Flat Top Laser Beam

Flat Top Laser Beams are beams whose radiance distribution can be described by an area of uniform energy. Outside this area the radiance falls abruptly. This kind of radiance distribution is very convenient for the vast majority of laser applications but at the same time it is not a natural radiance distribution. In fact, most lasers emit according to what they referred to as the Gaussian beam distribution which is characterised by a smooth peak at the centre that gradually and slowly decays with radial coordinate. Not all lasers radiate like this, but it is a fair approximation for many of them.

Thus, if Flat Top Laser beams do not occur naturally, they have to be obtained by some means. For lasers systems, the best option is to use a diffractive optical element that changes the radiance distribution by harnessing the wave nature of light.  Such diffractive optical element is positioned at a specific position along the optical train and then, simply by beam propagation, the desired Flat Top Laser beam is obtained on the treated area.

The advantages offer by Flat Top Laser beams are many. As the radiance is confined to an area which is well bounded, there is no light leakage to adjacent areas. This increases the efficiency of the system. With a Gaussian beam, there is always some light leakage due to the asymptotic behaviour of that type of beams. Flat Top Laser beams also ensured that the treated area is homogenously lit which also works in favour of increasing efficiency and reducing the radiation time.

Flat Top Laser beams do not have to be always circular. In fact, the diffractive optical element can be rectangular, triangular or any other shape. In fact, as long as the radiance is constant  and the edges are very steep, the beam is considered to be a Flat Top Beam. Thus, the diffractive optical element can be designed to produce any of these shapes. This capability opens up the possibility of adapting the Flat Top Laser beam to any practical situation. Flat Top Laser beams can then be used for laser scribing and material processing where the focused spot has to be very precise and light leakage will result in a less than ideal process. They can also be used in medicine, specifically in aesthetic treatment for the skin. Again, the focused spot has to be such that only the area to be treated is reached.

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