Proposal for an ultracompact tunable wavelength-division-multiplexing optical filter based on quasi-2D photonic crystals

Abstract

The concept of an ultracompact and narrowband optical communication filter based on a combination of 2D photonic and quasi-2D photonic crystals (Q-2-DPC) has been proposed. We utilized an array of 12-fold quasiphotonic crystals (PhC) as a defect part in a 2D PhC structure. We show that the designed filter has the ability to tune its central wavelengths (λ0) by some parameters such as the radius of the rods in the Q-2-DPC section. Investigation of its properties has been done numerically by using the finite difference time domain (FDTD) method. The proposed filter has a cross section equal to 135.64 µm2 and thus it is verified that this structure is very small and can be integrated easily into optical integrated circuits with nanophotonic technologies. Tuning of the central wavelength of the filter output channel is realized by deviating the radius of the Q-2-DPC and we can mention that the channel space of 0.9–1.5 nm and bandwidth of 0.6–2.6 nm is accomplished near the communication wavelength of 1550 nm. Also, in the desired structure, wavelength shifting is achieved by modifying the size of the specific holes in the 12-fold Q-2-DPC section. Finally, the simulation results show that the desired structure can be considered as a narrowband and tunable optical filter that is useful for WDM and DWDM communication applications.