A novel electro-optic (EO) modulator based on graphene on silicon (GoS) dual-slot waveguide is proposed, utilizing the electro-absorption and electro-refraction effect of graphene. The optical mode in the waveguide can interact strongly with the upper graphene layer due to the enhancement of light intensity and poor mode confinement in the nanometer slot. The real part and imaginary part of effective modal index relate to the optical propagation phase and attenuation, respectively. Electro-absorption and electro-refraction modulators can be realized by reasonably tuning the chemical potential of graphene through an applied gate voltage. The geometric parameters of the GoS waveguide are well optimized. Simulation results show the phase shift can be linearly tuned from 0 to π by changing the gate voltage from 1 to 5.4 V for a 70 μm-long GoS dual-slot waveguide. When this waveguide is used as electro-absorption modulator, the modulation depth and insertion loss are 25 dB and 0.09 dB, respectively. The 3-dB bandwidth is estimated to be 79.6 GHz. The power consumption is ~0.94 pJ/bit and ~1.42 pJ/bit for the electro-refraction and electro-absorption modulation, respectively. The FoM (modulation depth/insertion loss) is as high as 273. This GoS dual-slot waveguide modulator with merits of footprint-compact, energy-efficient and CMOS compatible has potentials in on-chip optical interconnections.

Compact high-performance electro-optic (EO) modulators are key element for optical communications. An electro-absorption (EA) modulator is theoretically designed. Due to the introduction of graphene film over the silicon slot waveguide, the modulation efficiency is strongly improved. The effect of waveguide dimensions, dielectric insulator thickness, and carrier mobility on performances of proposed EO modulator have been comprehensively investigated. For the 120 $\mu$ m-long graphene-on-silicon waveguide modulator, the extinction ratio 28 dB and insertion loss 1.28 dB can be obtained at 1550 nm when drive voltage is 1.91 and 0.59 V, respectively. The 3-dB bandwidth of 117 GHz can be obtained at a small power consumption of 212 fJ/bit. The proposed modulator possesses a high figure-of-merit of 20.5. Its benefits of small size, power saving and process compatible promises possible applications in on-chip signal processing.

A polymer waveguide mode selecting switch (MSS) composed of two cascaded MMI couplers is demonstrated. The MSS can switch different data channels over E ₀₀ and E ₁₀ modes. Polymer waveguide dimensions are optimized with beam propagation method. The simulated results indicate that the worst insertion loss is 5.5 dB at 1550 nm and the switching powers for E ₁₀ mode between two different channels are 4.5 and 12.3 mW, respectively. The extinction ratio and crosstalk are less than 19.7 and -19.6 dB, respectively. The switching performances of fabricated MSS prove the functionality of proposed design, which promises its potentials in mode-division-multiplexing applications.

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.

Wideband and polarization-insensitive operation are key issues for electro-optic modulators. An electro-absorption modulator based on graphene-silicon nitride hybrid waveguide has been proposed. Geometric parameters are investigated through finite element method to enhance the interaction between the optical mode and the graphene. For a 200-μm-long hybrid waveguide, a modulation depth (MD) of 20 dB can be obtained when Femi level varies from 0.2 to 0.6 eV. The MD difference between the transversal electric polarization and transversal magnetic polarization (ΔMD) can be restrained to 4 × 10 ^-3 dB at 1550 nm. A low average ΔMD of 0.2 dB within the wavelength range from 1100 to 1645 nm can be obtained. The 3 dB-bandwidth of 53 GHz and a power consumption is 0.687 pJ/bit can be obtained. The proposed modulator has potentials for on-chip signal processing.

A bulk refractive index sensor based on a straight long-range surface plasmon polariton (LRSPP) waveguide is theoretically designed. The waveguide sensor consists of an Au stripe that is embedded in ultraviolet sensitive polymer SU-8. The geometric parameters are optimized by finite difference eigenmode method at the optical wavelength of 850 nm. The sensitivity of 196 dB/RIU/mm can be obtained with a 1.5 μm wide, 25 nm thick Au stripe waveguide. Straight LRSPP waveguides are fabricated by a double layer lift-off process. Its optical transmission is characterized to experimentally prove the feasibility of the proposed design. This sensor has potential for the realization of a portable, low-cost refractometer.