Photonic-Crystal Demultiplexer With Improved Crosstalk by Second-Order Cavity Filtering

Abstract

Abstract-In this paper, we implement on a silicon-on-insulator (SoI) platform a photonic-crystal demultiplexer that operates on the principle of mini-stopbands of broader waveguides. Previous InP-based membrane versions showed modest crosstalk at 10 nm spacing. Here, we implement a second cavity in the form of a second parallel waveguide almost identical to the core one. Simulations employing three-modes coupled-mode theory and finite-difference time-domain help optimizing the coupling. The experimental realization with deep ultraviolet exposure and grating couplers is the first of this demux strategy on SoI. It successfully shows crosstalk in the 15-20 dB range on a very small footprint.

Performance Enhancement of Cavity Assisted Photonic Crystal De-Multiplexerin Slow Light Regime

“…Because of their weak optical confinement, these components are not of interest of the researchers, whereas more compact designs are possible based on photonic crystal technology [7,8]. Photonic crystal (PhC) based DEMUX designs are superior in this respect [7][8][9][10][11]. Various methods are proposed by researchers to provide the required frequency selectivity of the output channels.…”

Characterization of Integrated Planar Photonic Crystal Circuits Fabricated by a CMOS Foundry

“…), and the absolute transmission associated with each element. Numerous analyses of foundry-produced "full circuits" have been published [15], [31]- [35], and much work has been done on characterizing and optimizing various SOI-based grating coupler geometries [12], [13], [16], [36]- [48] and PPC microcavities [49], [50], but we believe this is the first full quantitative characterization of a CMOS-foundry-produced, PPC-based photonic circuit that integrates all three key building blocks using a single-etch process. While none of the individual components are "best in class", this work identifies i) methods for quantitatively analyzing a full circuit, ii) the sensitivity of various circuit component performance metrics to key wafer parameters (thicknesses of the silicon and oxide layers) that are often not well-specified by the supplier, iii) a post-processing method for shifting the tuning range of grating couplers, and iv) the impact of lens quality on free-space grating coupling efficiency.…”

Dual-frequency division de-multiplexer based on cascaded photonic crystal waveguides

“…Contemporary studies on WDM devices are targeted to achieve ultra compact, polarization insensitive devices with a low cross-talk ratio between the output channels [5,6]. Among the efforts in the literature that aim to create a de-multiplexing mechanism based on PC structures, PC waveguide directional couplers for de-multiplexing the desired wavelengths in the coupled parallel waveguides with different perturbations to create different resonance frequencies [7,8], PC based frequency selective micro cavities with different hole sizes to target different resonance frequencies [9], coarse wavelength de-multiplexers that have multimode waveguides in order to create a mini stop band from the interaction of the main waveguide mode with the higher order mode and to provide a difference in the spatial distributions of the modes that have different group velocities [10,11], classical bulk PCs by the usage of the self-imaging property [12], and classical bulk PCs that utilize the super-prism phenomenon for benefiting from the negative refraction to direct a set of targeted frequencies in the desired directions and thus creating a spatial and spectral de-multiplexing effect [13,14] should be mentioned. The method of cascading PC sections with unequal periodicities and waveguide widths is also used to achieve the extraction of different frequency bands from different output channels utilizing coupled cavity-waveguide combinations [15,16].…”