LASER APPARATUS AND LASER MATERIALS PROCESSING APPARATUS PROVIDED WITH SAME

• US 20130215914A1
• Filed: 10/18/2010
• Published: 08/22/2013
• Est. Priority Date: 10/18/2010
• Status: Active Grant

• Current Assignee: Nippon Steel Corporation
• Original Assignee: Nippon Steel & Sumitomo Metal Corporation (Nippon Steel Corporation)
• Inventors: Imai, Hirofumi, Hirano, Koji
• Granted Patent: US 9,172,202 B2
• Time in Patent Office: Days
• US Class Current: 372/6
• CPC Class Codes: B23K 26/0613 having a common axis B23K26/0619 takes precedence
• 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 3/06716 Fibre compositions per se C03C13/04or doping with active elements lasing materials in general H01S3/14
• 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 3/094011 with bidirectional pumping, i.e. with injection of the pump light from both two ends of the fibre
• CPC Class Codes: H01S 3/09408 Pump redundancy
• CPC Class Codes: H01S 3/175 phosphate glass
• CPC Class Codes: H01S 3/23 Arrangements of two or more lasers not provided for in groups H01S3/02 - H01S3/22, e.g. tandem arrangements of separate active media

Abstract

A laser apparatus of the present invention has a first laser oscillator that emits a first laser beam; a passive fiber that is a double-clad fiber that transmits the first laser beam through a core; and a second laser oscillator that emits a second laser beam that is coupled into inner cladding of the passive fiber. Additionally, a laser materials processing apparatus of the present invention is provided with the laser apparatus; and an irradiation optical system having a collimating lens and a condenser lens.

Claims

1. A laser apparatus comprising:

a first laser oscillator that emits a first laser beam;

a passive fiber that is a double-clad fiber that transmits the first laser beam through a core; and

a second laser oscillator that emits a second laser beam that is coupled into an inner cladding of the passive fiber.

2. The laser apparatus according to claim 1,

wherein the first laser oscillator has a laser resonator having an active fiber that is a double-clad fiber in which rare earth elements are doped to a core, and a pumping light source that emits pumping light that is coupled into an inner cladding of the active fiber, and

wherein the passive fiber is connected to a downstream side of the active fiber.

3. The laser apparatus according to claim 1,

wherein an incident angle θ

_FL of the first laser beam that is coupled into a core of the passive fiber is smaller than an incident angle θ

_LD of the second laser beam that is coupled into the inner cladding of the passive fiber.

4. The laser apparatus according to claim 1,

wherein a wavelength λ

1 of the first laser beam and a wavelength λ

2 of the second laser beam satisfy 0.6≦

λ

2/λ

1≦

0.97.

5. A laser materials processing apparatus that condenses a laser beam and irradiates a workpiece with the laser beam, comprising:

the laser apparatus according to claim 1; and

an irradiation optical system having a collimating lens and a condenser lens.

6. The laser materials processing apparatus according to claim 5,

wherein a power density I_b of the second laser beam is smaller than a power density I_a of the first laser beam.

7. The laser materials processing apparatus according to claim 6,

wherein the power density I_b of the second laser beam satisfies the following Formula (1):

I_b·

(D2−

D1)/2>

0.2·

(1/A)·

κ

·

{ρ

C_p(T_m−

T₀)+ρ

L_m} 

 

(1)

Here,

D1;

Spot diameter of the first laser beam,

D2;

Spot diameter of the second laser beam,

A;

Absorption factor of the second laser beam to the workpiece,

κ

;

Thermal diffusion coefficient of the workpiece,

ρ

;

Density of the workpiece,

C_p;

Specific heat of the workpiece,

T_m;

Melting point of the workpiece,

T₀;

Initial temperature of the workpiece (room temperature), and

L_m;

Latent heat of fusion of the workpiece.

8. A laser materials processing apparatus that condenses a laser beam and irradiates a workpiece with the laser beam, comprising:

the laser apparatus according to claim 2; and

an irradiation optical system having a collimating lens and a condenser lens.

9. The laser materials processing apparatus according to claim 8,

wherein a power density I_b of the second laser beam is smaller than a power density I_n of the first laser beam.

10. The laser materials processing apparatus according to claim 9,

wherein the power density I_b of the second laser beam satisfies the following Formula (1):

I_b·

(D2−

D1)/2>

0.2·

(1/A)·

κ

·

{ρ

C_p(T_m−

T₀)+ρ

L_m} 

 

(1)

Here,

D1;

Spot diameter of the first laser beam,

D2;

Spot diameter of the second laser beam,

A;

Absorption factor of the second laser beam to the workpiece,

κ

;

Thermal diffusion coefficient of the workpiece,

ρ

;

Density of the workpiece,

C_p;

Specific heat of the workpiece,

T_m;

Melting point of the workpiece,

T₀;

Initial temperature of the workpiece (room temperature), and

L_m;

Latent heat of fusion of the workpiece.

11. A laser materials processing apparatus that condenses a laser beam and irradiates a workpiece with the laser beam, comprising:

the laser apparatus according to claim 3; and

an irradiation optical system having a collimating lens and a condenser lens.

12. The laser materials processing apparatus according to claim 11,

wherein a power density I_b of the second laser beam is smaller than a power density I_a of the first laser beam.

13. The laser materials processing apparatus according to claim 12,

wherein the power density I_b of the second laser beam satisfies the following Formula (1):

I_b·

(D2−

D1)/2>

0.2·

(1/A)·

κ

·

{ρ

C_p(T_m−

T₀)+ρ

L_m} 

 

(1)

Here,

D1;

Spot diameter of the first laser beam,

D2;

Spot diameter of the second laser beam,

A;

Absorption factor of the second laser beam to the workpiece,

κ

;

Thermal diffusion coefficient of the workpiece,

ρ

;

Density of the workpiece,

C_p;

Specific heat of the workpiece,

T_m;

Melting point of the workpiece,

T₀;

Initial temperature of the workpiece (room temperature), and

L_m;

Latent heat of fusion of the workpiece.

14. A laser materials processing apparatus that condenses a laser beam and irradiates a workpiece with the laser beam, comprising:

the laser apparatus according to claim 4; and

an irradiation optical system having a collimating lens and a condenser lens.

15. The laser materials processing apparatus according to claim 14,

wherein a power density I_b of the second laser beam is smaller than a power density I_a of the first laser beam.

16. The laser materials processing apparatus according to claim 15,

wherein the power density I_b of the second laser beam satisfies the following Formula (1):

I_b·

(D2−

D1)/2>

0.2·

(1/A)·

κ

·

{ρ

C_p(T_m−

T₀)+ρ

L_m} 

 

(1)

Here,

D1;

Spot diameter of the first laser beam,

D2;

Spot diameter of the second laser beam,

A;

Absorption factor of the second laser beam to the workpiece,

κ

;

Thermal diffusion coefficient of the workpiece,

ρ

;

Density of the workpiece,

C_p;

Specific heat of the workpiece,

T_m;

Melting point of the workpiece,

T₀;

Initial temperature of the workpiece (room temperature), and

L_m;

Latent heat of fusion of the workpiece.