Mode Converter and Multiplexer With a Subwavelength Phase Shifter for Extended Broadband Operation

Abstract

On-chip mode converters and multiplexers are fundamental components to scale the capacity of silicon optical interconnects by using different spatial modes of waveguides. Recently, we proposed a low loss and compact mode converter and multiplexer consisting of a subwavelength-engineered multimode interference coupler, tapered waveguides as phase shifter and a symmetric Y-junction. However, the narrow spectral response of the tapered phase shifter limited the device crosstalk performance. In this work, we demonstrate that the use of a subwavelength grating phase shifter with low phase-shift errors substantially reduces the crosstalk and expands the operational bandwidth. A complete multiplexer-demultiplexer link consisting of two devices in back-to-back configuration was fabricated in a 220-nm siliconon-insulator platform. Experimental measurements of the complete link show insertion loss below 2 dB and crosstalk less than -17 dB over a bandwidth of 245 nm (1427 -1672 nm).

Fully integrated and broadband Si-rich silicon nitride wavelength converter based on Bragg scattering intermodal four-wave mixing

“…In order to reduce the device crosstalk and expand the operational bandwidth, the use of subwavelength grating PSs could be considered. These structures have also shown greater robustness to fabrication errors compared to conventional devices, as already demonstrated in previous works [46,47].…”

Silicon photonic mode multiplexers based on subwavelength metamaterials and on-chip beamforming

“…Recently, we have reported on a new two-mode multiplexer based on subwavelength-metamaterial-engineered MMI and phase shifter that overcomes the intrinsic wavelength-dependent performance of conventional counterparts [27]. .…”

Spatial and Polarization Division Multiplexing Harnessing On‐Chip Optical Beam Forming

“…MDM has been demonstrated based on multimode interference (MMI) couplers, asymmetric Y-junctions and directional couplers (DCs), adiabatic tapers, pixelated-meta structures, and subwavelength metamaterials. [6][7][8][9][10][11][12][13] Similarly, multiple devices have been reported for PDM, including MMIs, Mach-Zehnder interferometers (MZIs), diverse types of DCs (i.e., symmetric, asymmetric, tapered, bent, and based on extreme skin-depth), photonic crystals, slot waveguides, and subwavelength and tilted nano-gratings. [14][15][16][17][18][19][20][21][22][23][24][25][26][27] Despite the great diversity of proposed solutions, crosstalk still remains as one of the main impairments in high-speed optical communications, especially in systems with a high-channel count.…”