A waveguide coupled surface plasmon sensor for detection of liquid with high refractive index (RI) is designed based on polymer materials. The effects of variation of the thickness of the Au film, polymethyl methacrylate (PMMA) buffer, and waveguide layer on the sensing performance of the waveguide are comprehensively investigated by using the finite difference method. Numerical simulations show that a thinner gold film gives rise to a more sensitive structure, while the variation of the thickness of the PMMA buffer and waveguide layer has a little effect on the sensitivity. For liquid with high RI, the sensitivity of the sensor increases significantly. When RI of liquid to be measured increases from 1.45 to 1.52, the sensitivity is as high as 4518.14nm/RIU, and a high figure of merit of 114.07 is obtained. The waveguide coupled surface plasmon RI sensor shows potential applications in the fields of environment, industry, and agriculture sensing with the merits of compact size, low cost, and high integration density.

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.

A high-resolution and wide-range pressure sensor based on π phase-shifted fiber Bragg grating (π-FBG) encapsulated with metal thin-walled cylinder is reported. The sensor has been tested with a wavelength-sweeping distributed feedback laser, photodetector and a H¹³C¹⁴N gas cell. To perceive temperature and pressure synchronously, a pair of π-FBGs are glued on the outer wall of the thin-walled cylinder along the circumferential direction with different angles. The interference of temperature is effectively corrected by a high-precision calibration algorithm. The reported sensor has a sensitivity of 4.42 pm/MPa, a resolution of 0.036% full scale (F.S.), and a repeatability error of 0.045% F.S. in the range of 0-110 MPa that corresponds to an ocean depth resolution of 5 m and a measurement range of eleven thousand meters to cover the deepest trench of the Ocean. The sensor features simplicity, good repeatability, and practicability.

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.