Study On Magneto-optical Properties Of Graphene-Photonic Crystal Composite Structure

Graphene, as a new kind of two-dimensional materials, has attracted intensive attention due to its abundant potential applications in ultra-high speed electronic devices, flexible optoelectronic devices, nanomechanics, etc. In particular, optical transitions between Landau levels of graphene displays strong circularly anisotropy and the circularly anisotropy is very sensitive to magnetic field, which can have important applications in magneto-optical modulator. This dissertation mainly discussed the magneto-optical properties of graphene under the magnetic field and the modulation of magneto-optical effect by graphene-photonic crystal composite structure. The main results are as follows:(1) The magneto-optical properties of graphene-photonic crystal microcavity composite structure are studied by a transfer matrix method. The Faraday rotation of graphene can be enhanced over eight times by the microcavity. The influence of detuning, i.e., the difference of the frequency of the optical transitions between Landau levels of graphene and the eigenfrequency of the microcavity, is investigated. The Faraday rotation of graphene embedded in a microcavity is very sensitive to detuning. With an appropriate detuning, the absorption of graphene in a cavity can be suppressed, and the Q value of the cavity increases. Thus the Faraday rotation and transmission are both enhanced. The Faraday rotation spectrum also displays a strongly asymmetric line shape.(2) The magneto-optical properties of graphene-quasiperiodic photonic crystal composite structure are studied by using a transfer matrix method. Two kinds of quasiperiodic sequence photonic crystals, i.e., Thue-Morse sequence and Fibonacci sequence photonic crystals, are investigated. The photonic localization in the quasiperiodic photonic crystal is relatively weaker than that in the photonic crystal microcavity, thus the enhancement of Faraday magneto-optical effect of graphene is relatively weaker. In a certain frequency range, quasiperiodic photonic crystals such as Fibonacci sequence photonic crystal have several resonant modes, thus several Faraday rotation peaks will appear. Hence graphene-quasiperiodic photonic crystal composite structure is more suitable for dealing with multi-frequency signal, such as the wavelength division multiplexing magneto-optical device.