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Beam Shapers are, in general, optical components that are used to change the radiance distribution from an input beam. A common beam shaper is a micro lens array in which an input beam is sampled at periodic locations. Then, after some distance propagation, a new beam envelope emerges which averages out any non-uniformity that could have been present at the input beam. Moreover, the new beam radiance exhibits a more Flat Top type of beam distribution.
A micro lens array works solely by the principles dictated by geometrical optics. A more powerful and versatile optical beam shaper is one which works following the laws of the wave theory of light. Such element is referred to as the diffractive beam shaper. As its name implies, the component is set to harness the diffraction effects that take place when a beam encounters an obstacle.
A diffractive beam shaper is a thin optical element that is composed of an array of discrete modulating elements, which can be regarded as the obstacles mentioned above. These obstacles can also be referred to simply as pixels and when a beam traverses such array of pixels, the diffraction effects start taking place, which give rise to a new beam radiance distribution or shape. The advantage of the diffractive beam shaper over the micro lens array resides in the fact that the shapes, or distributions, that can be accomplished with the diffractive beam shaper isvery much open. In fact, any geometrical shape and radiance distribution can be encoded into the pixels of the array. This is done by applying an algorithm that optimizes the value on each pixel such that the end result is the desired output beam distribution.
A diffractive beam shaper can be used to obtained Flat Top Beams from Gaussian beams. The latter is the kind of pattern distribution that is most commonly found in laser systems whereas the former is a distribution characterised by an area of constant radiance surrounded by steep edges. This is the kind of distribution that most applications will benefit from and thus this type of beam transformation is very useful. But the final shape itself does not have to be circular or elliptical, as most beams are. The output beam can be rectangular, square, triangular or any other geometrical shape we can think of. This is the kind of versatility that a diffractive beam shaper can offer.
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