Calcium Fluoride Plano-Concave Lenses, Uncoated

Overview
Graphs
Focal Length Shift
Mounting Options
Feedback

Common Specifications
Substrate Material	Vacuum-Grade Calcium Fluoride^a
Wavelength Range (Uncoated)^b	0.18 - 8.0 μm
Diameters Available	1/2" or 1"
Diameter Tolerance	+0.00/-0.10 mm
Thickness Tolerance	±0.1 mm
Focal Length Tolerance	±1%
Surface Quality	40-20 (Scratch-Dig)
Surface Flatness (Plano Side)	λ/2
Spherical Surface Power (Concave Side)^c	3λ/2
Surface Irregularity (Peak to Valley)	λ/2
Centration	≤3 arcmin
Clear Aperture	>90% of Diameter
Design Wavelength	588 nm

Click Link for Detailed Specifications on the Substrate
These lenses are also available with an AR coating for the 2 - 5 µm range.
Much like surface flatness for flat optics, spherical surface power is a measure of the deviation between the surface of the curved optic and a calibrated reference gauge, typically for a 633 nm source, unless otherwise stated. This specification is also commonly referred to as surface fit.

Zemax Files
Click on the red Document icon next to the item numbers below to access the Zemax file download. Our entire Zemax Catalog is also available.

Features

Uncoated Vacuum-Grade Calcium Fluoride Substrate
Ø1/2" and Ø1" Versions Available
Focal Lengths from -18.0 mm to -500.0 mm

Thorlabs' Ø1/2" and Ø1" Calcium Fluoride (CaF₂) Plano-Concave Lenses offer high transmission from 0.18 µm to 8.0 μm. CaF₂ is commonly used for applications requiring high transmission in the infrared and ultraviolet spectral ranges. Its extremely high laser damage threshold makes it useful for use with excimer lasers. The material exhibits a low refractive index, varying from 1.35 to 1.51 within its usage range of 180 nm to 8.0 μm. Calcium fluoride is also fairly chemically inert and offers superior hardness compared to its barium fluoride, magnesium fluoride, and lithium fluoride cousins.

Like all plano-concave lenses, these lenses have negative focal lengths and can be used to diverge collimated beams; in this case, the curved surface should face the source in order to minimize spherical aberration. In addition, they can be employed to offset the effects of spherical aberration caused by other lenses in an optical system.

Selection Guide

Calcium Fluoride Lenses

Other MIR Lenses

Other Spherical Singlets

Click to Enlarge
Click Here for Raw Data

Total Transmission of Optic (CaF₂ Substrate, Uncoated)

The table below gives the approximate theoretical transmission of these uncoated optics for a few select wavelengths in the 0.18 - 8.0 μm range. To see an excel file that lists all measured transmission values for this wavelength range, please click here.

Wavelength (μm)	Total Transmission
0.2	0.910
0.4	0.929
0.6	0.935
0.8	0.937
1.0	0.938
1.2	0.938
1.4	0.938
1.6	0.938
1.8	0.939
2.0	0.939

Wavelength (μm)	Total Transmission
2.2	0.939
2.4	0.939
2.6	0.940
2.8	0.940
3.0	0.940
3.2	0.941
3.4	0.941
3.6	0.941
3.8	0.942
4.0	0.942

Wavelength (μm)	Total Transmission
4.2	0.943
4.4	0.943
4.6	0.943
4.8	0.944
5.0	0.945
5.2	0.945
5.4	0.945
5.6	0.946
5.8	0.946
6.0	0.947

Wavelength (μm)	Total Transmission
6.2	0.947
6.4	0.947
6.6	0.948
6.8	0.949
7.0	0.949
7.2	0.948
7.4	0.947
7.6	0.946
7.8	0.945
8.0	0.944

Wavelength-Dependent Focal Length Shift

The paraxial focal length of a lens is wavelength dependent. The focal length listed below for a given lens corresponds to the value at the design wavelength (i.e., the focal length at 588 nm). Since CaF₂ offers high transmission from 0.18 - 8.0 µm, users may wish to use these lenses at other popular wavelengths. Click on the icons below to view theoretically-calculated focal length shifts for wavelengths within the 0.18 - 8.0 µm range.

