Flat Top Laser Beam Shapers

Laser systems are now considered a bespoke tool in almost all industry sectors that are currently being used, from micro and macro material processing to medicine. A technology that has bolstered their adaptability to the different requirements in every sector is laser beam shapers, specifically Flat Top Laser beam shapers.

The light radiation emitted by a laser system can be accurately described by a mathematical distribution referred to as Gaussian distribution, which is the same distribution found in statistical analysis, for instance. Well, this distribution is characterised by a peak located on the centre of the beam followed by a slow and smooth fall that expands infinitely, at least in what concerns the mathematical expression. This behaviour can be detrimental to the laser light source for more than one reason. First, the area being treated, be it a piece of metal or a portion of human skin, is not uniformly illuminated.  Secondly, there is the potential for light creeping outside the target area with the subsequent damage that this could cause.

To overcome this hindrance, laser systems integrators resort to a Flat Top Laser beam shaper, also referred to as a Top Hat laser beam shaper. The most common and practical type of Flat Top Laser beam shaper that is adequate to use with monochromatic coherent light, as that from a laser beam, is a diffractive optical element. This is a thin and flat window-like optical component that performs a transformation on an incoming beam. The operating principle behind this component is the wave nature of light in which diffraction,  an interference effect, plays a pivotal role. 

A diffractive optical element, or DOE, which is designed as a Flat Top Laser beam shaper, can modify the inherent Gaussian beam radiation into a Flat Top Distribution which is characterised by a confined area of uniform illumination bounded by a sharp fall, which is in stark contrast to the smooth edges of the original Gaussian beam.  

Depending on the intended application, the area of uniform illumination can be of any desired geometrical shape. It can be rectangular, circular etc. It can even be combined with a beam splitting function to form separated areas with flat top uniform intensity like two flat top round spots, for example.

There is also a refractive Flat Top laser beam shaper which usually consists of two lenses with a distance between them. The advantages of a diffractive laser beam shaper over the refractive one, are first – the perfect anular accuracy of the diffractive element, second – the low tolerances obtained with its semiconductor like methods of fabrication, third – that it occupies less space plus the fact that the design can be much easier and customized.