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Achromatic Retarders

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Halbo Optics produce two ranges of achromatic retarder:

Magnesium fluoride/crystal quartz plate combinations  
Double Fresnel rhombs  

Magnesium Fluoride/Quartz Plates

Achromatic retardation plates can be realised by combining a thin plate of crystal quartz with one of magnesium fluoride. With their optic axes orthogonal, the spectral dispersion of birefringence in each plate cancels out over a defined spectral range. This results in a zero order achromatic wave plate. Halbo Optics manufacture both quarter and half wave achromatic retardation plates using this technique.

Standard achromatic retardation plates are air spaced and cover 3 principal bands:

400nm - 650nm  
500nm - 800nm  
600nm - 900nm  

Mounts

Achromatic plate retarders are supplied mounted in type 3 mount as standard. Mount thickness is 6mm.

Specifications

 Model # Spectral Range (nm) Retardation Aperture (mm) Peak Trans. (%) Max Peak Power (MW/cm2) Max CW Power (W/cm2) Mount Dia. (mm)
 Quarter Wave Achromatic Retardation Plates
 RPQHA10-400-650 400-650 Quarter 10 85 200 100 25.4
 RPQHA20-400-650 400-650 Quarter 20 85 200 100 31.8
 RPQHA10-500-800 500-800 Quarter 10 85 200 100 25.4
 RPQHA20-500-800 500-800 Quarter 20 85 200 100 31.8
 RPQHA10-600-900 600-900 Quarter 10 85 200 100 25.4
 RPQHA20-600-900 600-900 Quarter 20 85 200 100 31.8
 Half Wave Achromatic Retardation Plates
 RPHHA10-400-650 400-650 Half 10 85 200 100 25.4
 RPHHA20-400-650 400-650 Half 20 85 200 100 31.8
 RPHHA10-500-800 500-800 Half 10 85 200 100 25.4
 RPHHA20-500-800 500-800 Half 20 85 200 100 31.8
 RPHHA10-600-900 600-900 Half 10 85 200 100 25.4
 RPHHA20-600-900 600-900 Half 20 85 200 100 31.8

Achromatic Quarter Wave Retarder Performance

The performance of quarter wave retarders is shown below. Series RPHHA half wave plate retarders will have exactly twice the retardation shown for the RPQHA series.

Performance of achromatic quarter wave retarders

Double Fresnel Rhombs

Fresnel rhombs are manufactured from 3 materials:

BK7 optically contacted  
Fused silica optically contacted  
Calcium fluoride air spaced  

Specifications

 Material BK7 Silica CaF2
 Spectral Range (nm) 365-800 230-700 190-900
 Peak Transmission (%) 92 92 85
 Max Peak Power (MW/cm2) 200 200 20
 Max CW Power (W/cm2) 100 100 10
 Deviation (min) <1 <1 <1

Double Fresnel rhombs are described in more detail in Fresnel Rhombs.

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