Diffractive Beam Splitters: What are They and How they Work

Diffractive Beam Splitters: What are They and How they Work

Diffractive beam splitters are diffractive optical elements (DOEs) used for bifurcating a single collimated laser beam into several beams that have the optical features like the original beam. Often, the beams are bifurcated in a 1D or 2D arrays and can be organized either regularly or irregularly. Diffractive beam splitters can be utilized with the monochromatic light such as a laser beam. The light can be split by percentage of overall intensity, polarization state, and wavelength; however, it retains the same optical characteristics as the input beam.

How They Work

Beam splitters often form the components in high-powered lasers and illumination systems. Industries use them in spectroscopy, optical interferometry, fluorescence applications, instrumentation, and life science. They are specifically used in laser scribing and dicing, medical or aesthetic applications, 3D sensors, laser displays, fiber optics, and IR depth detectors.

Kinds of Beam Splitters

  • Plate beam splitter. This type of beam splitter is used in a lot of life sciences, laser, or imaging applications. Also, it is used in the entertainment and design industry.
  • Dichroic beam splitters. These beam splitters are optimized to offer high transmission of a spectral band while reflecting a second spectral band.
  • Polka-dot beam splitters. They offer a near-constant reflection to transmission ratio with minimal angle sensitivity. The polka dots are made by combining a photolithography process and the vacuum deposition of aluminum that results in a precise pattern of small aluminum dots on the glass substrate.
  • Transmission grating beam splitters. These are used for dividing laser beams and separating multiple laser lines in visible wavelengths.

Diffractive optics is another tool for making an optical system. They are capable of doing some tasks that refractive optics can’t. But, their benefits also come with a cost. DOE comes with some limitations. For instance, they are not easy to give away and often provide the desired results under special conditions.

DOE can bear a strong negative dispersion that is useful in rectifying chromatic abertation when they produce random illumination patters that would be difficult to create with genuine refractive optics. DOEs are like a Fresnal lens, but with tiny features. But, it is important to understand that a Fresnal lens is a diffractive optic. Although it is possible to make the phase profile of DOE to have a more complex optical field, a DOE with a simple focal spot can be made, leading to the creation of a simple lens.