Optical fiber laser device

• US 10,530,117 B2
• Filed: 12/29/2016
• Issued: 01/07/2020
• Est. Priority Date: 07/04/2014
• Status: Active Grant

• Current Assignee: Furukawa Electric Company Limited
• Original Assignee: Furukawa Electric Company Limited
• Inventors: Kajiwara, Koji, Takagi, Takeshi, Kashiwagi, Kousuke, Hyuga, Kazuaki, Emori, Yoshihiro
• Primary Examiner(s): Niu, Xinning(Tom)
• Application Number:
  US15/393,709
• Publication Number:
  US 20170110847A1
• Time in Patent Office: 1,104 Days
• CPC Class Codes: G02B 6/02 Optical fibres with cladding with or without a coating
• CPC Class Codes: G02B 6/2551 using thermal methods, e.g. fusion welding by arc discharge, laser beam, plasma torch
• CPC Class Codes: G02B 6/26 Optical coupling means G02B6/36, G02B6/42 take precedence
• CPC Class Codes: G02B 6/264 with optical elements between opposed fibre ends which perform a function other than beam splitting having lens focusing means G02B6/32; utilising prism or grating G02B6/34
• CPC Class Codes: G02B 6/266 the optical element being an attenuator
• CPC Class Codes: H01S 3/0014 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 Class Codes: H01S 3/005 Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping shaping laser beam for working metal or other materials B23K26/06; optical elements, systems or apparatus in general G02B
• CPC Class Codes: H01S 3/0675 Resonators including a grating structure, e.g. distributed Bragg reflectors [DBR] or distributed feedback [DFB] fibre lasers
• CPC Class Codes: H01S 3/06754 Fibre amplifiers H01S3/06708 takes precedence
• CPC Class Codes: H01S 3/094011 with bidirectional pumping, i.e. with injection of the pump light from both two ends of the fibre
• CPC Class Codes: H01S 3/09415 the pumping beam being parallel to the lasing mode of the pumped medium, e.g. end-pumping
• CPC Class Codes: H01S 3/1022 by controlling the optical pumping
• CPC Class Codes: H01S 3/1305 Feedback control systems
• CPC Class Codes: H01S 3/1306 Stabilisation of the amplitude
• CPC Class Codes: H01S 3/1618 ytterbium

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.

Claims

1. An optical fiber laser device for generating laser light by using an optical amplifying fiber as an amplification medium in a laser oscillator, the optical fiber laser device comprising:

an optical outputting fiber configured to output laser light to an outside in a forward direction, the optical outputting fiber being a substantially single mode fiber; and

a return-light-attenuating portion formed of an optical attenuating fiber coiled for a plurality of coplanar rounds, wherein

a bending radius of the optical attenuating fiber varies every round of the plurality of coplanar rounds, and

a bending loss in return light is greater than a bending loss in visible light, the return light being infrared light propagating through the optical outputting fiber in a reverse direction of the laser light.

2. The optical fiber laser device according to claim 1, wherein the return-light-attenuating portion is connected to an optical fiber disposed at an upstream side relative to a reflection unit, of the laser oscillator, having high reflectivity.

3. The optical fiber laser device according to claim 2, wherein the return-light-attenuating portion is connected to an optical fiber at a reverse direction side relative to the reflection unit via a signal port optical fiber of a pumping-light multiplexer for introducing pumping light used for laser oscillation of the laser oscillator to the optical amplifying fiber.

4. The optical fiber laser device according to claim 2, wherein the return-light-attenuating portion is connected to an optical fiber at a reverse direction side relative to the reflection unit via a pumping light port of the pumping-light multiplexer for introducing pumping light used for laser oscillation of the laser oscillator to the optical amplifying fiber.

5. The optical fiber laser device according to claim 1, wherein the return-light-attenuating portion is connected to an optical fiber split from an optical multiplexer/demultiplexer provided in a middle of the optical outputting fiber.

6. The optical fiber laser device according to claim 1, further comprising a visible-light-emitting portion introducing the visible light to the optical outputting fiber via the return-light-attenuating portion.

7. The optical fiber laser device according to claim 6, wherein a bend edge wavelength of the optical attenuating fiber is shorter than a wavelength of the return light.

8. The optical fiber laser device according to claim 6, wherein the optical attenuating fiber is configured to propagate the visible light in a substantially single mode.

9. The optical fiber laser device according to claim 8, wherein the optical attenuating fiber is configured to propagate a red-color light in a substantially single mode.

10. The optical fiber laser device according to claim 1, wherein a terminal of the return-light-attenuating portion is sealed by a resin.

11. The optical fiber laser device according to claim 1, wherein an optical sensor conducting a photoelectric conversion is connected to a terminal of the return-light-attenuating portion.

12. An optical fiber laser device for generating laser light by using an optical amplifying fiber as an amplification medium in a laser oscillator, the optical fiber laser device comprising:

an optical outputting fiber configured to output the laser light to an outside in a forward direction, the optical outputting fiber being a substantially single mode fiber; and

a return-light-attenuating portion configured to attenuate an optical intensity of return light including infrared light propagating a core of the optical outputting fiber in a reverse direction and emit the attenuated return light from an end portion on an opposite side to the optical outputting fiber, wherein

the return-light-attenuating portion includes;

a return light propagation loss portion made of an optical attenuating fiber coiled for a plurality of coplanar rounds, the optical attenuating fiber giving a loss to the return light continuously in a direction of propagation of the return light, a bending radius of the optical attenuating fiber varying every round of the plurality of coplanar rounds

wherein a major portion of the return light is attenuated and subjected to thermal conversion at the return light propagation loss portion, and

only residual light, of which intensity is minute, after being attenuated is output from an end portion of the return light propagation loss portion.

13. The optical fiber laser device according to claim 12, wherein

optical attenuating fiber includes a core connected to a core of an optical fiber included in the laser oscillator of the optical fiber laser device, and

the major portion of the return light is attenuated at the core included in the return light propagation loss portion.

14. The optical fiber laser device according to claim 13, wherein a loss, of the core of the optical fiber included in the return light propagation loss portion, at a wavelength of an infrared laser light output from the optical outputting fiber is greater than a loss at a visible wavelength bandwidth.

15. The optical fiber laser device according to claim 14, wherein the core of the optical fiber included in the return light propagation loss portion has single mode propagation characteristics at the visible wavelength bandwidth.

16. The optical fiber laser device according to claim 12, further comprising a visible-light-emitting portion configured to introduce the visible light to the optical outputting fiber via the return-light-attenuating portion.

17. The optical fiber laser device according to claim 12, wherein an optical sensor conducting a photoelectric conversion is connected to a terminal of the return-light-attenuating portion.