In this paper, a simultaneous three-mode silicon (de)multiplexer using a trident coupler and a 3 × 3 multimode interference (MMI) is presented. The fundamental (TE 0 ), first-order (TE 1 ), and second-order (TE 2 ) modes at the input are successfully demultiplexed and converted to three uniform fundamental modes (TE 0 ) at the output ports. The device is designed and optimized by numerical simulation using three-dimensional beam propagation method together with effective index method. The three-mode (de)multiplexing is achieved over the whole Cband with small insertion loss (< 0.9 dB) and crosstalk (< −17 dB). The proposed device also features with a small footprint (5 μm×400 μm) and a large fabrication tolerance against chip-size variations while maintaining the desired optical performance.

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Multimode optical switch is a key component of mode division multiplexing in modern high-speed optical signal processing. In this paper, we introduce for the first time a novel 2 × 2 multimode switch design and demonstrate in the proof-of-concept. The device composes of four Y-multijunctions and 2 × 2 multimode interference coupler using silicon-on-insulator material with four controllable phase shifters. The shifters operate using thermo-optic effects utilizing Ti heaters enabling simultaneous switching of the optical signal between the output ports on four quasi-transverse electric modes with the electric power consumption is in order of 22.5 mW and the switching time is 5.4 µs. The multimode switch exhibits a low insertion loss and a low crosstalk below − 3 dB and − 19 dB, respectively, in 50 nm bandwidth in the third telecom window from 1525 to 1575 nm. With a compact footprint of 10 µm × 960 µm, this device exhibits a relatively large width tolerance of ± 20 nm and a height tolerance of ± 10 nm. Furthermore, the conceptual principle of the proposed multimode switch can be reconfigurable and scalable in multifunctional on-chip mode-division multiplexing optical interconnects.

In this paper, we present a proposal for compact photonic wavelength filtering and 3-dB wavelength splitting device based on nanoplasmonic metal-insulator-metal structure. The working performance of the device has been accurately simulated using the temporal coupled-mode theory. We use a numerical simulation method of eigenmode expansion propagation for the overall design process. We show that the transmission efficiency of the drop filter can be significantly enhanced by applying specifically optimization of nanostub waveguide. The proposed structure has potential applications in highly efficient ultracompact integration circuits as well as in optical communication systems at nanoscale.