Add/drop filters are key components of Wavelength Division Multiplexing (WDM) communication systems. Free spectral range(FSR) is a key parameter for Add/drop filters, the FSR should operate within the entire C-band (1530-1562nm).And flat-top drop-port response with a sharp rolloff is also import, Flatness of the passband, sharp roll-off from passband to stop band are necessary to minimize the pulse broadening and the packing efficiency of wavelength channels. In this paper, we proposed an asymmetric approach to design high-order microring filters, The aim is to achieve large extension ratios and adequate suppression of the spurious interstitial mode, meanwhile, flat-top and steep-side response in filter could be obtained by this approach. Our simulation results showed an extended FSR of 40nm, reducing the interstitial peak suppression from 5dB to 35dB and a boxlike filter response with sharpe factor(SF) of 0.68. And a quality-factor of 2961 and a 3-dB bandwidth of 0.52nm is achieved.
In this paper, we proposed a novel photodetector composed of cascaded microring resonators on silicon-on-insulator. In order to enhance the tolerance of signal wavelength drifting in optical communication, the photodetector was designed with a flat-top steep-edge response. In the photodetector, we used polarization insensitive cascaded silicon microring resonators as optical filter cavity, and used a silicon racetrack resonator bonded in p-i-n chip as optical detecting cavity. We used finite element (FE) mode solver, finite different time domain (FDTD), and transfer matrix method (TMM) to simulate the behavior of the polarization insensitive optical filter. With optimized parameters, the photodetector showed high quantum efficiency, narrow line width, and flat-top steep-edge.
A new type of subwavelength plasmonic waveguide based on a core-shell structure has been proposed. It is based on a semicylinder-shape dielectric-loaded plasmonic waveguide supporting the excitation of surface plasmon polaritons (SPPs). Simulation results reveal that the proposed waveguide exhibit a better trade-off in terms of mode localization and propagation length when compared to the traditional dielectric-loaded plasmonic waveguide. In addition, a ring resonator formed with the proposed waveguide shows a perfect performance with 1.8nm bandwidth and 23dB extinction ratio.