Dichroic Mirrors

Dichroic mirrors are used to combine beams or to split two beams that have different wavelengths.

With a long-pass mirror, the long wavelengths are transmitted while the short ones are reflected. Short-pass mirrors allow the short wavelengths to pass and reflect the long ones.

On request, we also develop complex coating designs with multiple transmission and reflection ranges. Such optics are used e.g. in modern laser material processing, where the working plane is observed in different spectral ranges.

Follow these “golden rules” to find the best mirror design for your application:

• Bandwidth:
  The bandwidth for the reflected part of the beam is limited. For the best possible beam separation or combination, it is important to allow a wavelength range to be transmitted and individual wavelengths to be reflected.
  Examples: HR1064HT400-700;HR355HT532+1064
   
• Polarization:
  The absolute degree of reflection is higher for s-polarized light than it is for p-polarized light. The opposite relation applies for transmissions. Therefore, keep the polarizations in mind when planning your assembly.
   
• Reflection better than transmission:
  The efficiency is higher for the reflected beam. If your application requires high efficiency at a certain wavelength, you should take this into account when selecting the mirror.
   
• Beam combination of SHG, THG, ...:
  Reflection peaks occur at λ/2, λ/3, etc. of the reflected wavelength. In this case, you should prefer a long-pass coating - i.e. an HR355HT532+1064 coating rather than an HR1064+532HT355 coating.