Study On Integrated Optoelectronic Devices Based On Graphene-silicon Waveguides

As an emerging two-dimensional material,graphene is attracting much attentions in the field of integrated optoelectronics,especially in CMOS-compatible silicon photonics,due to its excellent electro-optical properties.The modal effective refractive index in the graphene-silicon waveguide can be dynamically tuned at high speed,providing a promising approach for realizing tunable integrated optoelectronic devices and thus injecting new vitality to on-chip optical interconnects.In this thesis,several integrated optoelectronic devices using microring resonators or Y-junctions based on graphene-silicon waveguides are studied.Its contributions and innovations are given below:1.A bandwidth-tunable optical bandpass filter using cascaded graphene-silicon microring resonators is proposed.Triple series-coupled microring resonators based on graphene-silicon waveguides are used to construct the proposed device.By changing the chemical potential of graphene,the resonant wavelength of the triple series-coupled microring resonator based on graphene-silicon waveguides is shifted and then transmission spectra of four triple series-coupled microring resonators based on graphene-silicon waveguides are coherently combined to realize bandwidth-tunable optical bandpass filter.By optimizing structural parameters for the graphene-silicon waveguide and filter,the designed device can achieve a dynamic bandwidth tuning range of 2.70nm-6.30 nm with an in-band ripple of less than 1d B.When the bandwidth is tuned to the maximum,the designed device has an extinction ratio of greater than 92.35 d B,an insertion loss of 1.41 d B,and a shape factor of 0.71.2.A two-mode optical switch using a graphene-silicon Y-junction is proposed.The proposed device adopts a symmetrical Y-junction in which the two arms are composed of graphene-silicon waveguides.When graphene's chemical potential is tuned by the applied voltage signal,the modal effective refractive index in the output arm is changed,and thus the working state of the proposed device can be switched at high speed.The designed two-mode optical switch supports input TE0 and TE1 modes and the input modes can be flexibly separated,converted and routed.By optimizing structural parameters for the graphene-silicon waveguide and Y-junction,the 3-d B bandwidth of the designed device is about 47.94 GHz,the energy consumption is only 2.90 p J/bit,the area is about 65×1.7?m2,and the crosstalk is less than-12.10 d B within a bandwidth from 1505 nm to 1600 nm.3.A graphene-silicon photodetector using a microring resonator is proposed.An all-pass microring resonator is used for constructing the photodetector to enhance the interaction of graphene and light and improve the responsivity.To obtain structural parameters for the silicon microring resonator satisfying the critical coupling condition,silicon microring resonators are first designed,optimized,fabricated,and characterized.Graphene is transferred onto the surface of the silicon microring resonator satisfying the critical coupling condition and then patterned.Electrodes are deposited to form the graphene-silicon photodetector using a microring resonator.By analyzing the measured volt-ampere characteristic curves of the fabricated photodetectors with different input optical power levels,the best responsivity R is 12.5?A/W.