TPX Plano-Convex Aspheric Terahertz Lenses


  • High Transparency from 0.1 to 3 THz
  • Available in Ø1", Ø50.0 mm, or Ø2"
  • Back Focal Lengths from 15.0 to 100.0 mm

AL235

Ø50.0 mm TPX Lens for THz,
f = 35.0 mm, NA = 0.54

Application Idea

AL235 Mounted in an LMR2

AL115

Ø1" TPX Lens for THz,
f = 15.0 mm, NA = 0.59

Related Items


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TPX and PTFE Attenuation Coefficients
Click to Enlarge

This graph compares the attenuation coefficients for TPX and PTFE materials as given by the Beer-Lambert law.
Optical Coatings Guide

Features

  • Material: TPX (Polymethylpentene)
  • Ideal for Use from 0.1 to 3 THz
  • Available Sizes: Ø1", Ø50.0 mm, and Ø2"
  • Back Focal Lengths Available from 15.0 to 100.0 mm

These TPX (Polymethylpentene) Aspheric Lenses are optimized for focusing or collimating THz radiation from 0.1 to 3 THz. These lenses offer higher transmission in this frequency region compared to our PTFE lenses. Please see the graph at the right for a comparison of the attenuation coefficients of these materials. TPX aspheric lenses are ideal for use with THz emission from our PCA800 THz Antenna and offer easier alignment and improved beam quality compared to off-axis parabolic mirrors.

Please note that it is essential to match the NA of the lens used for collimation with that of the output radiation to avoid truncating the spectrum, because the frequency of the emission from a THz antenna is angularly dependent. 

Common Specifications
Material TPX (Polymethylpentene)
Index of Refraction 1.45 at 1 THz
Shape Plano-Convex (Aspheric)
Optic Cleaning Tutorial
Aspheric Lens Design Variables
Click to Enlarge

Reference Drawing

Lens Design Formula

  • Positive Radius Indicates that the Vertex is Located Left of the Center
  • Negative Radius Indicates that the Vertex is Located Right of the Center
Variable Definitions
z Sag (Surface Profile) as a Function of Y
Y Radial Distance from Optical Axis
R Radius of Curvature
k Conic Constant

1

The radius of curvature and conic constant for each lens are listed in the tables below as well as in the individual lens drawings, which can be accessed by clicking the red docs icon () next to each lens sold below.


Posted Comments:
Jelle Dean  (posted 2024-09-17 13:16:38.157)
Hello, I'm interested in yours Plano-Convex Aspheric Terahertz Lenses, but I can't understand the way you defining BFL parameter. I'm really curious about the method you're using for calculating it. Is there an analytic equation or the presented BFLs are results of numerical/model simulation?
jpolaris  (posted 2024-09-27 06:29:35.0)
Thank you for contacting Thorlabs. The back focal length (BFL) is simply the distance from the rear surface of the lens (plano surface in the case of AL115) to the location of the tightest focus. This distance is verified through measurement, but it follows from Snell's law and the aspheric Sag (Z) equation. The index of the TPX substrate at 1 THz is 1.45. I have reached out to you directly to discuss further.
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Ø1" TPX Plano-Convex Aspheric Lenses

Item #a Diameter Back Focal Length Numerical Aperture Center Thickness Edge Thickness Clear Aperture Radius of Curvature (R)b Conic Constant (k)b
AL115 1" 15.0 mm 0.59 10.0 mm 2.5 mm 22.4 mm 9.9337 mm -0.57635
AL125 1" 25.0 mm 0.38 8.0 mm 3.1 mm 22.4 mm 13.878 mm -0.57699
AL150 1" 50.0 mm 0.21 7.0 mm 4.4 mm 22.4 mm 24.9368 mm -0.59181
  • Suggested Lens Mount: LMR1(/M)
  • Radius of Curvature and Conic Constant define the aspheric surface of the lens. Please see the Lens Equation tab above for details. 
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available
AL115 Support Documentation
AL115 Ø1" TPX Aspheric Lens for THz, Back Focal Length = 15.0 mm, NA = 0.59, Uncoated
$248.88
Today
AL125 Support Documentation
AL125 Ø1" TPX Aspheric Lens for THz, Back Focal Length = 25.0 mm, NA = 0.38, Uncoated
$248.88
Today
AL150 Support Documentation
AL150 Ø1" TPX Aspheric Lens for THz, Back Focal Length = 50.0 mm, NA = 0.21, Uncoated
$248.88
Today
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Ø50 mm TPX Plano-Convex Aspheric Lenses

Item #a Diameter Back Focal Length Numerical Aperture Center Thickness Edge Thickness Clear Aperture Radius of Curvature (R)b Conic Constant (k)b
AL235 50.0 mm 35.0 mm 0.54 18.0 mm 3.0 mm 47.0 mm 21.5277 mm -0.5805
  • Suggested Lens Mount: LMR2(/M)
  • Radius of Curvature and Conic Constant define the aspheric surface of the lens. Please see the Lens Equation tab above for details.
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available
AL235 Support Documentation
AL235 Ø50.0 mm TPX Aspheric Lens for THz, Back Focal Length = 35.0 mm, NA = 0.54, Uncoated
$446.76
Today
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Ø2" TPX Plano-Convex Aspheric Lenses

Item #a Diameter Back Focal Length Numerical Aperture Center Thickness Edge Thickness Clear Aperture Radius of Curvature (R)b Conic Constant (k)b
AL265 2" 65.0 mm 0.33 13.0 mm 4.1 mm 47.6 mm 33.657 mm -0.58018
AL2100 2" 100.0 mm 0.23 10.0 mm 4.0 mm 47.7 mm 48.6619 mm -0.5766
  • Suggested Lens Mount: LMR2(/M)
  • Radius of Curvature and Conic Constant define the aspheric surface of the lens. Please see the Lens Equation tab above for details.
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available
AL265 Support Documentation
AL265 Ø2" TPX Aspheric Lens for THz, Back Focal Length = 65.0 mm, NA = 0.33, Uncoated
$446.76
Today
AL2100 Support Documentation
AL2100 Ø2" TPX Aspheric Lens for THz, Back Focal Length = 100.0 mm, NA = 0.23, Uncoated
$446.76
Today