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Optical Surfaces has introduced small-diameter (25–60mm) reflective beam expanders, which are suitable for space-restricted applications such as high-power lasers and multi-wavelength interferometry.

Reflective beam expander

The company’s reflective beam expanders are aspheric mirror-based devices offering either beam expansion or reduction capabilities. Incorporating high-precision off-axis mirrors, the reflective beam expanders are said to provide an unobstructed output and highly efficient transmission.

By comparison, due to dispersion, lens-based beam expanders are only capable of compensating for focus at one wavelength of light, making them only suitable for expanding/reducing monochromatic sources.

Reflective beam expanders use mirrors that have constant focal lengths, regardless of the light being focused. Therefore, reflective beam expanders can be used with collimated polychromatic light without the need of any fine focus adjustment.

The off-axis design of these reflective beam expanders produces no central obscuration, and highly efficient transmission is obtained — unspoilt by spider diffraction patterns.

Key features and benefits

  • The small-diameter devices offer either beam expansion or reduction capabilities.
  • They are designed to be easy to use and provide accurate, unobstructed expansion/contraction of any collimated input light source.
  • They are available in standard (2.5x, 5x, 10x fixed magnification) or customer-specified (fixed or variable magnification) configurations.
  • They can be used without the need for internal re-alignment.
  • Each reflective beam expander is supplied housed in aluminium housing with provision for fixing to an optical table.
  • Alignment aids are provided to ensure correct beam pointing.
  • The devices are manufactured to better than lambda/5 surface accuracy.
  • An interferogram and OPD map is supplied with every reflective beam expander manufactured by Optical Surfaces.

Optical Surfaces

Optical Surfaces Ltd has been producing large and demanding high-precision optical components and systems for more than 40 years and is today internationally acknowledged for its technical expertise, attention to quality and customer service.

With the main workshops and test facilities deep underground in an area excavated from solid chalk, temperatures remain constant year-round and vibration is practically non-existent. These are important considerations when making, mounting and testing high-precision optics. Working with these natural advantages Optical Surfaces Ltd is able to supply high-precision off-axis parabolas, spherical and flat mirrors, etalons, aspherics, reference flats, windows, collimators and beam expanders for the most demanding applications. With such stable conditions, testing, particularly with long path lengths, becomes quantifiable and reliable. Investment in large-aperture Fizeau, Zygo GPI, Flashphase, Twyman Green, Scatterplate, and Laser Unequal Path interferometers allows detailed testing of the largest-diameter optics. Topographic and fringe analysis provides precise testing of surface roughness and confirms the wavefront of various surface forms. A rolling programme for calibration of test optics where possible to national standards and production approval to ISO 9001-2008 ensure that the quality of optics from Optical Surfaces is second to none.

Today the company is a trusted supplier to leading scientific, astronomical and defence establishments including many space projects worldwide.

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