Silicon Ribbon-Based Dual-Beam Optical Phased Array with Low Crosstalk and Large FoV

In this paper, a silicon ribbon (SR)-based microstructure is developed and added to a 32-channel optical phased array (OPA) to reduce the crosstalk between the antennas of grating waveguides. The spacing between the chirped grating antennas can be as close as 600 nm to effectively improve the field of view (FoV) of the OPA in the horizontal direction to 95 degrees. This SR-based approach substantially reduces the side lobe by 10 dB, effectively suppressing the noise and increasing the main lobe by 6 dB and considerably expanding the grating length with linear energy decay. The full width at the half maximum of the light spot reaches about 0.24 degrees. The antenna sites can simultaneously be scanned vertically by bi-directional inputs, effectively increasing the FoV to 30 degrees in the vertical direction.

Chirped Grating IR-Filter on a Waveguide for Sensing Applications

We present results for a specific filter design for silicon waveguides, which features a transmission wavelength and bandwidth well suited for carbon dioxide sensing. Simulations were performed using Comsol Multiphysics and the design was optimized for a central wavelength of 4.26 µm. Furthermore, we included real-world effects like the discrete resolution of the design grid as well as process-specific fabrication tolerances. The devised structures were based on a photonic waveguide concept, which was developed recently for evanescent-field-based sensing applications. Slab waveguides with gratings on top as well as strip waveguides with sidewall gratings were considered. The concept and design are discussed in detail in order to highlight the underlying ideas.