Abstract: The invention relates to a silica optical waveguide having a clad layer and a core formed from a silica material and a method of fabricating the same and provides a silica optical waveguide in which the position of a core can be easily recognized and a method of manufacturing the same. The waveguide has a lower clad layer formed from silicate glass on a silica substrate, a core formed from silicate glass on the lower clad layer, and an upper clad layer formed of silicate glass on the lower clad layer so as to embed the core. A difference of height is provided on a top surface of the upper clad layer such that a difference between reflections from the position of the core and from other positions can be recognized on the top surface of the upper clad layer.

Abstract: The present invention is to provide a spot-size transformer which can transform the beam spot-size in a waveguide separated by a groove and a waveguide-embedded optical circuit using the spot-size transformer. The spot-size transformer according to the present invention comprises a first optical waveguide having a first core and a first cladding covering substantially the whole surface of the first core, a second optical waveguide having a second core provided as an extension of the first cladding and a second cladding, a transition waveguide positioned between the first and second optical waveguides, the transition waveguide having a first core whose width of the extension becomes gradually narrower as it goes toward the second optical waveguide.

Abstract: The present invention is to provide a spot-size transformer which can transform the beam spot-size in a waveguide separated by a groove and a waveguide-embedded optical circuit using the spot-size transformer. The spot-size transformer according to the present invention comprises a first optical waveguide having a first core and a first cladding covering substantially the whole surface of the first core, a second optical waveguide having a second core provided as an extension of the first cladding and a second cladding, a transition waveguide positioned between the first and second optical waveguides, the transition waveguide having a first core whose width of the extension becomes gradually narrower as it goes toward the second optical waveguide.

Abstract: An optical waveguide comprises a silica substrate, a buffer layer formed on the silica substrate, cores formed on the buffer layer, and upper cladding layer formed on the buffer layer, covering the cores. The thermal expansion coefficients of the buffer layer and upper cladding layer are set to be substantially equal. As a result, the stresses in the cores are isotropic, effectively suppressing birefringence.

Abstract: An optical waveguide comprises a silica substrate, a buffer layer formed on the silica substrate, cores formed on the buffer layer, and upper cladding layer formed on the buffer layer, covering the cores. The thermal expansion coefficients of the buffer layer and upper cladding layer are set to be substantially equal. As a result, the stresses in the cores are isotropic, effectively suppressing birefringence.

Abstract: The present invention is to provide a spot-size transformer which can transform the beam spot-size in a waveguide separated by a groove and a waveguide-embedded optical circuit using the spot-size transformer. The spot-size transformer according to the present invention comprises a first optical waveguide having a first core and a first cladding covering substantially the whole surface of the first core, a second optical waveguide having a second core provided as an extension of the first cladding and a second cladding, a transition waveguide positioned between the first and second optical waveguides, the transition waveguide having a first core whose width of the extension becomes gradually narrower as it goes toward the second optical waveguide.

Abstract: An optical waveguide having low polarization dependence having a lower clad layer formed on a substrate, a core layer formed on the lower clad layer and an upper clad layer in which the core layer is buried. The core layer and the upper clad layer of the optical waveguide are made of a material comprising glass as a major component. The polarization dependence is lowered by optimizing the relationship between the coefficients of linear expansion softening temperatures of the optical waveguide layers.

Abstract: The invention relates to a silica optical waveguide having a clad layer and a core formed from a silica material and a method of fabricating the same and provides a silica optical waveguide in which the position of a core can be easily recognized and a method of manufacturing the same. The waveguide has a lower clad layer formed from silicate glass on a silica substrate, a core formed from silicate glass on the lower clad layer, and an upper clad layer formed of silicate glass on the lower clad layer so as to embed the core. A difference of height is provided on a top surface of the upper clad layer such that a difference between reflections from the position of the core and from other positions can be recognized on the top surface of the upper clad layer.

Abstract: An optical waveguide comprises a silica substrate, a buffer layer formed on the silica substrate, cores formed on the buffer layer, and upper cladding layer formed on the buffer layer, covering the cores. The thermal expansion coefficients of the buffer layer and upper cladding layer are set to be substantially equal. As a result, the stresses in the cores are isotropic, effectively suppressing birefringence.

Abstract: An optical waveguide is made of a glass based component, has low polarization dependence, and comprises a lower clad layer formed on a substrate, a core layer formed on the lower clad layer and an upper clad layer in which the core layer is buried, at least the core layer and the upper clad layer being made of a material comprising a glass as a major component, wherein if a coefficient of linear expansion of the core layer is denoted by ?core, a difference between a softening temperature Tcore of the core layer and a practically used temperature To by ?Tcore, a coefficient of linear expansion of the upper clad layer by ?clad, a difference between a softening temperature Tclad of the upper clad layer and the practically used temperature To by ?Tclad, and a coefficient of effective linear expansion of the substrate and of the lower clad layer by ?subs, then, a relationship, ? ? ? ? ? ? T core ? ? ? ? T clad = 2 ? ? core - ? subs - ? clad ? core - ? subs is satisfied.

Abstract: An optical waveguide is formed on a substrate 11 by the steps of (1) forming an lower clad layer 12, core layer 13, metal mask layer 14 and a photoresist layer 15, (2) patterning the photoresist layer 15 by using a photomask 16, (3) etching and patterning the metal mask layer 14 wider than a core of required width using the patterned photoresist layer 15, (4) removing the photoresist layer and the metal mask layer 14 after patterning the core layer 13 by using the patterned metal mask layer 14 to form core 13a, (5) forming an upper clad layer 17 on the lower clad layer 12 so as to bury the patterned core 13a.

Abstract: The present invention is to provide a spot-size transformer which can transform the beam spot-size in a waveguide separated by a groove and a waveguide-embedded optical circuit using the spot-size transformer.