Optical fibers and optical systems comprising the same
An optical fiber for converting a Gaussian laser beam into a Bessel laser beam may include a first segment optically coupled to a second segment with a transition region, the first segment having a first outer diameter greater than a second outer diameter of the second segment. The first segment may include a first core portion with a first cladding portion extending around the first core portion. The second segment may include a second core portion with a second cladding portion extending around the second core portion. The optical fiber may have a non-axisymmetric refractive index profile or may be coupled to an end cap with a non-axisymmetric refractive index profile.
1. A method for laser processing a transparent workpiece, the method comprising:
forming a contour line in the transparent workpiece, the contour line comprising defects in the transparent workpiece, wherein forming the contour line comprises:
directing a pulsed laser beam provided by a beam source through either:
(a) an optical fiber comprising at least one segment with non-axisymmetric refractive index profile that forms a non-axisymmetric pulsed laser beam, or
(b) an optical fiber generating a ring-shaped beam and an end-cap with non-axisymmetric refractive index profile coupled to the optical fiber generating a ring-shaped beam, such that the end-cap forms a non-axisymmetric pulsed laser beam;
wherein a portion of the non-axisymmetric pulsed laser beam directed into the transparent workpiece generates an induced absorption within the transparent workpiece, the induced absorption producing a defect within the transparent workpiece, and the portion of the pulsed laser beam directed into the transparent workpiece comprises:
a wavelength λ;
an effective spot size w o,eff ; and
a non-axisymmetric beam cross section that comprises a minimum Rayleigh range Z Rx,min in a cross-sectional x-direction and a minimum Rayleigh range Z Ry,min in a cross-sectional y-direction, wherein the smaller of Z Rx,min and Z Ry,min is greater than
F
D
π
w
0
,
eff
2
λ
,
where F D is a dimensionless divergence factor comprising a value of 10 or greater.
2. The method of claim 1 , further comprising translating the transparent workpiece and the non-axisymmetric pulsed laser beam relative to each other along the contour line, thereby laser forming a plurality of defects along the contour line within the transparent workpiece.
3. The method of claim 1 , wherein the dimensionless divergence factor F D comprises a value of from about 50 to about 1500.
4. The method of claim 2 , further comprising directing an infrared laser beam onto the transparent workpiece along or near the contour line to separate the transparent workpiece along the contour line.
5. The method of claim 1 , wherein the beam source comprises a pulsed beam source that produces pulse bursts with from about 1 pulse per pulse burst to about 30 pulses per pulse burst and a pulse burst energy is from about 100 μJ to about 600 μJ per pulse burst.
6. The method of claim 1 , wherein the non-axisymmetric beam cross section of the portion of the non-axisymmetric pulsed laser beam directed into the transparent workpiece comprises a long axis with spot size parameter w o,max and a short axis with spot size parameter w o,min , wherein w o,max is longer than w o,min and an aspect ratio of w o,max to w o,min is greater than 1.3.
7. The method of claim 1 , further comprising a focusing optical component.
8. The method of claim 7 , wherein focusing optical component is a lens with at least one convex surface.
9. The method of claim 1 further comprising an aspheric optical element, wherein the aspheric optical element is a refractive axicon, a reflective axicon, waxicon, negative axicon, a spatial light modulator, a diffractive optic, or a cubically shaped optical element.