Patent ID: 8320721

Claim:
An optical mode transformer comprising: a first waveguide extending along a first main longitudinal direction and having a first end including an end facet configured to be coupled to an optical fiber, the first waveguide including a first core and a first cladding, and having a first refractive index contrast; a second waveguide comprising a second core and a second cladding, and having a second refractive index contrast, an end of the second waveguide being butt coupled to a second end of the first waveguide; and a third waveguide being arranged with respect to the second waveguide so as to realize an evanescent optical coupling with the second waveguide, the third waveguide comprising a third core and a third cladding, and having a third refractive index contrast, the third core including a tapered region in at least a portion of which the evanescent coupling takes placed; and wherein the first refractive index contrast is less than the second refractive index contrast, the second refractive index contrast is less than the third refractive index contrast, and the third refractive index contrast is not less than 18%.