The radiance profile of most laser systems can be described in a mathematical formalism known as the Gaussian profile or Gaussian mode. The unique characteristic of a Gaussian profile is that it has a maximum irradiance level at the center that slowly decays towards the edges. The major problem with the Gaussian profile is the non-uniformity in irradiance level, resulting in a substantial energy loss. In many industrial and scientific applications, it is essential to change or transform the inherent radiance pattern of an input laser beam in order to diminish the energy loss and benefit the application. Beam shaping is a method to flatten the central radiance and introduce sharp edges. This is because the lack of sharp or hard edges is the main reason behind the energy loss in a Gaussian profile. The beam shaping method helps to overcome this issue by shaping the beam to attain a constant irradiance.
Different Types of Beam-Shaping Methods
The three main beam shaping methods are – i) single-mode diffractive shaping solutions, ii) multi-mode diffractive shaping laser solutions, and iii) refractive beam shaping. A single-mode diffractive beam shaping can be done in two main different ways, i.e
- Angular Beam Shaping that involves optical elements to provide a Top Hat intensity distribution at a focal length of a diffraction limited lens of the customers, or at infinity.
- Focal Beam Shaping that involves hybrid elements (shaper + lens) to offer a Top Hat intensity distribution at a particular working distance.
On the other hand, multi-mode diffractive laser shaping is mostly done through diffractive beam shaping diffusers, typically with a flat top envelope . The use of Flat Top diffractive diffusers in multi-mode laser solution helps to obtain spot shaping into any desired form, including line, square, rectangular, and round.
Whereas diffractive diffusers and top hat beam shapers follow the principle of diffraction to shape the input light beams, the refractive beam shaping method relies on the principle of refraction. Broadband Diffusers and Micro-Lens Arrays are two crucial beam shapers that modify the input beams by operating on the refractive principle. ordered micro-lens arrays transform the incoherent input beams into a flat top envelope and attain a uniform radiance pattern, but often with some line artifacts. Broadband Diffusers utilize randomized lenslet profiles and thus achieve more uniformity in the irradiance level as well as a smaller amount of order artifacts.
Applications
Beam shaping methods have various industrial and medical applications. Some common industrial applications of beam shaping are material processing such as laser scribing and welding, cutting metal or glass, ablation, etc. In the medical field, beam shaping is crucial for aesthetic treatments such as body countering, hair removal, and tattooing.
