Abstract
In this paper, we propose a novel scheme to integrate an optical hybrid based on standing wave with graphene photodetector (GPD). Different from optical hybrids ba-sed on multimode interference (MMI) couplers, the proposed optical hybrid can be miniaturized by constructing a standing wave field in a silicon strip waveguide. The waveguide-integrated GPD with symmetric electrodes is adopted as an ultrafast self-differential photodetector (SDPD), instead of conventional balanced-photodetectors (BPDs) based on p-i-n photodiodes in a coherent receiver. By placing two sysmmetric interdigitated electrodes of the SDPD at nodes and antinodes of the standing wave, it is convenient to realize the integration of the proposed optical hybrid with the graphene-based SDPD, which can effectively reduce the complexity of a coherent receiver and meet the future demand for wide bandwidth. The finite-difference time-domain method was used to calculate optical absorption for demonstrating operation feasibility. Finally, device bandwidth and effective responsivity have been discussed. In theory, our scheme would provide a feasible way to realize a high-speed compact coherent receiver.
Highlights
Coherent detection, one of the most promising detection techniques, has been commonly used for high-speed data transfer due to its high sensitivity, high spectral efficiency, and the possibility of electronic compensation of signal impairments [1], [2]
The graphene photodetector (GPD) is used to allow for large bandwidth, and the operation of zero bias can lead to zero dark current
Our investigation concentrates on the responsivity, which is the major limitation for the applications of GPDs
Summary
One of the most promising detection techniques, has been commonly used for high-speed data transfer due to its high sensitivity, high spectral efficiency, and the possibility of electronic compensation of signal impairments [1], [2]. The development of integrated coherent receivers is an attractive step towards the miniaturization and high-speed application. Such integration of coherent receivers have been realized in InP photonic integrated circuits (PICs) [3]–[5], silicon PICs [6]–[9], and hybrid PICs [10]–[13]. They are usually designed as integrated MMI optical hybrids connected to PIN photodiodes pairs which are used for balanced detection.
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