Cameron Horvath

All-plasmonic switching based on thermal nonlinearity in a polymer plasmonic microring resonator

We experimentally investigated thermal nonlinear effects in a hybrid Au/SiO(2)/SU-8 plasmonic microring resonator for nonlinear switching. Large ohmic loss in the metal layer gave rise to a high rate of light-to-heat conversion in the plasmonic waveguide, causing an intensity-dependent thermo-optic shift in the microring resonance. We obtained 30 times larger resonance shift in the plasmonic microring than in a similar SU-8 dielectric microring. Using an in-plane pump-and-probe configuration, we also demonstrated all-plasmonic nonlinear switching in the plasmonic microring with an on-off switching contrast of 4 dB over 50 mW input power.

Polymer Hybrid Plasmonic Waveguides and Microring Resonators

We report the design and fabrication of hybrid plasmonic waveguides based on the Au/SiO2/SU-8 material system. Monolithic integration of these devices with dielectric SU-8 waveguides on the same chip enabled efficient and broadband coupling between photonic and plasmonic devices to be achieved. Compact hybrid plasmonic microring resonators were also demonstrated with high intrinsic Q-factors close to 300.

Photothermal nonlinearity and optical bistability in a graphene–silicon waveguide resonator

We report observation of optical bistability due to enhanced thermal nonlinearity in a graphene-silicon waveguide resonator. Ohmic self-heating in the graphene layer results in a 2.7-fold increase in the nonlinear index over bare silicon waveguide.

Silicon microring refractometric sensor for atmospheric CO 2 gas monitoring

We report a silicon photonic refractometric CO(2) gas sensor operating at room temperature and capable of detecting CO(2) gas at atmospheric concentrations. The sensor uses a novel functional material layer based on a guanidine polymer derivative, which is shown to exhibit reversible refractive index change upon absorption and release of CO(2) gas molecules, and does not require the presence of humidity to operate. By functionalizing a silicon microring resonator with a thin layer of the polymer, we could detect CO(2) gas concentrations in the 0-500ppm range with a sensitivity of 6 × 10(-9) RIU/ppm and a detection limit of 20ppm. The microring transducer provides a potential integrated solution in the development of low-cost and compact CO(2) sensors that can be deployed as part of a sensor network for accurate environmental monitoring of greenhouse gases.

Fabrication and Characterization of Edge-Conformed Graphene-Silicon Waveguides

We report a simple and robust method for fabricating graphene-on-silicon waveguides on a silicon-on-insulator (SOI) chip. The waveguide consists of a silicon core covered by a graphene layer whose width exactly conforms with the width of the silicon core and whose length can be precisely controlled. Raman spectroscopy showed that the graphene layer retained its high quality after processing. Transmission measurements of fabricated graphene-on-silicon waveguides showed polarizationdependent propagation losses of 0.03 dB/μm for the transverseelectric (TE) mode and 0.07 dB/μm for the transverse-magnetic (TM) mode, in excellent agreement with theoretical simulations.

Thermal nonlinearity and optical bistability in a graphene-silicon waveguide resonator

We report observation of optical bistability due to enhanced thermal nonlinearity in a graphene-silicon waveguide resonator. Ohmic self-heating in the graphene layer results in a 2.7-fold increase in the nonlinear index over bare silicon waveguide.

Silicon photonic dual-gas sensor for H_2 and CO_2 detection

We report a silicon photonic dual-gas sensor based on a wavelength-multiplexed microring resonator array for simultaneous detection of H2 and CO2 gases. The sensor uses Pd as the sensing layer for H2 gas and a novel functional material based on the Polyhexamethylene Biguanide (PHMB) polymer for CO2 gas sensing. Gas sensing experiments showed that the PHMB-functionalized microring exhibited high sensitivity to CO2 gas and excellent selectivity against H2. However, the Pd-functionalized microring was found to exhibit sensitivity to both H2 and CO2 gases, rendering it ineffective for detecting H2 in a gas mixture containing CO2. We show that the dual-gas sensing scheme can allow for accurate measurement of H2 concentration in the presence of CO2 by accounting for the cross-sensitivity of Pd to the latter.