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Fresnel Rhombs

Fresnel Rhombs

Fresnel rhombs generate a phase shift not by introducing an optical path difference but by employing the phase difference between the s-polarized and the p-polarized component in total internal reflection. This phase shift shows only minor spectral variation which makes the retarders suited for very broad spectral ranges.

We offer Fresnel rhombs made either from fused silica or from crown glass N-BK7. A retardation of λ/4 is achieved by two total internal reflections inside a single parallel epiped. The corresponding half wave retarders consist of two such epipeds which are connected by optical contact.

For the λ/2-rhombs we offer two types of holders. For the first version the rhombs are mounted to a plate. Both ends are equipped with cylindrical attachments for easy integration e.g. in rotation mounts. The second version is mounted on a post and includes a rotating part which is equipped with ball bearings and an angular graduation 0-360°. The λ/4-rhombs are delivered in a cylindrical holder.

Optical specifications

spectral range 215-450 nm 400-700 nm 500-1300 nm 650-1700 nm
material fused silica N-BK7 N-BK7 N-BK7
deviation of retardation ±5% ±1% ±1% ±1%
wavefront distortion <λ/4 <λ/4 <λ/4 <λ/4
prismatic deviation <2'' <2'' <2'' <2''
Strahlversatz (nur bei l/4) 12,6 mm 13,6 mm 13,4 mm 13,2 mm
reflectivity <1,7% (MgF2) <0,5% (BBAR) ~4% (unbeschichtet) ~4% (unbeschichtet)
temperature coefficient* a/R0(typ.) 15ž10-6/K 3ž10-6/K 3ž10-6/K 3ž10-6/K
tilt sensitivity* max. angle of incidence typ. 1° max. angle of incidence typ. 1° max. angle of incidence typ. 1° max. angle of incidence typ. 1°

* Definition ** Fresnel rhombs are quite sensitive to tilt and show a qualitative difference compared to birefringent retarders. Therefore, the angular coefficient is not meaningful for Fresnel rhombs.

Standard dimensions

version λ/2, plate mount λ/2, rotation mount λ/4
free aperture [mm] 9,5 9,5 9,5
mount diameter [mm] 50 59 48
mount length [mm] 65 76 40,3
connection [mm] 25 14 (post mount M8) 25
Art. No. 215-450 nm RFR 1.215 RFR 2.215 RFV 215
Art. No. 400-700 nm RFR 1.400 RFR 2.400 RFV 400
Art. No. 500-1300 nm RFR 1.500 RFR 2.500 RFV 500
Art. No. 650-1700 nm RFR 1.650 RFR 2.650 RFV 650

Wavelength dependence of the retardation

Fresnel Rhombs

Prices

order no. 1 piece in € 2 piece in € 3-5 piece in €
RFR 1.215 1448.- 1304.- 1140.-
RFR 1.400 1358.- 1224.- 1070.-
RFR 1.500 1358.- 1224.- 1070.-
RFR 1.650 1358.- 1224.- 1070.-

Prices

order no. 1 piece in € 2 piece in € 3-5 piece in €
RFR 2.215 2536.- 2344.- 2125.-
RFR 2.400 2463.- 2277.- 2063.-
RFR 2.500 2463.- 2277.- 2063.-
RFR 2.650 2463.- 2277.- 2063.-

Prices

order no. 1 piece in € 2 piece in € 3-5 piece in €
RFV 215 786.- 731.- 667.-
RFV 400 730.- 679.- 620.-
RFV 500 730.- 679.- 620.-
RFV 650 730.- 679.- 620.-
special antireflection coating on request
rhombs made from ZnSe for the mid IR range on request
unmount rhombs on request