OPTICAL MODE TRANSFORMER, IN PARTICULAR FOR COUPLING AN OPTICAL FIBER AND A HIGH-INDEX CONTRAST WAVEGUIDE

摘要

A semiconductor-based optical mode transformer (100, 100, 100 ') is describedfor coupling an optical mode of anoptical fiber (3) with an optical mode of a waveguide (2a). The optical modetransformer comprises a first waveguide (la) extendingalong a first main longitudinal direction (Z) and including an end facet (9)being apt to be coupled to the optical fiber (3), saidfirst waveguide (1a) including a first core (1) and a first cladding (6,4)andhaving a first refractive index contrast (.DELTA.n1); and a secondwaveguide (2a) arranged with respect to said first waveguide so as to realizean evanescent optical coupling with said firstwaveguide (1a), the second waveguide (2a) comprising a second core (2) and asecond cladding (4,7) and having a second refractiveindex contrast (.DELTA.n2). In addition, the second core (2) comprises atapered region (13,13 ), in at least a portion of which saidevanescent coupling takes place. The first core (1) of the first waveguide(1a) and the second core (2) of the second waveguide(2a) are separated by a gap (g). The thickness (T2) of said second waveguide(2a) is comprised between 120 nm and 180 nm andthe second refractive index contrast ?n 2is greater than 40%, or the thickness(T2) of said second waveguide (2a) is comprised 100nm and 400 nm and the second refractive index contrast .DELTA.n2 is comprisedbetween 18% and 30%. The first refractive index contrastis smaller than the second refractive index contrast.