| The THz region located between 0.1 and 10 THz has many superior features, Such as, itsenergy is very low . Many biological macromolecules have strong absorption and resonance in theTHz region. The signal to noise ratio in time-domain spectrum is high and so on. It has been widelyapplied in the astrophysics, materials science and information science. THz crystal resonator as akind of wavelength selection device has many advantages including small, simple production andhigh quality factor. It is broadly used in THz systems which consist of THz laser , filters, reflectors,cross-connectors and so on. Therefore the THz crystal resonator is important for the application inTHz technology.The characteristic of two-dimensional gradient THz photonic crystal resonant cavity is studiedin this paper. Firstly five kinds of two-dimensional gradient THz photonic crystal according to thebasis of square lattice photonic crystal are designed. The transmission spectra of five kinds oftwo-dimensional gradient THz photonic crystal are obtained by finite difference time domainmethod to study the impact of different structures on the transmission spectra. The transmissionspectra both in gradient THz photonic crystal and square lattice photonic crystal are analyzed andcompared. The simulation results show that gradient THz photonic crystal band gap is bigger thansquare lattice photonic crystal. On this basis, two-dimensional gradient THz photonic crystals withtwo kinds of point defects are respectively designed to construct cavity. By changing the size ofdefects, the changed situations in the resonant frequency, line width and Q value are obtained.Through comparing and analyzing, the gradient THz photonic crystal with narrower line width andhigher Q value are designed respectively under the circumstances of two types of point defects.Finally, according to the features of this THz cavity with gradient photonic crystal structure, itsapplications both in the filter and laser are discussed. |
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