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Reflective optics for Non-Visible Lasers

Beam Conditioning Optics for UV, IR, and Broadband Lasers


Conventional glass beam expanders are highly wavelength dependent


Reflective optics are advantageous for UV, IR, broadband, and ultrafast lasers


Reflective beam shaping optics are achromatic, decreasing aberrations


Well-positioned for emerging laser technologies due to flexibility

UV, IR, broadband, and ultrafast lasers are essential to an enormous range of applications from spectroscopy to micromachining to laser surgery. However, it is more difficult to find beam shaping optics such as beam expanders for these non-visible lasers, as conventional transmissive optics are highly wavelength dependent and can suffer from dispersion. Reflective beam shaping optics solve these issues with a broadband achromatic design by completely eliminating chromatic and spherical aberration. Reflective beam expanders and mirrors also tend to be less expensive than those specially designed for a specific non-visible wavelength or broad waveband.

Reflective Beam Expanders

Reflective Beam Expanders are modified Gregorian or Cassegrain mirror systems that offer broadband performance virtually free of chromatic and spherical aberration. They are compatible with a wide range of laser sources including:

  • UV Lasers (Excimer, Nd:YAG, etc.)
  • Infrared Lasers (Nd:YAG, CO2, Quantum Cascade, etc.)
  • Ultrafast Lasers (Ti:Sapphire, Fiber, etc.)
  • Tunable Lasers (Ti:Sapphire, Dye, Quantum Cascade, etc.)

A convex mirror is used to expand an incident beam onto a concave mirror, resulting in a larger collimated beam.

The curved mirrors of a Monolithic Reflective Beam Expander expand the incident laser beam<
Figure 1: The curved mirrors of a Monolithic Reflective Beam Expander expand the incident laser beam

Focusing Mirrors

Focusing mirrors, such as Off-Axis Parabolic Mirrors (OAPs), also eliminate chromatic aberrations and avoid the drawbacks of transmissive beam conditioning optics. Parabolic mirrors have the added benefit of focusing or collimating light without introducing spherical aberration. OAPs are side sections of a larger parent parabolic mirror, giving them more interactive space around the focal point without disrupting the beam, as seen in Figure 2.

Diagrams of 15° and 45° OAP mirrors
Figure 2: Diagrams of 15° and 45° OAP mirrors

UV Lasers

Ultraviolet (UV) lasers are ideal for many applications including laser micromachining, medical lasers, semiconductor processing, and fluorescence microscopy. Many laser optics applications are utilizing short UV wavelengths in order to create very small and precise features with minimal peripheral heating. UV lasers also offer higher spatial resolution than visible or IR lasers because the laser spot size is directly proportional to wavelength.

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Size Comparison of an Ultra-Compact Microscope Objective with a Standard Microscope Objective

2μm Lasers

The unique absorption characteristics of 2μm lasers allow them to create very small and precise cuts in biological tissue and plastics with minimal localized heating. These absorption characteristics give 2μm lasers an advantage over 1µm lasers for certain applications. 2µm lasers are ideal for highly precise applications including medical surgery and plastic processing.

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Size Comparison of an Ultra-Compact Microscope Objective with a Standard Microscope Objective

Ultrafast Lasers

Ultrafast lasers are mode-locked lasers that are capable of emitting extremely short pulses with durations of femtoseconds or picoseconds and high peak powers. Because of the Fourier limit (also known as energy-time uncertainty), pulses with such short temporal length have a wide wavelength spectrum spread over a considerable bandwidth. This can lead to severe chromatic aberrations in transmissive optics, but reflective beam shaping optics can be used with ultrafast lasers with virtually no chromatic aberration.

Size Comparison of an Ultra-Compact Microscope Objective with a Standard Microscope Objective

Reflective Beam Conditioning Optics at Edmund Optics®

TECHSPEC Monolithic Reflective Beam Expanders (Mark I)

Monolithic Reflective Beam Expanders

The diamond turned TECHSPEC® Monolithic Reflective Beam Expanders are ideal for broadband or achromatic beam expansion and a wide range of light sources. They have minimal wavefront distortion and their achromatic, all-reflective design enables them to be used with tunable, ultraviolet, and ultrafast lasers. Integrated mounting features including reflective flats, thread holes, and thru-holes greatly simplify mounting, alignment, and integration into any laser-based application. The monolithic construction also ensures stability and performance independent of changes in temperature.

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Off-Axis Parabolic First Surface Metal Mirrors

Off-Axis Parabolic First Surface Metal Mirrors

TECHSPEC® Off-Axis Parabolic (OAP) Metal Mirrors offer surface roughness down to 50Å RMS and are free of chromatic and spherical aberration. Their solid metal design and lack of adhesives provides optimal thermal conductivity. OAPs allow for unrestricted access to the focal point, facilitating compact system designs. These features make OAPs ideal for instrumentation and laser systems including MTF, FLIR, FTIR, and Schlieren, along with IR lasers such as quantum cascade lasers. TECHSPEC® diamond turned metal substrate mirrors are available in 15°, 30°, 45°, 60°, or 90° Off-Axis options.

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FAQ  What magnifications are available for the TECHSPEC® Canopus Reflective Beam Expanders?
The TECHSPEC® Canopus Reflective Beam Expanders are available with magnifications of 2X, 3X, and 5X.
FAQ  What coating options are available for the TECHSPEC® Canopus Reflective Beam Expanders?

The TECHSPEC® Canopus Reflective Beam Expanders are available with enhanced aluminum, protected aluminum, and bare gold coatings.

FAQ  What wavelength range do TECHSPEC® Off-Axis Parabolic Mirrors cover?

The wavelength range for TECHSPEC® Off-Axis Parabolic Mirrors is dependent on the mirror’s coating. Three different coatings are available including protected aluminum, protected gold, and bare gold, covering 400nm to more than 12000nm.

FAQ   What design parameters should I use for a custom Off-Axis Parabolic Mirror?

The design parameters required to make a cost efficient, custom OAP include the reflected focal length, reflected angle, the tolerance for the focal point, and the reflected wavefront distortion.


Application Notes

Technical information and application examples including theoretical explanations, equations, graphical illustrations, and much more.

UV Optics: Tighter Tolerances and Different Materials

Roughness of Diamond Turned Off-Axis Parabolic Mirrors

Metallic Mirror Coatings

Off-Axis Parabolic Mirror Selection Guide

Related Pages

Additional webpages that describe related products, capabilities, or concepts.

Diamond Turning Capabilities

Laser Optics


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