A beam homogenizer or an optical diffuser is an optical component that helps produce a uniform distribution pattern by modifying an input laser beam. When a single-mode or multi-mode incident laser beam is projected onto the homogenizer, it applies a quasi-random or random modification method to diffuse the irregularities of the input beam. As a result, the output beam achieves a precise and constant intensity profile at the focal plane or far field. While the intensity profile remains consistent within a certain area, you might find an extremely low intensity outside that area. This article will help you learn about the operating principle of beam homogenizers, different types of laser beam homogenizers, and their applications in different fields.
The Operating Principle of Homogenizer
Once you know the homogenizer definition, it’s time to understand its operating principle. The operating principle is based on spreading of the concentrated laser energy at the beam’s center. To uniformly spread the energy of the laser beam, the beam homogenizer scatters the input beam in a way that the input beam overlaps itself multiple times, resulting in a unique beam whose divergence angle is larger than the original input beam. Therefore, a rough or ground glass can simply work as a beam homogenizer. However, rough glass will be a poor and inefficient beam homogenizer without any shaping beyond the Gaussian shape.
As the required optical efficiency and homogenization quality are different for different applications, there are a variety of approaches for beam homogenizing and each approach utilizes a unique principle.
Here are some popular beam-homogenizing approaches-
- Broadband diffusers or random microlens arrays
- Fly eye diffusers-Microlens array pair situated in a conjugate plane
- Multifaceted mirrors
- Rotating diffuser plates
- Diffractive homogenizers
- Multimode fibers or waveguides
Types of Beam Homogenizers
There are major types of beam homogenizers, such as broadband diffusers, diffractive homogenizers, and microlens arrays.
Broadband Diffusers: This beam homogenizer can work on a laser system of different wavelengths and shapes and evens out the input beam, ensuring consistent output in one optical setup, irrespective of the wavelengths of the laser beams.
Diffractive Homogenizers: This type of beam homogenizer can split an input beam into different directions, resulting in various shapes and intensities. This beam homogenizer is useful to have strong control over the size, angle, and distribution of the beam.
Microlens Arrays: This beam homogenizer consists of an array of tiny lenses. Each lens captures a certain portion of the input beam and projects it, overlapping with the light beam from neighboring lenses to produce a uniform beam.
Applications
Beam homogenizers have plenty of applications in laser systems, including
- In medical and aesthetic treatments, such as tattoo removal, hair removal, etc.
- In laser projection for light shows and displays
- In material processing, such as welding, remelting, metal hardening, laser cleaning, etc.
- In Time-of-flight or ToF 3D sensing.