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Warning: Calcite is a temperature-sensitive crystal and will crack if it is exposed to thermal shock. Allow the shipping packaging to reach complete thermal equilibrium before opening (6 - 8 hours).
Thorlabs' unmounted Glan-Thompson calcite polarizers offer the widest field of view of the calcite polarizers while maintaining a high extinction ratio. These unmounted prisms are ideal for custom applications; versions mounted in a round aluminum housing are also available. The GTH5 polarizers have a 5 mm x 5 mm aperture, while the GTH10 polarizers have a 10 mm x 10 mm aperture.
Both uncoated and coated polarizers are available. The uncoated polarizers are designed for use in the 350 nm to 2.3 μm range, while coated versions are available for the 350 - 700 nm or 650 -1050 nm range. Please see the Graphs tab for coating reflectivity data.
Glan-Thompson polarizers consist of two cemented prisms made from the highest optical grade calcite. Unpolarized light enters the polarizer, then is split at the intersection of the two crystals allowing s-polarized (e-ray) light to continue and p-polarized light (o-ray) to be reflected as shown in the diagram above. Due to the large field of view, these polarizers can be used for highly converging or diverging beams.
Note: As with all Glan-Thompson polarizers, the maximum optical intensity is limited by the cemented prism interface. For high-power applications, Thorlabs offers Glan Laser polarizers, which can handle power densities up to 500 W/cm2 (CW).
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The transmission graph above shows the typical transmission of an uncoated GTH10 Glan-Thompson Calcite Polarizer, including any internal losses. The transmission is valid for linearly polarized light aligned with the mark on the housing of the polarizer. Calcite is a natural material, and thus transmission can vary significantly, particularly in the UV and IR. Consequently, the performance data shown above may vary from lot to lot and is not guaranteed.
Polarization-Dependent Refraction - Glan-Thompson Calcite Polarizer
Our calcite polarizers are all based on high-grade, birefringent calcite crystals. Due to the birefringent nature of calcite, waves polarized in the direction of the optical axis propagate with a different index of refraction than waves polarized orthogonally to the optical axis. In our mounted Glan-Thompson polarizers, this birefringence causes the selective reflection and absorption of one polarization state of an incident beam and the transmission of the other orthogonal polarization state. When unpolarized light is incident on the optic, extraordinary rays pass straight through the polarizer while ordinary rays are reflected at an angle that depends on the light's wavelength and the length of the polarizer. The reflected ordinary rays are then scattered and partially absorbed by the optic's housing, resulting in a highly polarized output.
A calcite polarizer can be designed as either a polarization splitter/combiner or as a polarizer element that removes the angled, orthogonally polarized component of a beam. Our calcite polarizers are typically built out of two prisms, as shown in the drawing to the right. Since calcite is a soft crystal that is easily damaged, almost all of our calcite polarizers are offered in metal housings. With convenient threadings and adapters, these housings can easily be mounted into our opto-mechanical products.
Field of View
Calcite polarizers feature a field of view (FOV) that varies with both wavelength and entrance orientation. The FOV of these prisms must be considered during alignment and collimation procedures.
The side that absorbs the ordinary ray has an FOV that decreases as the wavelength increases (FOV 1). The opposite side has an FOV that increases as the wavelength increases (FOV 2). The FOV of Glan-Thompson polarizers is typically greater than the FOV of Glan-Taylor polarizers.
Calcite Polarizer Field of View (FOV)
Thorlabs uses only the highest quality natural calcite in our polarizing prisms. Typical transmission curves for these polarizers may be found on the Graphs tab. Because calcite is a naturally occuring material, variations in the crystal affect the transmission curve and the damage threshold rating. Variations in the calcite transmission curve are typically limited to wavelengths > 2 μm, making calcite an excellent material to use in the visible and NIR.
Polarizer Selection Guide
Thorlabs offers a diverse range of polarizers, including wire grid, film, calcite, alpha-BBO, rutile, and beamsplitting polarizers. Collectively, our line of wire grid polarizers offers coverage from the visible range to the beginning of the Far-IR range. Our nanoparticle linear film polarizers provide high thresholds for laser damage, up to 25 W/cm2, as well as extinction ratios as high as 100,000:1. Alternatively, our other film polarizers offer an affordable solution for polarizing light from the visible to the Near-IR. Next, our beamsplitting polarizers allow for use of the reflected beam, as well as the more completely polarized transmitted beam. Finally, our Alpha-BBO (UV), calcite (visible to Near-IR), and rutile (Near-IR to Mid-IR) polarizers each offer an exceptional extinction ratio of 100,000:1 within their respective wavelength ranges.
To explore the available types, wavelength ranges, extinction ratios, transmission, and available sizes for each polarizer category, click More [+] in the appropriate row below.