Wideband integrated high-speed graphene-silicon slot-waveguide electro-absorption modulator at 2 μm and 1.5 μm wavebands

Abstract

The 2-μm waveband, emerging as a highly promising candidate for optical communication, offers an extended wavelength window for high-speed optical transmission. Despite its potential, the development of integrated electro-optic (E/O) modulators operating at this wavelength range has been limited. Such E/O modulators are crucial for high-speed optical communication systems at the 2-μm waveband. In this work, we propose and experimentally demonstrate high-performance E/O absorption modulators based on a graphene-silicon slot waveguide. Our approach enables wideband, high-speed, efficient, robust and compact modulators at both 2-μm and 1.5-μm wavebands. This work represents a significant advancement towards the realization of high-speed integrated E/O modulators for optical communication systems operating at the 2-μm wavelength range.

Figures (5)

• Figure 1: Device concept. (a-c) Schematic and cross section of the graphene-silicon slot-waveguide E/O absorption modulator. (d) Optical microscope image of the graphene-silicon slot waveguide E/O absorption modulator. (e) SEM image of the graphene-silicon slot waveguide E/O absorption modulator.
• Figure 2: Double-layer-graphene slot-waveguide E/O modulator optimization. (a) Calculated and normalized absorption coefficient change $\Delta a$ versus the slot waveguide dimension. (b) Calculated normalized extinction ratio, bandwidth, insertion loss and modulation efficiency-bandwidth product of the slot waveguide modulator versus dielectric layer thickness. The highest modulation efficiency-bandwidth product was obtained at the dielectric layer thickness of 50 nm. (c) Calculated normalized extinction ratio, bandwidth, insertion loss and modulation efficiency-bandwidth product of the slot waveguide modulator versus double layer graphene overlap width. (d) Calculated normalized metgal absorption loss, modulation bandwidth and modulation efficiency-bandwidth product of the slot waveguide modulator versus electrode to waveguide distance. (e) Calculated eigenmode of the slot waveguide structure. (f) RC circuit model of the slot waveguide modulator.
• Figure 3: Characterization of the double-layer-graphene slot-waveguide modulator at 2µ m wavelength bands. (a) Optical transmission of the 2µ m waveband graphene modulator with different graphene length. (b) Optical transmission of the 2µ m waveband grating couplers. (c, d) Measured absorption coefficient of the graphene silicon slot waveguide modulator at 2µ m waveband. (e) Measured electro-optic S$_{21}$ frequency response of the modulator at 2µ m wavelength bands. The bandwidth of the modulator is beyond 22 GHz. (e). Measured eye diagram of the modulator at 2µ m wavelength bands at 25 Gbit/s and 20 Gbit/s.
• Figure 4: (a) Optical transmission of the 1.5µ m waveband grating couplers. (b) Measured absorption coefficient of the graphene silicon slot waveguide modulator at 1.5µ m waveband. (c) Measured electro-optic S$_{21}$ frequency response of the modulator at 1.5µ m wavelength bands. The bandwidth of the modulator is beyond 70 GHz. (e). Measured eye diagram of the modulator at 1.5µ m wavelength bands at 40 Gbit/s and 50 Gbit/s.
• Figure 5: Comparison of state-of-the-art E/O modulators at 2-µ m waveband.