Optical fiber laser device

Patent metadata

Field	Value
Publication number	US-10862262-B2
Application number	US-201916684040-A
Country	US
Kind code	B2
Filing date	Nov 14, 2019
Priority date	Jul 4, 2014
Publication date	Dec 8, 2020
Grant date	Dec 8, 2020

Abstract

An optical fiber laser device generates laser light by using an optical amplifying fiber as an amplification medium in a laser oscillator and includes: an optical outputting fiber configured to emit laser light to an outside; a return-light-attenuating portion configured to perform an attenuation process to return light propagating through at least the optical outputting fiber in a reverse direction of the laser light; a thermal conversion unit provided at the return-light-attenuating portion and configured to convert the return light into heat; a temperature-monitoring device configured to measure an increase in a temperature, of the return-light-attenuating portion, caused by the heat converted by the thermal conversion unit; and a control unit configured to decrease or stop an output of the laser light when the temperature measured by the temperature-monitoring device becomes a predetermined threshold temperature or higher.

First claim

What is claimed is:

1. An optical fiber laser device for generating laser light by using an optical amplifying fiber as an amplification medium in a laser oscillator and irradiating output laser light, which is output through an optical fiber, to a workpiece via an irradiation head, the optical fiber laser device comprising:
an optical outputting fiber configured to emit laser light;
a return-light-attenuating portion configured to attenuate return light propagating through at least the optical outputting fiber in a reverse direction of the laser light;
a thermal converter provided at the return-light-attenuating portion and configured to convert the return light into heat;
a temperature-monitoring device configured to measure an increase in a temperature, of the return-light-attenuating portion, caused by the heat converted by the thermal conversion unit; and
a controller configured to decrease or stop an output of the laser light when the temperature measured by the temperature-monitoring device becomes a predetermined threshold temperature or higher;
first and second light reflectors; and
a pumping-light multiplexer including a forward-direction-side signal port optical fiber and a reverse-direction-side signal port optical fiber, which configure two end portions of the pumping light multiplexer, and a plurality of pumping-light port optical fibers,
wherein the first light reflector and the second reflector are double-cladding-type optical fibers each having an inner cladding, and the inner cladding propagates light of a pumping-light wavelength in multi-mode,
a core that extends between the forward-direction-side signal port optical fiber and the reverse-direction-side signal port optical fiber and that has single mode propagation characteristics at a laser oscillation wavelength,
the pumping-light port optical fibers are optical fibers each including a core having multi-mode propagation characteristics at the pumping-light wavelength, and
the core, which has the multi-mode propagation characteristics of the optical fibers that have the multi-mode propagation characteristics of the pumping-light port optical fibers, surrounds a core of the forward-direction-side signal port optical fiber.

2. The optical fiber laser device according to claim 1 , wherein the temperature-monitoring device measures a temperature difference between temperatures at a first temperature measurement point where the heat converted by the thermal converter is measured via a thermal conductor and at a second temperature measurement point which is a reference point for measuring a temperature of the optical fiber laser device.

3. The optical fiber laser device according to claim 1 , wherein
the thermal converter is configured with an axis-offset-fusion-splice of optical fibers at the return-light-attenuating portion.

4. The optical fiber laser device according to claim 1 , wherein
the thermal converter is formed of a high loss optical fiber provided at the return-light-attenuating portion.

5. The optical fiber laser device according to claim 1 , wherein
the thermal converter is formed of an intentionally coiled optical fiber provided at the return-light-attenuating portion.

6. The optical fiber laser device according to claim 1 , wherein
the thermal converter is formed of a resin sealing an end of the optical fiber provided at the return-light-attenuating portion.

7. The optical fiber laser device according to claim 1 , wherein
the thermal converter is formed of an irradiation surface of the thermal conductor to which the return light emitted from the end of the optical fiber provided at the return-light-attenuating portion is irradiated.

8. The optical fiber laser device according to claim 1 , wherein
the return-light-attenuating portion is disposed at an upstream side of the laser oscillator in a direction of a laser propagation.

9. The optical fiber laser device according to claim 8 , further comprising a pumping-light multiplexer including an output-side signal port, an input-side signal port, and a plurality of pumping-light ports,
wherein the pumping-light multiplexer is configured to output pumping light input from the pumping-light ports via the output-side signal port connected to the laser oscillator, and
the return-light-attenuating portion is provided at a terminal portion of an optical fiber connected to the input-side signal port of the pumping-light multiplexer.

10. The optical fiber laser device according to claim 8 , further comprising a pumping-light multiplexer including an output-side signal port, an input-side signal port, and a plurality of pumping-light ports,
wherein the pumping-light multiplexer is configured to output pumping light input from the pumping-light ports via the output-side signal port connected to the laser oscillator, and
the return-light-attenuating portion is provided at a terminal portion of an optical fiber connected to the pumping-light port of the pumping-light multiplexer.

11. The optical fiber laser device according to claim 10 , wherein
the return-light-attenuating portion is provided at the terminal portion of the optical fiber connected to one of the pumping-light ports at which an intensity of the return light is maximum out of the pumping-light ports to which a light source outputting the pumping light is not connected.

12. The optical fiber laser device according to claim 8 , wherein
the return-light-attenuating portion is provided at a terminal portion of an optical fiber connected to one whose reflectivity relative to the laser light is higher than the other out of two light-reflecting units configuring the laser oscillator.

13. The optical fiber laser device according to claim 1 , further comprising:
an optical amplifier provided between the laser oscillator and the optical outputting fiber and formed by using an optical amplifying fiber as an amplification medium; and
a second pumping-light multiplexer including an output-side signal port, an input-side signal port, and a plurality of pumping-light ports and configured to output pumping light input from the pumping-light port via the output-side signal port connected to the optical amplifier to introduce the pumping light to the optical amplifying fiber included in the optical amplifier,
wherein the return-light-attenuating portion is provided at a terminal portion of an optical fiber connected to the pumping-light port of the second pumping-light multiplexer.

14. The optical fiber laser device according to claim 1 , wherein the forward-direction-side signal port optical fiber of the pumping-light multiplexer is connected to the double-cladding-type optical fiber so that the core extending from the reverse-direction-side signal port optical fiber to a single mode core and the core extending from each port for pumping light is coupled to an inner cladding, and the double-cladding-type optical fiber is connected to the optical amplifying fiber via the first light-reflecting unit, so that the light input to the reverse-direction-side signal port optical fiber at the laser emission wavelength is propagated to the core of the optical amplifying fiber at a substantially single mode, and the light input to each port for pumping light at the pumping wavelength is propagated to the inner cladding of the optical amplifying fiber in multi-mode.

Assignees

• Furukawa Electric Co Ltd

Inventors

• Kajiwara Koji
• Takagi Takeshi
• Kashiwagi Kousuke
• Hyuga Kazuaki
• Emori Yoshihiro

Classifications

• G02B6/2551

  using thermal methods, e.g. fusion welding by arc discharge, laser beam, plasma torch · CPC title

• G02B6/26

  Optical coupling means (G02B6/36, G02B6/42 take precedence) · CPC title

• H01S3/0014

  Monitoring arrangements not otherwise provided for (photometry G01J1/00, e.g. G01J1/4257; radiation pyrometry G01J5/00; measuring coherence of light G01J9/00; measuring wavelength of light G01J9/00, e.g. G01J9/0246; measuring optical pulses G01J11/00; calorimetrically measuring power of laser beams G01K17/003) · CPC title

• H01S3/1306

  Stabilisation of the amplitude · CPC title

• H01S3/1618

  ytterbium · CPC title