Diffractive beam splitters are a unique type of diffractive optical elements or DOEs that are useful to split or break apart an input laser beam into an array of output beams. The interesting thing is that most characteristics of the input beam remain the same in the output beams, with the exception of the angle of propagation and power. A diffractive beam splitter is also known as a dot generator or fan-out grating.
A diffractive beam splitter can produce any geometrical beams pattern. Based on the diffractive pattern on the optical element, diffractive beam splitters can produce either a one-dimensional beam array or a two-dimensional beam matrix. It is important to note that a monochromatic light beam such as a laser beam is required to use this type of light beam splitter.
The diffractive beam splitters can be designed differently to attain a specific number of beam replicas as well as a specific arrangement of the output beams in the resulting array. Therefore, it is possible to arrange the dots in various configurations, including a hexagonal arrangement, a uniform rectangular grid, and a circular shape. The array can also be not uniform, for instance, some particular dots can be missing in the pattern, dots can be arranged to form a target pattern, or dots can be arranged in a pseudo-random pattern. Irrespective of the arrangement, the design process of the diffractive beam splitter involves an optimization algorithm that determines the discretized phase structure on the DOE.
The Setups for Diffractive Beam Splitters
The typical setup utilizing a diffractive beam splitter includes an input monochromatic beam that travels through a beam splitter, often followed by a lens. Once the input beam navigates through the beam splitter, a predesigned beam array will be generated in the angular space. As the wavelength of the beams determines the angular separation among them, it is best to use lasers with diffractive beam splitters in this setup. In this configuration, a focusing lens is positioned after the beam splitter to generate a desired pattern of spots at the image plane of the lens.
The Applications of Diffractive Beam Splitters
Diffractive beam splitters are useful for a long list of industrial applications. For instance, in the medical field, diffractive beam splitters have significant applications in aesthetic laser treatments, including fractional skin treatments and tattoo removal. These beam splitters are also crucial for monitoring a high-power laser, for 3D sensing and for metrology. Diffractive beam splitters are also used in material processing such as Laser welding, dicing and scribing.
When it comes to calculating the object depth, diffractive beam splitters are used to generate an array of beams to capture the spatial details of an object with an irregular surface. You can also find a similar type of application of diffractive beam splitter in the LIDAR systems for vehicles.
