A Top Hat laser beams profile is not a beam profile that is found in most lasers, instead, this beam profile is created through beam shaping for a wide range of applications. One of the most common and effective types of laser beam shaping is diffractive beam shaping. Diffractive beam shapers transform the Gaussian profile of a laser beam into a Top Hat beam profile for multiple applications in different fields, including micromachining, scribing, and laser cutting. Manipulating the wave nature of light to achieve a specific irradiance distribution requires diffractive optical elements or DOE. These specific optical elements help transform the single-mode TEM00 light beams to obtain smooth beam shapes with well-defined and sharp edges.
A Gaussian beam profile has a broad transition area with slowly decaying energy in the edges. The problem with the Gaussian beam is that with the instability in pulse energy, the spot width of the beam also changes, as the Gaussian width and height are proportional. This creates instability in the size of the laser-processed zone, with a negative impact on device performance. To avoid this instability, it is essential to transform the Gaussian beam so that it displays. a uniform distribution pattern with an extremely narrow transition area. Once the beam is transformed, the region above a particular progression threshold stays the same irrespective of the change in laser pulse energy.
Top Hat Beam Shapers
A Top Hat laser beam is one type of light beam that offers a consistent irradiance level with extremely sharp edges. The cross-sectional view of this light beam looks like a gentleman’s hat. However, the edges of the Top Hat laser beam are not straight. But rather slope down over a certain width called the transition area.
Top Hat beam shapers’ job is to shape or transform Gaussian laser beams into Top Hat beams. DOEs or diffractive optical elements work as Top Hat beam shapers and help achieve a uniform intensity spot. The transformation process involves a lens system. Where the focusing lens acts to bring the optical component’s far field to the focal plane of the lens, Thus creating a top hat spot at focus. This system is insensitive to the position of the Top Hat DOe vs the lens, thus one can easily integrate Top Hat laser beam shapers into a compact laser system.
Applications
Top Hat laser beams have substantial applications in various industrial sectors. Where coherent, high-quality laser beams are require to concentrate on a particular area of unique size and shape. A custom DOE can shape a Top Hat beam into different distribution patterns. The intensity of the beam depends on the application area.
Some common and useful Top Hat beam applications are laser scribing, laser micro-machining, and sensing. Dicing and electrode exposure in solar panels are crucial examples of laser scribing. Whereas, ablation, kerf removal, and micro-drilling, are examples of laser micro-machining. Microscopy, wafer metrology illumination, and light-sheet cytometry are examples of sensing applications. There are multiple other important applications of Top Hat laser beams, including laser welding, surface treatment, and laser shock peening.