Ø1/2" Plano-Concave Lenses

Item #	LC5919	LC5749
Focal Length @ 588 nm	-18.0 mm	-25.0 mm
Focal Length Shift (Click for Details)
Raw Data (Click to Download)	Data	Data

Ø1" Plano-Concave Lenses

Item #	LC5269	LC5401	LC5289	LC5952	LC5893
Focal Length @ 588 nm	-40.0 mm	-75.0 mm	-100.0 mm	-200.0 mm	-500.0 mm
Focal Length Shift (Click for Details)
Raw Data (Click to Download)	Data	Data	Data	Data	Data

Click to Enlarge
CXY1 Translation Mount and
SM1 Lens Tube Mounted in a
30 mm Cage System

Click to Enlarge
Ø1" Optic Mounted in a
ST1XY-S XY Translator

Click to Enlarge
LMR1 Fixed Mount with Ø1" Lens

Click to Enlarge
LM2XY Translating Mount with Ø2" Lens

Recommended Mounting Options for Thorlabs Lenses
Item #		Mounts for Ø2 mm to Ø10 mm Optics
Imperial	Metric	Mounts for Ø2 mm to Ø10 mm Optics
(Various)		Fixed Lens Mounts and Mini-Series Fixed Lens Mounts for Small Optics, Ø5 mm to Ø10 mm
(Various)		Small Optic Adapters for Use with Standard Fixed Lens Mounts, Ø2 mm to Ø10 mm
Item #		Mounts for Ø1/2" (Ø12.7 mm) Optics
Imperial	Metric	Mounts for Ø1/2" (Ø12.7 mm) Optics
LMR05	LMR05/M	Fixed Lens Mount for Ø1/2" Optics
MLH05	MLH05/M	Mini-Series Fixed Lens Mount for Ø1/2" Optics
LM05XY	LM05XY/M	Translating Lens Mount for Ø1/2" Optics
SCP05		16 mm Cage System, XY Translation Mount for Ø1/2" Optics
(Various)		Ø1/2" Lens Tubes, Optional SM05RRC Retaining Ring for High-Curvature Lenses (See Below)
Item #		Mounts for Ø1" (Ø25.4 mm) Optics
Imperial	Metric	Mounts for Ø1" (Ø25.4 mm) Optics
LMR1	LMR1/M	Fixed Lens Mount for Ø1" Optics
LM1XY	LM1XY/M	Translating Lens Mount for Ø1" Optics
ST1XY-S	ST1XY-S/M	Translating Lens Mount with Micrometer Drives (Other Drives Available)
CXY1		30 mm Cage System, XY Translation Mount for Ø1" Optics
(Various)		Ø1" Lens Tubes, Optional SM1RRC Retaining Ring for High-Curvature Lenses (See Below)
Item #		Mount for Ø1.5" Optics
Imperial	Metric	Mount for Ø1.5" Optics
LMR1.5	LMR1.5/M	Fixed Lens Mount for Ø1.5" Optics
(Various)		Ø1.5" Lens Tubes, Optional SM1.5RR Retaining Ring for Ø1.5" Lens Tubes and Mounts
Item #		Mounts for Ø2" (Ø50.8 mm) Optics
Imperial	Metric	Mounts for Ø2" (Ø50.8 mm) Optics
LMR2	LMR2/M	Fixed Lens Mount for Ø2" Optics
LM2XY	LM2XY/M	Translating Lens Mount for Ø2" Optics
CXY2		60 mm Cage System, XY Translation Mount for Ø2" Optics
(Various)		Ø2" Lens Tubes, Optional SM2RRC Retaining Ring for High-Curvature Lenses (See Below)
Item #		Adjustable Optic Mounts
Imperial	Metric	Adjustable Optic Mounts
LH1	LH1/M	Adjustable Mount for Ø0.28" (Ø7.1 mm) to Ø1.80" (Ø45.7 mm) Optics
LH2	LH2/M	Adjustable Mount for Ø0.77" (Ø19.6 mm) to Ø2.28" (Ø57.9 mm) Optics
VG100	VG100/M	Adjustable Clamp for Ø0.5" (Ø13 mm) to Ø3.5" (Ø89 mm) Optics
SCL03	SCL03/M	Self-Centering Mount for Ø0.15" (Ø3.8 mm) to Ø1.77" (Ø45.0 mm) Optics
SCL04	SCL04/M	Self-Centering Mount for Ø0.15" (Ø3.8 mm) to Ø3.00" (Ø76.2 mm) Optics
LH160C	LH160C/M	Adjustable Mount for 60 mm Cage Systems, Ø0.50" (Ø13 mm) to Ø2.00" (Ø50.8 mm) Optics
SCL60C	SCL60C/M	Self-Centering Mount for 60 mm Cage Systems, Ø0.15" (Ø3.8 mm) to Ø1.77" (Ø45.0 mm) Optics

Mounting High-Curvature Optics

Thorlabs' retaining rings are used to secure unmounted optics within lens tubes or optic mounts. These rings are secured in position using a compatible spanner wrench. For flat or low-curvature optics, standard retaining rings manufactured from anodized aluminum are available from Ø5 mm to Ø4". For high-curvature optics, extra-thick retaining rings are available in Ø1/2", Ø1", and Ø2" sizes.

