What Is a Beam Expander?

1. Brief introduction of beam expander

A light or laser beam expander is a scientific instrument that can expand the input beam of parallel light or laser into a larger output beam. In terms of usage, the instrument is similar to a telescope and produces linear telescopic rays or prism rays, such as rays that can be seen when light reflects off the crystal face of a crystal. Laser beam expanders are used in nearly ten scientific applications in laser physics and their output rays for measurement, such as laser micromachining, solar cell slicing, remote sensing, and scientific experiments in many other fields. Without affecting the chromaticity, their beam magnifications purposely avoid focusing, allowing for the smallest applications (such as microscopes) to the largest astronomical measurements. Developed by mature telescope optical systems, they have high transmittance and low distortion.

Most of the functions available in laser beam expanders are suitable for standard entrance apertures, and can retain accurate beams regardless of wavelength. The laser beam expanders can process light from the ultraviolet spectrum, pass through all visible regions and enter the infrared region, and can reduce the length of the telescope. They are designed for variable and fixed output configurations with column adjustment controls.

For some backgrounds, optical telescopes are fire-resistant or reflective. Refracting telescopes refract light through lenses that bend or refract light, while reflecting telescopes use large optical lenses to reflect light. The laser beam expander is essentially a telescope, and its principle is that the beam divergence and the beam expansion ratio have the same factor. The lower power beam expander is based on the Galileo telescope design, with negative input and positive output lens groups. However, there are also Kepler telescope designs, which have a pinhole focusing lens in the middle and two positive lenses, which are very long and scalable.

The place of the image lens and objective lens produced by the design of the laser beam expanders is opposite to that in the Kepler telescope. The input cylindrical beam is focused to a point between the lenses, where the laser heat accumulates and heats the air, causing wavefront distortion. Therefore, Galileo design is usually preferred to prevent distortion. Since the laser beam expander will amplify the laser input with the set expansion power, it will reduce the divergence of the beam on the output with the same power, and at a larger distance, the cylindrical beam will be smaller.

2. The design of beam expander

The so-called hybrid out-of-cavity optical design in the beam expander uses a convex lens after the standard beam expander. Its shape is similar to the curvature of the human eye, resulting in a multiple prism effect. These expanded beams can be emitted for a long distance, but when viewed from an angle, they appear very thin. These line illuminations are used in interferometric procedures for optical and engineering metrology measurements. They are also used in nuclear, particle and plasma physics.