Analysis and design of grating couplers

Continuously apodized fiber-to-chip surface grating coupler with refractive index engineered subwavelength structure

“…In either case, efficient coupling of light from an optical fiber to (and from) the microphotonic chip is challenging because of the small size of the silicon waveguide core (∼250 nm × 450 nm). Surface grating couplers are a promising fiber-chip coupling solution [7,8]. They operate by laterally expanding the light propagating in the waveguide by means of an adiabatic taper, along with diffraction coupling it to (or from) an optical fiber positioned over the grating [see Fig.…”

A New Leaky-Wave Directional Coupler in Hybrid Dielectric-Waveguide Printed-Circuit Technology

“…In the optic range, several studies have been performed to conceive optic couplers using dielectric guides and prisms [6]. The most well-known leaky-wave coupler in the optic range is the so called "grating coupler" [7][8] shown in Fig.1-b. The periodic discontinuities inserted in the dielectric guide excite the m=-l radiating space-harmonic.…”

“…This harmonic is used as a radiating backward leaky-wave, which couples the energy from the input port to the coupled port, as shown in Fig.1-b. The grating must be designed so that all the energy radiated is absorbed by the receiving grating, minimizing the scattered energy (maximum coupling efficiency) [7,8]. In this paper, a new leaky-wave coupler is presented, together with the design procedure to obtain coupling under maximum efficiency conditions.…”

3D Beamforming Coupler for 2D Waveguides Using Dielectric Scatterer Array

“…f mn e jβ a R mn R mn (6) where A is an appropriate coefficient, M and N are the numbers of the scatterers in the x and y directions, f mn is a complex weight that represents scattering amplitude of the (m, n)-th scatterer, R mn is the distance from each scatterer to the observation point, and β a is the wavenumber of the radiated microwaves in the air. Considering the location-dependent amplitude decay and phase delay of the guided wave, f mn is modeled as follows…”