Laser apparatus and laser materials processing apparatus provided with same

1. A laser apparatus comprising:

an active fiber having a core, a first end and second end;

a passive fiber connected to the second end of the active fiber, the passive fiber having a core and an inner cladding surrounding the core;

a first laser light source that emits a first laser beam into the core of the active fiber; and

a second laser light source that emits a second laser beam that is coupled into the inner cladding of the passive fiber,

wherein the second laser light source is located at a downstream side of the first laser light source,

wherein a refractive index of the core of the passive fiber is larger than a refractive index of the inner cladding of the passive fiber, and

wherein a power density distribution of each of the first laser beam and the second laser beam which are emitted from an output end of the passive fiber is a multi-mode.

2. 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.

3. The laser apparatus according to claim 2 , wherein a wavelength λ1 of the first laser beam and a wavelength λ2 of the second laser beam satisfy 0.6≦λ2/λ1<0.97.

4. The laser apparatus according to claim 1 , wherein a wavelength λ1 of the first laser beam and a wavelength λ2 of the second laser beam satisfy 0.6≦2/λ1≦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 any one of the preceding claims; 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 ·( D 2− D 1)/2>0.2·(1/ A )·κ·{ρ C p ( T m −T 0 )+μ L m }(1)

Here,

D 1 : Spot diameter of the first laser beam,

D 2 : 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,

T 0 : Initial temperature of the workpiece (room temperature), and

L m : Latent heat of fusion of the workpiece.

8. The laser materials processing apparatus according to claim 5 , wherein the power density I b of the second laser beam satisfies the following Formula (1):

I b ·( D 2− D 1)/2>0.2·(1/ A )·κ·{ρ C p ( T m −T 0 )+μ L m }(1)

Here,

D 1 : Spot diameter of the first laser beam,

D 2 : 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,

T 0 : Initial temperature of the workpiece (room temperature), and

L m : Latent heat of fusion of the workpiece.

9. The laser apparatus according to claim 1 , further comprising a multi coupler connecting the second laser light source to the passive fiber.

10. The laser apparatus according to claim 1 , wherein a diameter of the core of the passive fiber is equal to or larger than a diameter of the core of the active fiber.