With special designed multi layer dielectric coating, the mirror reflect some wavelength and transmission other wavelength at the same time.
It can be used to splitter or conbine different wavelength.It can be also used in SHG laser system as Harmanic Separators.

 

Substrate can a precison window or a concave or cylindrical lens

Substrate Material: BK7 or Fused silica
Dimension: Dia.25.4 (+0/-0.2) x 6.3l5 (+/-0.2) mm (typically)
Flatness: L/4 commonly, L/10 for laser application
Surface quality: 20-10 (subatrate for laser application), 60-40 commonly
Parallelism: < 1 arc minute
Clear aperture: >85%
Protective chamfer
Front side dichroic coated
Back side AR coated for transmission wavelength

Coating example for Laser SHG 1064-->532nm application:
S1: HR R>99.5%@1064nm & HT T>90%@532nm, S2: AR R<0.25%@532nm, AOI=0deg.
S1: HR R>99.5%@532nm & HT T>90%@1064nm, S2: AR R<0.25%@1064nm, AOI=0deg.