No abstract

A fully electrically tunable microwave photonic filter is realized by the implementation of delay lines based on frequency-time conversion. The frequency response and free spectral range (FSR) of the filter can be engineered by a simple electrical tuning of the delay lines. The method has the capability of being integrated on a silicon photonic platform. In the experiment, a 2-tap tunable microwave photonic filter with a 3-dB bandwidth of 2.55 GHz, a FSR of 4.016 GHz, a FSR maximum tuning range from -354 MHz to 354 MHz and a full FSR translation range is achieved.

A novel microstrip lowpass filter (LPF) with good specifications such as wide stopband and sharp roll-off is reported. The filter structure consists of split ring resonator loaded by folded polygene patches. The proposed filter with −3 dB cutoff frequency at 1.57 GHz has been designed, fabricated and measured. The LPF has a wide stopband from 1.67 to 14 GHz with a rejection level greater than −20 dB, sharp roll-off rate equal to 170 dB/GHz and low insertion loss lower than 0.13 dB in 94% of the passband. Finally, a high figure of merit of 51,178 is obtained.

Recently, an approximate boundary condition [Opt. Lett. 38, 3009 (2013)] was proposed for fast analysis of onedimensional periodic arrays of graphene ribbons by using the Fourier modal method (FMM). Correct factorization rules are applicable to this approximate boundary condition where graphene is modeled as surface conductivity. We extend this approach to obtain the optical properties of two-dimensional periodic arrays of graphene. In this work, optical absorption of graphene squares in a checkerboard pattern and graphene nanodisks in a hexagonal lattice are calculated by the proposed formalism. The achieved results are compared with the conventional FMM, in which graphene is modeled as a finite thickness dielectric layer. We show that for the same truncation order, computation time can be reduced to one-ninth by the proposed formulation in comparison with the conventional FMM. Furthermore, the convergence rate is increased. Therefore, thanks to the improved convergence rate and reduced computational cost for a given truncation order, the computational time is saved more than 100 times for relative error of less than 1%. This is crucially important in analyzing two-dimensional periodic structures of graphene by the FMM.