Recently, semiconductor nanowires (SCNWs) have received much attention due to their crucial role in physiochemical science and their high prospect for essential applications in advanced devices such as solar cells, light-emitting-diodes, transistors and bio/chemical sensors. Vertically-aligned silicon nanowires (SiNWs) platform is considered as a strong candidate for advanced devices because of the high volume-to-surface area ratio as well as the high aspect ratio originating from the vertical structure. The CMOS compatibility of such a platform allows for cheap commercial manufacturing of nanophotonic integrated circuit. Nanowire diameter is usually on the order of several nanometers and is comparable to the Debye length and this often results in much larger sensitivity than their thin film. In this work, we design a vertically-aligned SiNW gas sensor optimized to detect carbon monoxide (CO) gas at the midinfrared (MIR) range. SiNWs of diameters of only 200 nanometers are grown on Si wafers. According to Liao et al, thin nanorods have a significantly better sensing performance than thick nanorods in the detection of C<sub>2</sub>H<sub>5</sub>OH and H<sub>2</sub>S (100 ppm) in air. In addition, (MIR) gas sensing is very useful and user friendly as the gases are directly detected when they flow through the active sensing region of the sensor with no required human interaction with the dangerous gases. Finite difference time domain (FDTD) simulations are performed to verify the results and a comparison between the FDTD results and the experimental ones are held.
In this work, we present an electro-optical modulator based on electromagnetically induced transparency (EIT). Our modulator employs a conductor-gap-silicon (CGS) microring resonator on each side of the input waveguide in a pushpull configuration utilizing an embedded electro-optical polymer (EOP). CGS waveguides support hybrid plasmonic modes offering a sound trade-off between mode confinement and propagation loss. The modulator is designed and analyzed using 3D finite difference time domain (FDTD) simulations. To have a high quality resonator, the rings are designed to have moderate waveguide propagation losses and a sub-micron radius of R = 805 nm. With an exact capacitance of just 1.06 fF per single microring resonator and applied voltage of 2 V, the exact energy consumption is estimated to be 4.24 fJ/bit. To the best of our knowledge, this figure represents 40% less power consumption in comparison with different modulators structures. The ultra-small capacitance of the proposed modulator and the instantaneous response of the used polymer make our design suitable for high bit rate applications. At the wavelength of -1550 nm-, the insertion loss is 0.34 dB and the extinction ratio is 10.23 dB.