A high-performance silicon arrayed-waveguide grating (AWG) with 0.4-nm channel spacing for dense wavelength-division multiplexing systems is designed and realized successfully. The device design involves broadening the arrayed waveguides far beyond the single-mode regime, which minimizes random phase errors and propagation loss without requiring any additional fabrication steps. To further enhance performance, Euler bends have been incorporated into the arrayed waveguides to reduce the device’s physical footprint and suppress the excitation of higher modes. In addition, shallowly etched transition regions are introduced at the junctions between the free-propagation regions and the arrayed waveguides to minimize mode mismatch losses. As an example, a 32×32 AWG (de)multiplexer with a compact size of 900 μm×2200 μm is designed and demonstrated with a narrow channel spacing of 0.4 nm by utilizing 220-nm-thick silicon photonic waveguides. The measured excess loss for the central channel is ∼0.65 dB, the channel nonuniformity is around 2.5 dB, while the adjacent-channel crosstalk of the central output port is −21.4 dB. To the best of our knowledge, this AWG (de)multiplexer is the best one among silicon-based implementations currently available, offering both dense channel spacing and a large number of channels.
Dealing with the increase in data workloads and network complexity requires efficient selective manipulation of any channels in hybrid mode-/wavelength-division multiplexing (MDM/WDM) systems. A reconfigurable optical add-drop multiplexer (ROADM) using special modal field redistribution is proposed and demonstrated to enable the selective access of any mode-/wavelength-channels. With the assistance of the subwavelength grating structures, the launched modes are redistributed to be the supermodes localized at different regions of the multimode bus waveguide. Microring resonators are placed at the corresponding side of the bus waveguide to have specific evanescent coupling of the redistributed supermodes, so that any mode-/wavelength-channel can be added/dropped by thermally tuning the resonant wavelength. As an example, a ROADM for the case with three mode-channels is designed with low excess losses of <0.6, 0.7, and 1.3 dB as well as low cross talks of < − 26.3, −28.5, and −39.3 dB for the TE0, TE1, and TE2 modes, respectively, around the central wavelength of 1550 nm. The data transmission of 30 Gbps / channel is also demonstrated successfully. The present ROADM provides a promising route for data switching/routing in hybrid MDM/WDM systems.
Silicon photonics is recognized as one of the most promising platforms for on-chip optical interconnects. In order to further enhance the on-chip optical-interconnect link capacity, silicon photonic devices for advanced multiplexing technologies have been widely investigated, including wavelength-division-multiplexing (WDM), mode-divisionmultiplexing (MDM), as well as the hybrid multiplexing. This paper gives a review for our recent progresses in the development of silicon-based on-chip wavelength/mode-division-multiplexers.
Multimode silicon photonics have drawn tremendous attention because the introduction of higher-order modes greatly enhances the capacity of mode-division-multiplexing (MDM) data transmission systems as well as improves the flexibility of on-chip photonic device designs. As the cornerstone of multimode silicon photonics, plentiful multimodemanipulation photonic devices have been developed successfully. On the other hand, more and more emerging applications have been stimulated by higher-order modes introduced in multimode silicon photonics. This paper gives a review for our recent processes in the development of multimode silicon photonic devices. Keywords: mode, multiplexer, conversion, bend, filter, silicon, waveguide.
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