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PTFE Plano-Convex Lenses
LAT115 Mounted in an LMR3
Click to Enlarge
This graph shows the attenuation coefficient of PTFE as given by the Beer-Lambert law.
We provide plastic plano-convex lenses made with Polytetrafluoroethylene (Virgin White PTFE), which has a low dielectric constant of approximately 1.96 at 520 GHz and an index of refraction of approximately 1.4. The f/#, inversely proportionate to the NA, is held relatively constant across the selection of lenses on the page. PTFE has a low dielectric constant, which ensures that the insertion loss is reasonably low. The typical operating range of PTFE is up to ~2 THz.
The Terahertz (THz) range can be expressed as the frequency range of 300 GHz to 10 THz or the wavelength range of 30 μm to 1 mm. Until recently, the THz range was a relatively unused part of the electromagnetic spectrum; however, in recent years the THz band has been gaining popularity in applications such as spectroscopy, astronomy, remote sensing, and in security (THz imaging). The THz band is situated between microwaves and optics on the electromagnetic spectrum. This location influences the mixture of microwave and optical technologies used in the THz band.
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.