Specac - Holographic IR Wire Grid Polarizers

We have four main product types:

• FTIR accessory polarizers (GS12000-series) - these fit to the aperture ports on certain Specac FTIR accessories.
• "Opto-Physics" polarizers (GS57500-series) - to fit standard 25 mm and 50 mm optical mounts.
• Standard IR polarizers, custom mounted - can be ordered as unmounted 25 mm optics or in 41, 55, 70, or 90 mm mounts.
• High extinction IR polarizers - as above, but with increased grid specification for top performance.

The manufacturing process involves exposing a photo-resist coating on a suitable material substrate to an interferometrically-generated fringe pattern from a monochromatic UV source. The regular sinusoidal profile of the developed photo-resist is subsequently metal-coated at an oblique angle to create an array of fine parallel lines at a set period. This technique lends itself well to the generation of extremely uniform submicron grid wire spacings (an option of 2500 or 4000 lines per mm), which have a significantly reduced level of light scattering in comparison to traditional ruled wire grid polarizers. As the wire grid is formed on the photo-resist itself, the technique is also well suited to fabricating polarizers on substrates that do not otherwise lend themselves to the ruling process. The Standard Infrared Polarizers that are provided as part of the GS57010 Series range of polarizers available from Specac consist of a specific substrate material that has a polarized grid photo-etched onto one surface of the circular substrate material. Each polarizer substrate option has a polarizing grid of 4000 lines per mm onto a substrate of varying diameters and thickness. The choice of substrate materials are:

• KRS-5 – spectral transmission range 2 – 35 µm
• Germanium – spectral transmission range 8 – 12 µm
• CaF₂ – spectral transmission range 1 – 10 µm
• BaF₂ – spectral transmission range 1 – 12.5 µm
• ZnSe – spectral transmission range 1 – 1 5µm

  The GS57010 Series polarizers are also offered in as High Extinction Ratio (HER) and Image Quality (IQ) Infrared polarizers. For HER Infrared polarizers, these are offered in the same way as the Standard Infrared polarizer for substrates and support ring mount size options, but they are manufactured at 4000 lines per mm with an enhanced coating process that ensures a higher level of polarization extinction without jeopardizing transmission throughput. For IQ Infrared polarizers, these are offered in the same way as the Standard Infrared polarizer from the choice of support ring mount size options, but only as Germanium and ZnSe substrate materials. They are manufactured at 4000 lines per mm with specific anti-reflection coatingsand a high specification of optical flatness and parallelism, which make these polarizers very well suited for imaging applications. Typical applications:

• Infrared spectroscopy of materials (typically plastics/polymer analysis and crystallography)
• Infrared microscopy (sample characterization)
• IR Ellipsometry/Reflectometry
• NIR/Mid-IR thermal imaging systems
• Plasma diagnostics
• Beam splitters in polarized light interferometry
• Analysis in infrared astronomy
• Low power laser polarization and beam attenuation
• Coupling devices for Mid-IR and long-wavelength lasers

• (Polarizers) AN21-02: How polarized radiation helps in studies of the properties of functional materials