Unitary mounting structure for semiconductor laser and optical fiber

• US 4,523,802 A
• Filed: 02/08/1982
• Issued: 06/18/1985
• Est. Priority Date: 02/19/1981
• Status: Expired due to Term

• Current Assignee: Kokusai Denshin Denwa Kabushiki Kaisha A Joint-Stock Company of Japan
• Original Assignee: Kokusai Densin Denwa Kabushiki Kaisha
• Inventors: Seki, Norio, Okada, Akira, Yamamoto, Shu, Sakaguchi, Haruo
• Primary Examiner(s): Sikes, William L.
• Assistant Examiner(s): Ullah, Akm E.
• Application Number:
  US06/347,061
• Time in Patent Office: 1,226 Days
• Field of Search: 350/96.20, 350/96.12, 350/96.17, 350/96.11, 156/293
• US Class Current: 385/91
• CPC Class Codes: G02B 6/4202 for coupling an active element with fibres without intermediate optical elements, e.g. fibres with plane ends, fibres with shaped ends, bundles
• CPC Class Codes: G02B 6/4236 Fixing or mounting methods of the aligned elements
• CPC Class Codes: G02B 6/4238 Soldering

Abstract

A mount arrangement of a semiconductor laser and an optical fiber as a unitary structure. A substrate has a submount disposed thereon mounting a semiconductor laser. The laser is fixed on the submount by a fusion-welding material. A fiber submount is disposed on the substrate in the vicinity of the semiconductor laser submount. An optical fiber is fixed to the fiber submount with its optical axis coaxial with the optical axis of the output light of the semiconductor laser. The fiber submount includes a material for fixing the optical fiber and has a melting point such that it will not affect the coaxial optical alignment of the semiconductor laser and the optical fiber and the fixing between the substrate, the laser submount and between the laser submount and semiconductor laser during fabrication. The thickness of the semiconductor laser submount and the fiber submount are selected in terms of the interrelation between the coefficients of linear thermal expansion of the materials forming them and the coefficient of linear thermal expansion of the optical fiber from the substrate, which are caused by temperature variations in a range including temperature variations during fabrication, are substantially equal to each other and displacement between the optical axes of the light output of the laser and optical fiber is avoided. The retention of the axes coaxial alignment minimizes reduction of the efficiency of the coupling of the optical fiber to the semiconductor laser.

Claims

1. A unitary structure for a semiconductor laser and an optical fiber, comprising:

a substrate;

a semiconductor laser submount, a mount for the submount disposed on the substrate;

a semiconductor laser fixed by a fusion-welding material on the semiconductor laser submount;

a fiber submount disposed on a substrate in the vicinity of the semiconductor laser mount and submount; and

an optical fiber fixed to the fixed submount disposed to be coupled coaxially with output light of the semiconductor laser;

the fiber submount including a fixing material stable over time having a melting point effective to not affect the fixedness stability between the substrate and the semiconductor laser submount and between the semiconductor laser submount and the semiconductor laser, the thicknesses of the semiconductor laser mount and submount and the fiber submount and fixing material being selected in terms of the interrelation between substantially common coefficients of linear thermal expansion of materials forming them and the coefficient of linear thermal expansion of the optical fiber so that expansion deviations of the semiconductor laser and the optical fiber from the substrate caused by temperature variations in a range including temperature variations in manufacturing steps are substantially equal to each other and effective to substantially reduce misalignment of the coaxial axes of the optical fiber and the output light of the semiconductor laser, and thereby minimize lowering of the coupling efficiency between the semiconductor laser and the optical fiber.

2. A unitary structure for a semiconductor laser and an optical fiber according to claim 1, wherein the fiber submount is composed of the fixing material alone.

3. A unitary structure for a semiconductor laser and an optical fiber according to claim 1, wherein the fiber submount is composed of a material having a coefficient of linear thermal expansion smaller than that of the fixing material.

4. A unitary structure for a semiconductor laser and an optical fiber according to claim 1, wherein the semiconductor laser submount is formed as a two-layer structure, and wherein one of the two layers contacts the substrate and is formed of a material having a coefficient of linear thermal expansion larger than that of the other layer.

5. A unitary structure comprising:

a substrate;

a semiconductor laser submount on the substrate;

means for stably fixing the semiconductor laser on the submount;

a fiber submount;

an optical device of material boundaries for transmitting a beam of electromagnetic energy output fixed on the fiber submount and disposed to be coupled coaxially with a beam of output light of the semiconductor laser, the fiber submount including a fixing material stable over time for fixing said optical device thereto and having a melting point effective to not affect the fixedness stability between the substrate and the semiconductor laser submount and between the semiconductor laser the thicknesses of the semiconductor laser submount, the fiber submount and the fixing material being selected in terms of the interrelation between the substantially common coefficients of linear thermal expansion of the materials forming them and the coefficient of linear thermal expansion of the optical device substantially the same as said coefficient so that thermal expansion deviations of the semiconductor laser and the optical device relative to the substrate caused by temperature variations in a range including temperature variations in fabrication steps are substantially equal to each other and effective to minimize misalignment of the coaxial axes of the optical device and of the output light of the semiconductor laser, and thereby minimize lowering of the coupling efficiency between the semiconductor laser and the optical device.

6. A unitary structure comprising;

a substrate;

a semiconductor laser submount;

a mount for said submount on the substrate;

a semiconductor laser fixed on said submount;

means for stably fixing the semiconductor laser on the submount;

a fiber submount disposed on the substrate in the vicinity of the semiconductor laser mount and submount;

an optical device of material boundaries for transmitting a beam of light output of the laser and fixed on the fiber submount disposed to be optically coupled coaxially with a beam of output light of the semiconductor laser, the fiber submount including a fixing material for fixing said optical device thereto and having a melting point such that it does not affect the fixedness stability between the substrate and the semiconductor laser submount and between the semiconductor laser submount and the semiconductor laser due to temperature variations, the thicknesses of the semiconductor laser submount and the fiber submount and fixing material being selected in terms of the interrelation between the coefficients of linear thermal expansion of materials forming them and the coefficient of linear thermal expansion of the optical device so that physical expansion deviations of the semiconductor laser and the optical device from the substrate caused by temperature variations in a range including temperature variations during fabrication are substantially equal to each other and effective to minimize misalignment of the coaxial axes of the optical device and of the output light of the semiconductor laser, and thereby minimize lowering of the coupling efficiency between the semiconductor laser and the optical device.

7. A unitary structure according to claim 6, in which the means for stably fixing the semiconductor laser comprises solder.