Laser beam expander
Jul. 10, 2021
The laser beam expander improves the working effect of optical instruments by changing the diameter and divergence angle of the laser beam. Its structure is an optical lens group. The optical instrument, which is equipped with a beam expander, is beneficial to reduce loss, bear high-power laser and transmit visible light.
The laser beam emitted from the laser has a certain divergence angle. Through the adjustment of the beam expander, the laser beam becomes a collimated (parallel) beam. Then the beam is focused by a focusing lens and into a high-power density spot.
The laser beam expander is generally composed of fused silica lenses, K9 lenses, zinc selenide lenses (ZnSe lenses) and germanium lenses (Ge lenses). According to the wavelength of the laser, the laser beam expander can be divided into CO2 laser beam expander for 1060nm, Nd : YAG laser beam expander for 1064nm, 532nm and 355nm, and HeNe laser beam expander collimator 633nm.
The laser beam expander usually uses the Galileo telescope system, which is composed of a concave lens and a convex lens, which is generally less than 20 times for beam expansion. The input mirror transmits a virtual focus beam to the output mirror. The two lenses are virtual confocal structures. It has a simple structure, small size and low price. The beam expander has small spherical aberration and low wavefront distortion. Depending on the optical design, the optical lenses include plano concave lenses, double concave lenses, cemented lenses, etc.
Kepler beam expanders are used for beam expansion that requires spatial filtering or large magnification. The Kepler structure generally uses a convex lens as the input lens to send the laser beam focused by the real focal length to the output optical component. In addition, spatial filtering is achieved by placing an aperture at the focal point of the first lens. Kepler beam expanders are mainly used in the light source of helium-neon lasers. The size of the helium-neon laser spot is between 0.8-1.2mm. The spot needs to be enlarged and collimated. The secondary mirror in the beam expansion system can also be replaced by a microscope objective lens. A aperture added at the focal point intercepts the uniform part of the light field.
The adjustment method of the laser beam expander is to fine-tune the distance between the lenses of the laser beam expander, according to the shape of the spot in front of the output lens. In this way, it eliminates the influence of the divergence angle within a certain range, so as to obtain a laser beam with good collimation. Try to make the laser beam travel along the optical axis of the system as much as possible.
The laser beam expander can be used for laser processing, laser marking, laser engraving and laser ranging. For different lasers, laser beam expanders have different optical designs and use magnesium oxide anti-reflection coating to increase the anti-reflection rate.
For many years, CLZ Precision Optics Co., Ltd. is devoted to the processing and production of spherical lenses. Our company specializes in providing plano concave lenses, plano convex lenses, bi-convex lenses, bi-concave lenses and cemented lenses for domestic and foreign customers. We process high-precision spherical lenses and coat them, according to the customer's drawings. If you need related spherical lenses, please contact email@example.com.