Abstract
Graphene integrated photonics provides several advantages over conventional Si photonics. Single layer graphene (SLG) enables fast, broadband, and energy-efficient electro-optic modulators, optical switches and photodetectors (GPDs), and is compatible with any optical waveguide. The last major barrier to SLG-based optical receivers lies in the current GPDs’ low responsivity when compared to conventional PDs. Here we overcome this by integrating a photo-thermoelectric GPD with a Si microring resonator. Under critical coupling, we achieve >90% light absorption in a ~6 μm SLG channel along a Si waveguide. Cavity-enhanced light-matter interactions cause carriers in SLG to reach ~400 K for an input power ~0.6 mW, resulting in a voltage responsivity ~90 V/W, with a receiver sensitivity enabling our GPDs to operate at a 10−9 bit-error rate, on par with mature semiconductor technology, but with a natural generation of a voltage, rather than a current, thus removing the need for transimpedance amplification, with a reduction of energy-per-bit, cost, and foot-print.
Highlights
Graphene integrated photonics provides several advantages over conventional Si photonics
The resulting trade-off between length and absorption has implications for GPDs that operate via the photo-thermoelectric effect (PTE)[43,44,45]: Due to slow (~ps46) heat dissipation to the lattice via phonon mediated cooling[46,47], photo-excitation leads to the formation of a hot-carrier distribution in SLG8,43,44
To increase the generated VPTE upon optical illumination according to Eq (1), encapsulation of the Single layer graphene (SLG) channel in hexagonal boron nitride (hBN) ensures a high (>104 cm2/Vs) μ55 for large (~200 μV/K) peak S29, according to Mott’s formula[43,44]: S
Summary
Graphene integrated photonics provides several advantages over conventional Si photonics. SLG’s optical absorption is ~2.3% under normal incidence[41], which limits the photoresponse in top-illuminated GPDs8 This can be increased in a WG configuration through the interaction with the evanescent field of the optical WG mode[42]. The resulting trade-off between length and absorption has implications for GPDs that operate via the photo-thermoelectric effect (PTE)[43,44,45]: Due to slow (~ps46) heat dissipation to the lattice via phonon mediated cooling[46,47], photo-excitation leads to the formation of a hot-carrier distribution in SLG8,43,44. In order to achieve a high (>mV) VPTE, it is better to absorb the incident electromagnetic energy over small (
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