Calomel Infrared Polarisers

16 Feb 2023

Calomel Infrared Polarisers are the latest products added to Knight Optical’s vast catalogue. Calomel is a crystalline material which transmits from visible to far infrared with a very strong birefringence, almost four times higher than calcite.

There are many benefits of this material for polarising optics including:

• Long transmission range from 0.38µm to 17µm.
• Strong birefringence of Δn=0.683.
• Optically positive, n_e > n_o.
• High extinction ratio (ER) between 2.5 to 17µm, ER > 1:15000.
• Suitable for high-power CW lasers.
• High figure of merit, M2, for acousto-optical devices.

This transmission range into the LWIR thermal waveband means it can be used in applications such as astronomy, spectroscopy, and laser instrumentation. Calomel polarisers are a good alternative to an IR wire grid polariser.

Our stock Calomel Infrared Polarisers consist of a Glan-Foucault type and a Wollaston type, both with 10x10mm apertures. These are mounted in 360° rotational mounts for better handling and alignment.

The Wollaston polariser has two orthogonally polarised outputs (e-ray and o-ray) with a separation angle of 14°. 

The Glan-Foucault polariser transmits the positively polarised o-ray. 

Below are the tolerances for both the Glan-Foucault and Wollaston polarisers:

Dimension tolerance: ± 0.20 mm

Flatness: < 0.3λ

Surface Quality: < 40-20 scratch/dig

Custom Calomel optical components can also be produced, including different variations of the Glan-Foucault and Wollaston polarisers we have in stock, including a larger 15x15mm aperture, or the addition of an AR coating either between 3-5µm or 8-10µm. Other optics include:

• Depolarisers
• Windows
• Wedges
• Prisms
• Plates

Utilising our metrology facilities, Knight Optical ensures that the optical components that leave our premises are to specification, including visual inspection in our quality department prior to shipment.

Read more on calomel infrared polarisers in our dedicated blog.

Contact our technical account managers with your enquiries.