PROCEEDINGS ARTICLE | August 14, 2018
Proc. SPIE. 10830, 13th Conference on Integrated Optics: Sensors, Sensing Structures, and Methods
KEYWORDS: Diffraction, Refractive index, Waveguides, Wave propagation, Integrated optics, Wave sensors, Planar waveguides, Waveguide modes, Evanescent wave coupling, Diffraction gratings
The structure composed of a single mode silica-titania slab waveguide on a BK7 glass substrates and a grating coupler embossed at the interface of slab waveguide to ambient is studied. Reported studies are focused on optimization of thickness of the slab waveguide, length of grating period and coupling angle, aiming at maximization of coupling angle homogeneous sensitivity, which is a product of effective index coupling angle sensitivity and slab waveguide homogeneous sensitivity. If effective index coupling angle sensitivity is varying with grating period then it has a local minimum. At this minimum coupling angle homogeneous sensitivity depends only on slab waveguide homogeneous sensitivity and a refractive index of medium where coupling angle is measured. Effective index coupling angle sensitivity is monotonous if is varying with waveguide film thickness. Monotonicity sign depends on grating period. Coupling angle homogeneous sensitivity considered a function of waveguide film thickness may have local maximum. However, depending on grating period, it can also be strictly increasing or decreasing function of waveguide film thickness, depending on a diffraction order, in which case it becomes very high. However in this case, coupling angle is quickly increasing and reaches π/2.
