Optical waveguide mounting substrate and optical communication device
An optical waveguide mounting substrate includes a wiring substrate, and an optical waveguide mounted on the wiring substrate with an adhesive layer being interposed therebetween. The optical waveguide includes a first cladding layer, a core layer formed on a surface of the first cladding layer facing toward the wiring substrate, and a second cladding layer formed on the surface of the first cladding layer facing toward the wiring substrate so as to cover a periphery of the core layer. An opening is opened on the second cladding layer-side, penetrating the second cladding layer and the core layer, and closed on the first cladding layer-side, and a metal film is provided on an end face of the core layer in the opening. The second cladding layer faces the wiring substrate via the adhesive layer. A part of the adhesive layer is filled in the opening.
1. An optical waveguide mounting substrate comprising:
a wiring substrate; and
an optical waveguide mounted on the wiring substrate with an adhesive layer being interposed therebetween,
wherein the optical waveguide comprises:
a first cladding layer,
a core layer formed on a surface of the first cladding layer facing toward the wiring substrate, and
a second cladding layer formed on the surface of the first cladding layer facing toward the wiring substrate so as to cover a periphery of the core layer,
wherein an opening is opened on the second cladding layer-side, penetrating the second cladding layer and the core layer, and entirely closed on the first cladding layer-side by the first cladding layer, and a metal film is provided on an end face of the core layer in the opening,
wherein the second cladding layer faces the wiring substrate via the adhesive layer,
wherein a part of the adhesive layer is filled in the opening,
wherein the opening has a first inclined surface comprising the end face of the core layer and ranging from an opened side to a closed side, and a second inclined surface opposed to the first inclined surface and ranging from the opened side to the closed side,
wherein an angle θ 1 between a surface of the second cladding layer facing toward the wiring substrate and the first inclined surface, an angle θ 2 between the surface of the second cladding layer facing toward the wiring substrate and the second inclined surface, a thickness T 1 of the first cladding layer, a thickness T 2 of the core layer, a thickness T 3 of the second cladding layer closer to the wiring substrate than the core layer, and a width W of the opening on the opened side satisfy: a relation of T 2 +T 3 <W×tan θ 1 ; a relation of W×tan θ 1 <T 1 +T 2 +T 3 is satisfied; and an absolute value of a difference between the angle θ 1 and the angle θ 2 is equal to or less than 40°.
2. The optical waveguide mounting substrate according to claim 1 , wherein the angle θ 1 is 45°±5°.
3. The optical waveguide mounting substrate according to claim 1 , wherein a part on which the metal film is formed in the opening is within a range of the first inclined surface overlapping an area at an end of the opened side of the opening, as seen from above.
4. The optical waveguide mounting substrate according to claim 1 , wherein the first cladding layer, the core layer and the second cladding layer are formed of polymer.
5. An optical communication device comprising:
the optical waveguide mounting substrate according to claim 1 ; and
at least one of a light-emitting element and a light-receiving element, the light-emitting element configured to emit light toward the optical waveguide, the light-receiving element configured to receive light emitted from the optical waveguide.