Abstract
The on-chip mode-division multiplexing (MDM) is an attractive technique to achieve high-capacity optical transmissions by using a single-wavelength carrier. In traditional schemes, multiple channels with a fundamental mode are modulated by parallel arranged electro-optic modulators and then converted to high-order modes. However, the method is usually limited by large device footprints and high energy consumption. In this work, we study a graphene-based waveguide-integrated multimode phase modulator to individually modulate TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> and TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> modes in a multimode waveguide device. To be specific, we designed a single layer of graphene narrow strips (GNSs) integrated on the surface of the multimode waveguide device to selectively introduce contrasting phase shifts to different modes. Based on the optimized waveguide structures, a Mach-Zehnder interferometer modulator with different GNS patterns on each arm is designed. Our study is promising to be used in the future high-density on-chip MDM systems for optical interconnects and optical networks.
Highlights
N OWADAYS, on-chip data communications require a data rate approaching 1 TB/s [1] passing through the network, which puts increasing demand for high-density, energy-efficient, and low-cost devices based on photonic integrated circuits (PICs) for optical networks and optical interconnects [2]–[4]
Various types of modeMUXer structures based on silicon (Si) PICs have been demonstrated, such as dual-mode multimode interference structures [10], adiabatic couplers [11], asymmetrical directional couplers [12], and topology optimized waveguides [13]
Layers of graphene narrow strips (GNSs) of different patterns separated by a thin insulator layer were integrated on the surface of the multimode waveguide
Summary
N OWADAYS, on-chip data communications require a data rate approaching 1 TB/s [1] passing through the network, which puts increasing demand for high-density, energy-efficient, and low-cost devices based on photonic integrated circuits (PICs) for optical networks and optical interconnects [2]–[4]. Waveguide-integrated graphene devices have been proposed for the applications of MDM, such as waveguide-integrated spatial mode filters [28] and multi-mode modulators [29], [30]. In such devices, layers of graphene narrow strips (GNSs) of different patterns separated by a thin insulator layer were integrated on the surface of the multimode waveguide. Compared with the current on-chip MDM schemes, our proposed device is easy for fabrication and has a compact footprint since it eliminates the need for mode converters and multiple modulators in parallel. Our design is promising for high-density on-chip MDM for future optical networks and computing applications
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