Extra-thick retaining rings offer several features that aid in mounting high-curvature optics such as aspheric lenses, short-focal-length plano-convex lenses, and condenser lenses. As shown in the animation to the right, the guide flange of the spanner wrench will collide with the surface of high-curvature lenses when using a standard retaining ring, potentially scratching the optic. This contact also creates a gap between the spanner wrench and retaining ring, preventing the ring from tightening correctly. Extra-thick retaining rings provide the necessary clearance for the spanner wrench to secure the lens without coming into contact with the optic surface.

Posted Comments:

user (posted 2020-06-01 15:56:45.51)

Dear Sir/Madam Is it possible to make CaF2 Plano-Concave Lenses with UV anti-reflective coating? How much it will cost? Best regards, Pawel

YLohia (posted 2020-06-02 09:10:32.0)

Hello Pawel, thank you for contacting Thorlabs. Custom lenses and coatings can be requested by emailing your local Thorlabs Tech Support team (techsupport.se@thorlabs.com). We will reach out to you directly.

matsuura (posted 2016-07-06 17:38:13.217)

Laser beam size：2.0mm－φ2.5mm Pules energy:＞100μJ Pules Wide:＞50ps Wavelength :266nm Can use this Products?

tcohen (posted 2012-03-08 14:40:00.0)

Response from Tim at Thorlabs: Thank you for your feedback. CaF2 has very low birefringence and CaF2 lenses are typically cut in a way to minimize it. I am looking into the exact orientation and will update you with the information as soon as I have it.

cfho (posted 2012-03-07 05:16:39.0)

Dear sir Do you have the information about the crystal orientation of caf2 lens reference to the optical axis thank you very much Best regards, ho cheng-fang

Ø1/2" CaF₂ Plano-Concave Lenses, Uncoated

Item #	Diameter	Focal Length	Diopter^a	Radius of Curvature	Center Thickness	Edge Thickness^b	Back Focal Length^c	Reference Drawing
LC5919^d	1/2" (12.7 mm)	-18.0 mm	-55.6	-7.8 mm	2.0 mm	5.3 mm	-19.4 mm
LC5749^e	1/2" (12.7 mm)	-25.0 mm	-40.0	-10.9 mm	2.5 mm	4.6 mm	-26.7 mm

Reciprocal of the Focal Length in Meters
Edge Thickness Given Before 0.2 mm at 45° Typical Chamfer
Measured at the Design Wavelength, 588 nm
Suggested Fixed Lens Mounts: LMR05(/M) & SM05L03
Suggested Fixed Lens Mount: LMR05(/M)

Ø1" CaF₂ Plano-Concave Lenses, Uncoated

Item #	Diameter	Focal Length	Diopter^a	Radius of Curvature	Center Thickness	Edge Thickness^b	Back Focal Length^c
LC5269^d	1" (25.4 mm)	-40.0 mm	-25.0	-17.4 mm	2.0 mm	7.3 mm	-41.4 mm
LC5401^e	1" (25.4 mm)	-75.0 mm	-13.3	-32.5 mm	2.5 mm	5.1 mm	-76.7 mm
LC5289^e	1" (25.4 mm)	-100.0 mm	-10.0	-43.4 mm	3.0 mm	4.8 mm	-102.1 mm
LC5952^e	1" (25.4 mm)	-200.0 mm	-5.0	-86.8 mm	3.5 mm	4.5 mm	-202.4 mm
LC5893^e	1" (25.4 mm)	-500.0 mm	-2.0	-216.9 mm	4.0 mm	4.5 mm	-502.8 mm

Reciprocal of the Focal Length in Meters
Edge Thickness Given Before 0.2 mm at 45° Typical Chamfer
Measured at the Design Wavelength, 588 nm
Suggested Fixed Lens Mounts: LMR1(/M) & SM1L05
Suggested Fixed Lens Mount: LMR1(/M)

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