Beam shaper is a diffractive optical element that modifies the intensity distribution of the beam. For example, a flat top beam shaper creates a far field profile with a uniform intensity in its center. Conventional diffractive beam shaper requires accurate alignment and beam control. Input beam diameter and profile have to be exactly right. Unlike the free-space diffractive element, the beam shaper fabricated on the facet of a fiber does not require any alignment. For such beam shaper, the input beam is a fiber mode that does not change in time, providing a reproducibility and long term stability.
The output of a conventional laser or an optical fiber has a Gaussian shape. Many applications, however, require a uniform illumination. One way to achieve this is to pass the light through the beam expander and an aperture. The aperture would remove the edges of the beam so that only a central part of the Gaussian remains. Of course, most of the light is wasted using this approach. Diffractive optics, on the other hand, can convert almost a 100% of light into a flat top profile beam. The disadvantage of diffractive optics is a more complicated optical setup. Indeed, diffractive design heavily relies on the knowledge of the input beam phase and intensity profile. If the input beam is different, output beam would be different as well. Fabricating diffractive optics on a fiber eliminates this problem since the fiber mode profile is known and does not change with time.
- Material processing
Advantages of the beam shaper on a fiber:
- No alignment required
- Long term stability
- Highly reproducible
- Compact size
- Controlled beam divergence
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