Multiplex laser-light source and exposure system

• US 20040008744A1
• Filed: 07/10/2003
• Published: 01/15/2004
• Est. Priority Date: 07/10/2002
• Status: Active Grant

• Current Assignee: Adtec Engineering Company Limited (Ushio Incorporated)
• Original Assignee: Fuji Photo Film Co Limited (Fujifilm Holdings Corporation)
• Inventors: Nagano, Kazuhiko, Okazaki, Yoji, Kuramachi, Teruhiko
• Granted Patent: US 7,068,690 B2
• Time in Patent Office: Days
• US Class Current: 372/36
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01S 5/005 Optical components external to the laser cavity, specially adapted therefor, e.g. for homogenisation or merging of the beams or for manipulating laser pulses, e.g. pulse shaping H01S5/026, H01S5/18388 take precedence
• CPC Class Codes: H01S 5/02251 using optical fibres
• CPC Class Codes: H01S 5/02325 Mechanically integrated components on mount members or optical micro-benches
• CPC Class Codes: H01S 5/0234 Up-side down mountings, e.g. Flip-chip, epi-side down mountings or junction down mountings
• CPC Class Codes: H01S 5/0237 by soldering
• CPC Class Codes: H01S 5/02407 Active cooling, e.g. the laser temperature is controlled by a thermo-electric cooler or water cooling
• CPC Class Codes: H01S 5/02476 Heat spreaders, i.e. improving heat flow between laser chip and heat dissipating elements
• CPC Class Codes: H01S 5/32341 blue laser based on GaN or GaP
• CPC Class Codes: H01S 5/4012 Beam combining, e.g. by the use of fibres, gratings, polarisers, prisms
• CPC Class Codes: H01S 5/4031 Edge-emitting structures
• CPC Class Codes: H01S 5/405 Two-dimensional arrays

Abstract

In a laser-light source: submounts each being made of a material having a thermal expansion coefficient of 3.5 to 6.0×10⁻⁶/° C. and having a thickness of 200 to 400 micrometers are separately formed on a heat-dissipation block made of copper or copper alloy; a single-cavity nitride-based semiconductor laser chips are respectively mounted junction-side-down on the corresponding submounts; an optical condenser system collects laser beams emitted from the semiconductor laser chips, and couples the collected laser beams to a multimode optical fiber. A bonding surface of each semiconductor laser chip is bonded to a bonding surface of a corresponding submount through a metalization layer and an Au—Sn eutectic solder layer each of which is divided into areas.

Claims

1. A laser-light source comprising:

a heat-dissipation block made of copper or copper alloy;

a plurality of submounts which are made of a material having a thermal expansion coefficient of 3.5 to 6.0×

10<sup>−

6</sup>/°

C., have a thickness of 200 to 400 micrometers, and are separately formed on said heat-dissipation block;

a plurality of semiconductor lasers each of which is made of a nitride compound, has a single cavity and a form of a chip, and is mounted junction-side-down on one of said plurality of submounts;

a multimode optical fiber; and

an optical condenser system which collects laser beams emitted from said plurality of semiconductor lasers, and couples the collected laser beams to said multimode optical fiber;

wherein each of said plurality of semiconductor lasers and said plurality of submounts has a bonding surface, and the bonding surface of each of the plurality of semiconductor lasers is bonded to the bonding surface of one of the plurality of submounts through a metalization layer and an Au—

Sn eutectic solder layer each of which is divided into a plurality of areas.

2. A laser-light source according to claim 1, wherein each of said plurality of semiconductor lasers contains a light emission region, and said metalization layer and said Au—

Sn eutectic solder layer are separated by a groove which is arranged immediately below the light emission region.

3. A laser-light source according to claim 1, wherein said plurality of submounts are made of AlN.

4. A laser-light source according to claim 1, wherein said plurality of submounts are bonded to the heat-dissipation block with Au—

Sn eutectic solder.

5. A laser-light source according to claim 1, wherein said plurality of semiconductor lasers respectively contain active layers and light emission points, the light emission points of the plurality of semiconductor lasers are arranged on a line parallel to the active layers, said optical condenser system includes a plurality of collimator lenses and a condenser lens, said plurality of collimator lenses are arranged in correspondence with the plurality of semiconductor lasers and respectively collimate said laser beams emitted from the plurality of semiconductor lasers, said condenser lens collects the laser beams collimated by the plurality of collimator lenses, and makes the collimated laser beams converge on an end face of said multimode optical fiber, and said plurality of collimator lenses each have an aperture which has a first diameter parallel to said line and a second diameter perpendicular to said line and greater than the first diameter.

6. A laser-light source according to claim 5, wherein said plurality of collimator lenses are integrally formed into a lens array.

7. A laser-light source according to claim 1, wherein said heat-dissipation block is constituted by a plurality of blocks which are joined.

8. A laser-light source according to claim 1, wherein each of said plurality of semiconductor lasers is a GaN-based compound semiconductor laser.

9. A laser-light source according to claim 1, wherein said multimode optical fiber has a core diameter not greater than 50 micrometers and a numerical aperture not greater than 0.3.

10. A laser-light source according to claim 1, wherein said multimode optical fiber has a core diameter and a numerical aperture, and the core diameter multiplied by the numerical aperture is not greater than 10 micrometers.

