Grating coupler is one of the most basic integrated photonic components. Due to the excellent performance of compact non-mechanical beam steering, it has attracted a lot of research interest. Here we propose a new compound period grating coupler, which can couple the waveguide mode into two radiation modes with different angles by combining two grating structures with different periodicities. Therefore, the extra beam doubles the beam steering range. We numerically demonstrate this idea, and a steering range of 26.20 degree is observed within the wavelength tuning range of 1500 nm to 1600 nm. The compound period grating structure with DBRs (distributed Bragg reflectors) as the substrate has also been demonstrated numerically, and its energy leakage to the substrate is highly suppressed. Furthermore, investigation of fabrication tolerance shows the new structure can be fabricated with the current CMOS technology.
We have proposed and demonstrated numerically an ultrasmall and highly sensitive plasmonic hydrogen sensor based on an integrated microring resonator, with a footprint size as small as 4×4 μm2. With a palladium (Pd) or platinum (Pt) hydrogen-sensitive layer coated on the inner surface of the microring resonator and the excitation of surface plasmon modes at the interface from the microring resonator waveguide, the device is highly sensitive to low hydrogen concentration variation, and the sensitivity is at least one order of magnitude larger than that of the optical fiber-based hydrogen sensor. We have also investigated the tradeoff between the portion coverage of the Pd/Pt layer and the sensitivity, as well as the width of the hydrogen-sensitive layer. This ultrasmall plasmonic hydrogen sensor holds promise for the realization of a highly compact sensor with integration capability for applications in hydrogen fuel economy.