A compact optical switch based on a 2D photonic crystal (PhC) and a magneto-optical cavity is suggested and analyzed. The cavity is coupled to two parallel and misaligned PC waveguides and operates with dipole mode. When the cavity is nonmagnetized, the dipole mode excited by a signal in the input waveguide has a node in the output waveguide. Therefore, the input signal is reflected from the cavity. This corresponds to the state off of the switch. Normal to the plane of the PhC magnetization by a dc magnetic field produces a rotation of the dipole pattern in the cavity providing equal amplitudes of the electromagnetic fields in the input and the output waveguides. This corresponds to the state on with high transmission of the input signal. Numerical calculations show that at the 1.55 μm wavelength the device has the insertion loss $-0.42\mathrm{dB}$ in the on state, the isolation $-19\mathrm{dB}$ in the off state and the switch off and on ratio $P_{\text{on}}/P_{\text{off}}$ about 72. The frequency band at the level of $-15\mathrm{dB}$ of the resonance curve in off state is about 160 GHz.

We consider peculiarities of application of the temporal coupled-mode theory to the electromagnetic components with magnetic symmetry. The coupled-mode theory is widely used for analysis of reciprocal devices described by symmetrical scattering matrices and by unitary elements of symmetry, such as for example, a plane of symmetry. However, nonreciprocity and low symmetry of components described by antiunitary elements lead to a necessity of modification of the method. Using as an example a photonic crystal-based W-circulator described by an antiplane of symmetry, we show applicability of the method to the components with antiunitary elements. The circulator characteristics are calculated and compared with those obtained by a numerical method, demonstrating good agreement between the two methods.

We analyze possible mechanisms of switching in two-ports based on 2D photonic crystals (PhCs) with a magneto-optical resonator. The input and output waveguides can be side or front coupled with the resonator. The resonator operates with a dipole mode. In the switch with front coupling in the nonmagnetic state the standing dipole mode provides equal nonzero wave amplitudes in the input and output waveguides and therefore transmission of the signal from the input to output waveguides. This is the state on. The applied magnetic field normal to the plane of the PhC rotates the standing dipole mode by 90° setting the nodes in the input and output waveguides. This corresponds to the state off. On the contrary, in the switch with side coupling and nonmagnetized resonator, the standing dipole mode excited by a wave in the input waveguide has its node in the output waveguide. Therefore, the signal is reflected from the input port. This corresponds to the state off of the switch. Magnetization by a DC magnetic field produces a rotating dipole pattern in the cavity. Due to this rotating, the mode signal passes from the input port to the output one and this is the state on.