# US 2019/0319431 A1 · Laser module

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- Number: US 2019/0319431 A1
- Document ID: US20190319431A1
- Status: Published application
- Kind: A1
- Application number: 16/347,646
- Filed: 2017-11-16
- Published: 2019-10-17
- Earliest claimed: 2016-11-16
- Assignees: Fujikura Ltd.
- Applicants: Fujikura Ltd.
- Inventors: Ken Katagiri
- Web page: https://patentgrep.com/patent/US20190319431A1

## CPC

- H01S 5/4012: {Beam combining, e.g. by the use of fibres, gratings, polarisers, prisms}
- G02B 6/4207: {with optical elements reducing the sensitivity to optical feedback (anti-reflection devices specially adapted for lasers, see H01S3/0064)}
- G02B 6/4296: {coupling with sources of high radiant energy, e.g. high power lasers, high temperature light sources}
- H01S 5/02251: using optical fibres
- H01S 5/02253: using lenses
- H01S 5/02255: using beam deflecting elements
- H01S 5/02326: Arrangements for relative positioning of laser diodes and optical components, e.g. grooves in the mount to fix optical fibres or lenses
- H01S 5/0239: Combinations of electrical or optical elements
- H01S 5/4031: {Edge-emitting structures}
- H01S: DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

An embodiment of the present invention provides a laser module having a longer average device life as compared to a conventional laser module. A laser module (1) includes: a plurality of laser diodes (LD1 to LD6) emitting laser beams; and an optical fiber (OF), the laser beams being caused to enter the optical fiber (OF), the laser diodes (LD1 to LD6) being arranged such that among light beams constituting return light emitted from the optical fiber (OF), a paraxial beam does not meet active layers of the laser diodes (LDi) at respective exit end surfaces of the laser diodes (LDi), the paraxial beam having been emitted from the optical fiber (OF) at an emission angle θ of not more than θ1 which is given by the following Formula (A): [ Math .  1 ]  θ 1 = Arcsin  ( NA ) 3  2  ln   2 , ( A ) where NA is a numerical aperture of the optical fiber.

## Claims

### Claim 1

A laser module comprising:
a plurality of laser diodes emitting laser beams; and
an optical fiber,
the laser beams being caused to enter the optical fiber,
the laser diodes being arranged such that among light beams constituting return light emitted from the optical fiber, a paraxial beam does not meet active layers of the laser diodes at respective exit end surfaces of the laser diodes, the paraxial beam having been emitted from the optical fiber at an emission angle θ of not more than θ1 which is given by the following Formula (A):
[
Math
.

1
]

θ
1
=
Arcsin

(
NA
)
3

2

ln


2
,
(
A
)
where NA is a numerical aperture of the optical fiber.

### Claim 2 (depends on 1)

The laser module as set forth in claim 1, wherein:
the laser diodes are spatially clustered.

### Claim 3 (depends on 1)

The laser module as set forth in claim 1, wherein:
the laser diodes are arranged such that (a) the respective exit end surfaces of the laser diodes are provided on a certain line segment or a certain circular arc and (b) a distance between adjacent laser diodes which belong to different clusters is larger than a distance between adjacent laser diodes which belong to one cluster.

### Claim 4 (depends on 3)

The laser module as set forth in claim 3, wherein:
the laser diodes are 2M laser diodes, where M is a natural number of not less than 2; and
the 2M laser diodes are arranged such that the respective exit end surfaces of the laser diodes are provided at 2M points x1, x2, . . . , xM, and xN−M+1, xN−M+2, . . . , xN selected from among N points x1, x2, . . . , xN, where N is a natural number of not less than 2M+1, the N points x1, x2, . . . , xN being provided at equal intervals on the certain line segment or the certain circular arc and arranged such that a relation of optical path lengths Lj from respective points xj to an entrance end surface of the optical fiber is L1>L2>. . . >LN.

### Claim 5 (depends on 3)

The laser module as set forth in claim 3, wherein:
the laser diodes are 2M−1 laser diodes, where M is a natural number of not less than 2; and
the 2M−1 laser diodes are arranged such that the respective exit end surfaces of the laser diodes are provided at 2M−1 points x1, x2, . . . , xM, and xN−M+2, xN−m+3, . . . , xN selected from among N points x1, x2, . . . , xN, where N is a natural number of not less than 2M+1, the N points x1, x2, . . . , xN being provided at equal intervals on the certain line segment or the certain circular arc and arranged such that a relation of optical path lengths Lj from respective points xj to an entrance end surface of the optical fiber is L1>L2>. . . >LN.

### Claim 6

A laser module comprising:
2M−1 laser diodes emitting laser beams, where M is a natural number of not less than 2; and
an optical fiber,
the laser beams being caused to enter the optical fiber,
the 2M−1 laser diodes being spatially clustered such that among light beams constituting return light emitted from the optical fiber, a light beam on an optical axis does not meet active layers of the 2M−1 laser diodes at respective exit end surfaces of the 2M−1 laser diodes, the light beam on the optical axis being emitted at an emission angle of 0°,
the 2M−1 laser diodes being arranged such that the respective exit end surfaces of the 2M−1 laser diodes are provided at 2M−1 points x1, x2, . . . , xM, and xN−M+2, xN−M+3, . . . , xN selected from among N points x1, x2, . . . , xN, where N is a natural number of not less than 2M+1, the N points x1, x2, . . . , xN being provided at equal intervals on a certain line segment or a certain circular arc and arranged such that a relation of optical path lengths Lj from respective points xj to an entrance end surface of the optical fiber is L1>L2>. . . >LN.