OPTICAL GRATING COUPLING STRUCTURE

摘要

The invention relates to a grating coupler comprising: —an optical substrate arranged to transfer a light beam, and—a diffraction grating arranged on, or imbedded in, the surface of said optical substrate, said diffraction grating comprising diffraction grating elements comprising each a coating arranged asymmetrically on said diffraction grating elements. The grating coupler is further arranged to satisfy the condition: (n1×sin(IαI)+η2)/λ×P>1, wherein n1 is the refractive index of the optical medium to the incident light side of the diffraction grating elements, n2 is the refractive index of the optical medium to the diffracted light side of the diffraction grating elements, lal the absolute value of the incident angle of the light beam incident on the grating coupler λ is the vacuum wavelength of the diffracted light, and P is the period of the diffraction grating elements.

主权项

1. A grating coupler comprising:
an optical substrate arranged to transfer a light beam, and a diffraction grating arranged on, or imbedded in, the surface of said optical substrate, said diffraction grating comprising diffraction grating elements arranged substantially in the plane (A) of said diffraction grating, said diffraction grating elements defining for each cross section thereof, a normal (B) to said plane (A), said normal (B) separating said cross section into two substantially symmetrical portions, and said normal (B) further dividing said diffraction grating elements in a first side (FS) and a second side (SS), said first side (FS) being situated substantially in the proceeding direction of the propagating order of the diffracted light beam having the highest intensity, transferred from the diffraction grating, said second side (SS) being oriented opposite to said proceeding direction,
wherein each of said diffraction grating elements comprises at least one coating, said coating being arranged asymmetrically on said diffraction grating elements, and wherein a major portion of said coating is arranged either to said first side (FS), or to said second side (SS), a minor portion of said coating being arranged to said second side (SS) or to said first side (FS) respectively, the major portion and the minor portion being continuous and forming said coating, andwherein the grating coupler is further arranged to satisfy the condition:
(n1×sin(|α|)+n2)/λ×P≧1,whereinn1 is the refractive index of the optical medium to the incident light side of the diffraction grating elements,n2 is the refractive index of the optical medium to the diffracted light side of the diffraction grating elements,|α| the absolute value of the incident angle of the light beam incident on the grating coupler,λ is the wavelength of the diffracted light, andP is the period of the diffraction grating elements,and wherein said grating coupler has an efficiency substantially higher than 50% into either the first positive diffraction order or the first negative diffraction order.