11. A laser-light source according to claim 1, wherein said plurality of semiconductor lasers are arranged on a line, and the number of the plurality of semiconductor lasers is three to ten.

12. A laser-light source according to claim 11, wherein said plurality of semiconductor lasers are arranged on a line, and the number of the plurality of semiconductor lasers is six or seven.

13. A laser-light source according to claim 1, wherein each of said plurality of semiconductor lasers has an emission width of 1.5 to 5 micrometers.

14. A laser-light source according to claim 13, wherein each of said plurality of semiconductor lasers has an emission width of 2 to 3 micrometers.

15. A laser-light source according to claim 1, wherein said plurality of semiconductor lasers are fixed so that the plurality of semiconductor lasers are two-dimensionally arranged when viewed from a laser-receiving side.

16. A laser-light source comprising a plurality of laser-light-source portions each of which includes:

a heat-dissipation block made of copper or copper alloy;

a plurality of submounts which are made of a material having a thermal expansion coefficient of 3.5 to 6.0×

10<sup>−

6</sup>/°

C., have a thickness of 200 to 400 micrometers, and are separately formed on said heat-dissipation block;

a plurality of semiconductor lasers each of which is made of a nitride compound, has a single cavity and a form of a chip, and is mounted junction-side-down on one of said plurality of submounts;

a multimode optical fiber; and

an optical condenser system which collects laser beams emitted from said plurality of semiconductor lasers, and couples the collected laser beams to said multimode optical fiber;

wherein each of said plurality of semiconductor lasers and said plurality of submounts has a bonding surface, the bonding surface of each of the plurality of semiconductor lasers is bonded to the bonding surface of one of the plurality of submounts through a metalization layer and an Au—

Sn eutectic solder layer each of which is divided into a plurality of areas, and said multimode optical fiber in the plurality of laser-light-source portions is arranged to constitute a one-dimensional array at least at a light-emission end of the multimode optical fiber.

17. A laser-light source comprising a plurality of laser-light-source portions each of which includes:

a heat-dissipation block made of copper or copper alloy;

a plurality of submounts which are made of a material having a thermal expansion coefficient of 3.5 to 6.0×

10<sup>−

6</sup>/°

C., have a thickness of 200 to 400 micrometers, and are separately formed on said heat-dissipation block;

a plurality of semiconductor lasers each of which is made of a nitride compound, has a single cavity and a form of a chip, and is mounted junction-side-down on one of said plurality of submounts;

a multimode optical fiber; and

an optical condenser system which collects laser beams emitted from said plurality of semiconductor lasers, and couples the collected laser beams to said multimode optical fiber;

wherein each of said plurality of semiconductor lasers and said plurality of submounts has a bonding surface, the bonding surface of each of the plurality of semiconductor lasers is bonded to the bonding surface of one of the plurality of submounts through a metalization layer and an Au—

Sn eutectic solder layer each of which is divided into a plurality of areas, and said multimode optical fiber in the plurality of laser-light-source portions is arranged to constitute a bundle at least at a light-emission end of the multimode optical fiber.

18. An exposure system comprising a plurality of laser-light sources each of which is provided for exposure and includes:

a heat-dissipation block made of copper or copper alloy;

a plurality of submounts which are made of a material having a thermal expansion coefficient of 3.5 to 6.0×

10<sup>−

6</sup>/°

C., have a thickness of 200 to 400 micrometers, and are separately formed on said heat-dissipation block;

a plurality of semiconductor lasers each of which is made of a nitride compound, has a single cavity and a form of a chip, and is mounted junction-side-down on one of said plurality of submounts;

a multimode optical fiber; and

an optical condenser system which collects laser beams emitted from said plurality of semiconductor lasers, and couples the collected laser beams to said multimode optical fiber;

wherein each of said plurality of semiconductor lasers and said plurality of submounts has a bonding surface, the bonding surface of each of the plurality of semiconductor lasers is bonded to the bonding surface of one of the plurality of submounts through a metalization layer and an Au—

Sn eutectic solder layer each of which is divided into a plurality of areas, and said multimode optical fiber in the plurality of laser-light sources is arranged to constitute a one-dimensional array at least at a light-emission end of the multimode optical fiber.

19. An exposure system comprising a plurality of laser-light sources each of which is provided for exposure and includes:

a heat-dissipation block made of copper or copper alloy;

a plurality of submounts which are made of a material having a thermal expansion coefficient of 3.5 to 6.0×

10<sup>−

6</sup>/°

C., have a thickness of 200 to 400 micrometers, and are separately formed on said heat-dissipation block;

a plurality of semiconductor lasers each of which is made of a nitride compound, has a single cavity and a form of a chip, and is mounted junction-side-down on one of said plurality of submounts;

a multimode optical fiber; and

an optical condenser system which collects laser beams emitted from said plurality of semiconductor lasers, and couples the collected laser beams to said multimode optical fiber;

wherein each of said plurality of semiconductor lasers and said plurality of submounts has a bonding surface, the bonding surface of each of the plurality of semiconductor lasers is bonded to the bonding surface of one of the plurality of submounts through a metalization layer and an Au—

Sn eutectic solder layer each of which is divided into a plurality of areas, and said multimode optical fiber in the plurality of laser-light sources is arranged to constitute a bundle at least at a light-emission end of the multimode optical fiber.