A device comprising: a substrate comprising a waveguide material having a waveguide refractive index (RIWG); a first layer of oxide material on the substrate having a first refractive index (RI 1 ) lower than the waveguide refractive index (RIWG); an optical waveguide on the first layer of the oxide material, the optical waveguide comprising the waveguide material having the waveguide refractive index (RIWG); a second layer of the oxide material on the optical waveguide and the first layer of the oxide material, the second layer of the oxide material having a second refractive index (RI 2 ) higher than the first refractive index (RI 1 ) and less than the waveguide refractive index (RIWG), the first layer of the oxide material, the optical waveguide and the second layer of the oxide material forming an end face for light coupling, and the optical waveguide extending inwards from the end face and increasing in effective refractive index from the end face ; an index matching material on the second layer of the oxide material that encapsulates at least the second layer of the oxide material and the end face , a respective refractive index (RI IM ) of the index matching material being index matched to the first refractive index (RI 1 ); an optical fiber ; and an alignment structure extending outward from the end face , the alignment structure configured to about center a fiber end face of the optical fiber with the second layer of the oxide material at the end face , such that light from the optical fiber enters the second layer of the oxide material at the end face , or respective light from the second layer of the oxide material enters the optical fiber at the fiber end face . a substrate comprising a waveguide material having a waveguide refractive index (RIWG); a first layer of oxide material on the substrate having a first refractive index (RI 1 ) lower than the waveguide refractive index (RIWG); an optical waveguide on the first layer of the oxide material, the optical waveguide comprising the waveguide material having the waveguide refractive index (RIWG); a second layer of the oxide material on the optical waveguide and the first layer of the oxide material, the second layer of the oxide material having a second refractive index (RI 2 ) higher than the first refractive index (RI 1 ) and less than the waveguide refractive index (RIWG), the first layer of the oxide material, the optical waveguide and the second layer of the oxide material forming an end face for light coupling, and the optical waveguide extending inwards from the end face and increasing in effective refractive index from the end face ; an index matching material on the second layer of the oxide material that encapsulates at least the second layer of the oxide material and the end face , a respective refractive index (RI IM ) of the index matching material being index matched to the first refractive index (RI 1 ); an optical fiber ; and an alignment structure extending outward from the end face , the alignment structure configured to about center a fiber end face of the optical fiber with the second layer of the oxide material at the end face , such that light from the optical fiber enters the second layer of the oxide material at the end face , or respective light from the second layer of the oxide material enters the optical fiber at the fiber end face . <EOS>