Fiber laser apparatus and laser processing method

• US 20080123694A1
• Filed: 06/13/2007
• Published: 05/29/2008
• Est. Priority Date: 06/13/2006
• Status: Active Grant

• Current Assignee: Sumitomo Electric Industries Limited (Sumitomo Corporation)
• Original Assignee: Sumitomo Electric Industries Limited (Sumitomo Corporation)
• Inventors: Kakui, Motoki, Tamaoki, Shinobu, Nakamae, Kazuo
• Granted Patent: US 8,008,600 B2
• Time in Patent Office: Days
• US Class Current: 372/6
• CPC Class Codes: G02B 6/03633 arranged - -
• CPC Class Codes: G02B 6/4296 coupling with sources of high radiant energy, e.g. high power lasers, high temperature light sources
• CPC Class Codes: H01S 3/06758 Tandem amplifiers
• CPC Class Codes: H01S 3/0809 Two-wavelenghth emission
• CPC Class Codes: H01S 3/094007 Cladding pumping, i.e. pump light propagating in a clad surrounding the active core
• CPC Class Codes: H01S 3/2308 Amplifier arrangements, e.g. MOPA

Abstract

The invention relates to a fiber laser apparatus having a structure that enables efficient laser processing for an object and to a laser processing method. The fiber laser apparatus comprises an amplifying section for amplifying seed light by cladding-pumping, and has a structure for further using a residual component of pumping light for cladding-pumping in order to heat the object. In particular, a guiding optical fiber is provided between an amplifying optical fiber of the amplifying section and an output optical system converging the single-mode amplified seed light on the object, the guiding optical fiber serving to increase the degree of freedom in arranging the output optical system. The guiding optical fiber has a structure enabling the single-mode propagation of the amplified seed light outputted from the amplifying optical fiber and multimode propagation of the residual pumping light. Because the object is irradiated with the converged amplified seed light, while being heated with the residual pumping light outputted from the output optical system, even an object with a complex shape can be subjected to efficient laser processing.

Claims

1. A fiber laser apparatus comprising:

a seed light source outputting seed light;

an amplifying section for amplifying the seed light by cladding-pumping, said amplifying section including;

an amplifying optical fiber having a core extending along a predetermined axis, an inner cladding provided on an outer periphery of said core and having a refractive index lower than that of said core, and an outer cladding provided on an outer periphery of said inner cladding and having a refractive index lower than that of said inner cladding;

an pumping light source outputting pumping light; and

an optical multiplexers for supplying the seed light from said seed light source to said core of said amplifying optical fiber and supplying the pumping light from said pumping light source to said inner cladding of said amplifying optical fiber, whereby said amplifying optical fiber outputs single-mode amplified seed light that is amplified by cladding-pumping together with multimode residual pumping light;

an output optical system irradiating an object with the single-mode amplified seed light and multimode residual pumping light that are outputted from said amplifying optical fiber, said output optical system converging the single-mode amplified seed light on the object; and

a guiding optical fiber, for guiding the single-mode amplified seed light and multimode residual pumping light that are outputted from said amplifying optical fiber to said output optical system, provided between said amplifying optical fiber and said output optical system, said guiding optical fiber having a core extending along a predetermined axis, an inner cladding provided on an outer periphery of said core and having a refractive index lower than that of said core, and an outer cladding provided on an outer periphery of said inner cladding and having a refractive index lower than that of said inner cladding, whereby the single-mode amplified seed light outputted from said amplifying optical fiber propagates mainly in said core of said guiding optical fiber, and the multimode residual pumping light outputted from said amplifying optical fiber propagates mainly in said core and inner cladding of said guiding optical fiber.

2. A fiber laser apparatus according to claim 1, further comprising a heating light source outputting multimode light with a wavelength different from that of the pumping light, as heating light for heating the object,

wherein the heating light from said heating light source is supplied, from a light incidence end of said amplifying optical fiber, into said amplifying optical fiber through said optical multiplexer.

3. A fiber laser apparatus according to claim 2, wherein said heating light source outputs continuous light as multimode heating light.

4. A fiber laser apparatus according to claim 1, further comprising:

a heating light source outputting multimode light with a wavelength different from that of the pumping light, as heating light for heating the object; and

a different optical multiplexer provided between said amplifying optical fiber and said guiding optical fiber,

wherein the heating light from said heating light source is supplied, from a light incidence end of said guiding optical fiber, into said guiding optical fiber through said different optical multiplexer.

5. A fiber laser apparatus according to claim 2, wherein said heating light source outputs continuous light as multimode heating light.

6. A fiber laser apparatus according to claim 1, wherein said core of said amplifying optical fiber is doped with ytterbium of a concentration-length product such that unsaturated absorption of said amplifying optical fiber becomes 3 dB or more but 13 dB or less at a wavelength of the pumping light.

7. A laser processing method comprising the steps of:

preparing a fiber laser apparatus according to claim 1;

arranging said output optical system in said fiber laser apparatus such that a processing area of the object matches a convergence point of single-mode amplified seed light that is outputted from said fiber laser apparatus; and

irradiating the object with the single-mode amplified seed light together with the multimode residual pumping light, both single-mode amplified seed light and multimode residual pumping light having been guided from said amplifying optical fiber in said fiber laser apparatus into said output optical system, through said guiding optical fiber in said fiber laser apparatus.

8. A laser processing method according to claim 7, wherein, during simultaneous irradiation with the single-mode amplified seed light and the multimode residual pumping light, the object is further irradiated, through said output optical system, with multimode heating light of a wavelength different from that of the pumping light.

9. A laser processing method according to claim 8, wherein the multimode heating light has a wavelength of 400 nm or more but 980 nm or less.

10. A laser processing method according to claim 7, wherein the processing area of the object irradiated with the multimode heating light is from an aluminum material.