Retroreflectors Align Lasers for Remote Sensing

Edmund Optics Inc.

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• transmit UV, visible, NIR
• beam deviation down to 3 arcsec
• surface accuracy λ/8

In laser applications such as remote sensing, long-path-length metrology and velocimetry, the alignment procedure can be time-consuming. Corner cube retroreflectors have advantages over mirrors in this situation because they reflect the beam precisely back along its original path. Edmund Optics has introduced UV fused-silica corner cube retroreflectors with low temperature sensitivity.

The fused silica provides high transmittance of ultraviolet, visible and near-infrared wavelengths. Its coefficient of thermal expansion is 0.5 μm/°C. The corner cube retroreflector, also known as a trihedral prism, diverts the beam via three total internal reflections so that it emerges to retrace its incoming path, independent of the incoming angle. In contrast, a plane mirror does this at only one angle of incidence, when the ray strikes it at 90° to its surface. This property saves time in applications requiring precise alignment of the laser beam.

The UV corner cubes are available in four sizes with diameters of 7.16, 12.70, 25.40 and 50.80 mm, with tolerance of 0/–0.10 mm, and the largest cubes have a beam deviation of only 3 arcsec. The height tolerance of most of the cubes is ±0.25 mm. They can be supplied with aluminium coating to reflect more light, or without the coating. The retroreflectors expand the existing range of corner cubes, which are made from BK7 optical glass with a surface accuracy of λ/8 and are available in sizes up to 76.2 mm. The surface accuracy of the UV-grade fused-silica cubes exceeds that of the BK7 products, making them suitable for laser applications.

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Published: June 2008