Beam homogenizer for hollow-fiber delivery system of excimer laser light

Abstract

A beam homogenizer for a hollow-fiber-based, UV laser delivery system is proposed. A rectangular glass waveguide with an inner aluminum coating that has a 1-mm square cross section is attached at the output end of the circular-core hollow fiber with a 1-mm inner diameter. The rectangular waveguide generates a number of higher-order modes and results in a uniform top-hat profile. The configuration of the waveguide is designed by a ray-tracing technique so that both the low transmission loss and the high uniformity in the output beam are obtained. The fabricated waveguide shows a low loss of 0.4 dB, and the intensity variation coefficient is 7%. The output beam from the rectangular waveguide is expanded by a lens to the size larger than 10-mm square. It is also shown that the profile does not change with the bending condition.

Top hat single-mode polarization maintaining fiber and polarizing numerical design

“…An elegant solution is obviously an all fiber system delivering directly a top hat beam profile. This can be done by using a highly multimode fiber but it requires mixing a high enough number of modes and leads to a very low depth of focus [5,6]. The ideal solution is thus to use a single-mode fiber delivering a top hat profile.…”

Industrial mJ-class all-fiber front end with spatially coherent top-hat beam output used as seeder for high power laser

“…To overcome alignment difficulties inherent to free space beam shaping, an elegant solution is to use an optical fiber directly delivering the desired spatial beam shape. Of course, an efficient solution is to use highly-multimode fibers [5][6][7] but it leads to a low spatial coherence inducing very low depth of focus which is often detrimental for many applications, such as cutting or marking. To overcome these drawbacks, single-mode fibers supporting a flattened fundamental mode have been developed [8][9][10][11].…”

Top-hat beam output with 100 μJ temporally shaped narrow-bandwidth nanosecond pulses from a linearly polarized all-fiber system

“…To overcome alignment difficulties inherent to free space beam shaping, an elegant solution is to use an optical fiber directly delivering the desired spatial beam shape. Of course, an efficient solution is to use highly multimode fibers [4][5][6] but it leads to a low spatial coherence inducing very low depth of focus which is often detrimental for many applications, such as cutting or marking. To overcome these drawbacks, single-mode fibers supporting a flattened fundamental mode have been developed [7][8][9][10].…”