a lot of significance for the development of THz technology.The mechanisms of modulating the on-off state of the THz waves by using PC are firstlydescribed in this paper, and then a novel terahertz modulator based on two-dimensional photoniccrystal of compound lattice is presented. This compound lattice PC has an advantage of a largebandgap over common PCs in future THz WDM. On basis of the compound lattice PC, two kinds ofoptical controlled THz modulator are designed by introducing optical controlled GaAs as a tunanblematerial, respectively based on a round point defect resonator and a square point defect resonator.The impact of the point defect on modulation performance is discussed. It's found that Q value ofthe cavity is proportional to the response time and it's better to choose cavities with low Q value.Through the simulation, the transmission spectrum of the two modulators is analyzed, and detailedperformance of the devices is discussed including extinction ratio, modulation rates, andsteady-state energy distribution of the mode field. Comparing the above two modulators, it's foundthat the modulator with a square point defect is much better performed. It has a extinction ratio of49dB, modulation rate up to 3.3Gbit/s, pump power of 0.4μJ cm2 and insertion loss of 0.3dB. Inthe end, based on the features of the THz wave modulator of compound lattice PC, its applicationsand prospects in future THz wireless communication systems are briefly discussed.