A polarization-insensitive graphene-assisted electro-optic modulator is proposed. The orthogonal T-shaped metal slot hybrid plasmonic waveguide allows the polarization-independent propagation of transverse electric field mode and complex mode. By the introduction of dual-layer graphene on the ridge waveguide, the polarization-insensitive modulation depths of the TE mode and complex mode are 0.511 dB/µm and 0.502 dB/µm, respectively. The 3 dB bandwidth of the modulator we have proposed is about 127 GHz at the waveguide length of 20 μm. The power consumption of 72 fJ/bit promised potential graphene electro-optic modulator applications for on-chip interconnected information transfer and processing.

In this work, we have proposed and designed a 1 × 1 optical switch based on the optical phase-change material, Ge₂Sb₂Se₄Te₁ (GSST), for GSST-assisted silicon racetrack microring. Its optical power can periodically be exchanged between the straight silicon waveguide and the GSST/Si hybrid racetrack waveguide due to the formed directional coupling structure. By changing GSST from the crystalline state to the amorphous state, the switch shifts from the ON state to the OFF state, and vice versa. With finite-difference time-domain method optimization, the proposed switch shows an extinction ratio of 18 dB at 1547.4 nm. The insert losses at the ON and OFF states are both less than 1 dB. The proposed switch unit has the potential to build an N × N switch matrix.

Mode division multiplexing (MDM) is a promising technology for the capacity enlargement of the optical transmission network. As a key element in the MDM system, the mode converter plays an important role in signal processing. In this work, a wideband E₀₀-E₁₀ silicon mode converter constructed by Y-branch and cascaded multimode interference coupler is demonstrated. The theoretical mode crosstalk is less than –29.2 dB within the wavelength range from 1540 nm to 1600 nm. By 180 nm standard CMOS fabrication, the tested mode conversion efficiency of 91.5% and the crosstalk of −10.3 dB can be obtained at 1575.9 nm. The 3 dB bandwidth is over 60 nm. The proposed E₀₀-E₁₀ silicon mode converter is applicable in mode multiplexing.

Micro-ring resonator (MRR) is a key element in in- tegrated optics. The mutual-coupling in dual-concentric MRR has great influence on the resonance output. In this work, high-Q silicon dual-concentric MRR and racetrack resonator have been investigated by the coupled mode theory. The theoretical model is built to explain and alleviate the phenomenon of resonance split- ting. CMOS fabrication is adopted for the preparation of dual- concentric MRR and racetrack resonators. The highest Q-factors of dual-concentric MRR and racetrack resonator are measured to be ∼9.00×10 ⁴ at 1530.783 nm and ∼7.32×10 ⁴ at 1536.596 nm, respectively. The notch depth improvement over 20 dB has been demonstrated on the 5-μm-radius double-ring structure. The experimental results prove that the asymmetry of resonance split- ting can be tuned by adjusting the distance between the inner- ring and outer-ring, as well as the waveguide width. The pro- posed work has potentials in the design and optimization of dual- concentric ring resonators.