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Custom KRS5

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Knight Optical offers high-quality KRS-5 windows and optical components, using the unique properties of KRS5 (Thallium Bromo-Iodide). This material is renowned for its excellent transmission capabilities in the deep infrared range, making it a preferred choice for spectroscopic and other IR applications.

Our KRS5 glass is created to meet diverse optical needs, ensuring excellent performance in environments requiring precise infrared transmission.

We understand the importance of material quality and optical precision. Our KRS-5 windows are available in various dimensions and can be custom-made to fit your specific requirements. Additionally, the KRS-5 refractive index is thoroughly considered in the design of each component, ensuring optimal performance in your optical systems.

For applications requiring unique specifications, we offer custom solutions, including Thallium Bromo-Iodide components, specifically for your exact needs. Whether you need anti-reflective coatings or specific geometric configurations, our team can provide KRS5 glass and KRS-5 crystal components that meet your project’s demands.

Speak to our experts about your Custom KRS-5 needs today

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    Optical Properties of KRS5

    Leveraging our extensive experience and state-of-the-art metrology lab, we ensure that each KRS-5 window and optical component meets Knight Optical’s high standards for quality and performance. Our commitment to excellence and customer satisfaction makes us an excellent provider in the optical industry, ready to support your projects with precision-made KRS5 and Thallium Bromoiodide components.

    Discover how our KRS-5 optical components can enhance your optical systems by contacting our expert team today. Below is a brief summary of KRS5’s optical properties, a full data sheet is available here.


    Transmission Range0.6 to 40µm
    Refractive Index2.371 @ 10µm
    Density7.371 g/cm3
    Melting Point414.5°C
    HardnessKnoop 40.2
    Diameter< 5mm to 50mm
    Form error (@633nm)< 0.25 waves
    Centration/parallelism< 1 arc minute
    Scratch/dig< 40/20
    Typical coatingsBBAR @ 2-40µm, DLC @ 2-40µm

    Frequently Asked Questions

    KRS5, also known as Thallium Bromo-Iodide, is widely used in infrared and multispectral applications due to its high refractive index and broad transmission range. It is particularly useful in IR spectroscopy, thermal imaging, and other IR applications due to its excellent transmission properties from the visible wavelengths up to the far-infrared range.

    A KRS5 crystal is known for its high refractive index and wide transmission range, which makes it suitable for infrared and multispectral system components. Additionally, KRS5 is non-hygroscopic, making it stable and usable in various environmental conditions without degradation.

    Yes, KRS5 windows can be used in high moisture environments as KRS5, or Thallium Bromo-Iodide, is non-hygroscopic. This means it does not absorb water easily, making it ideal for applications where moisture is present.

    KRS5 glass stands out due to its wide infrared transmission range and high refractive index. Unlike other infrared materials, KRS5 can transmit infrared light up to far-infrared wavelengths, making it highly valuable for a broad range of IR applications.

    The KRS-5 refractive index is significantly high, which is crucial as it affects the bending of light passing through the material. This property makes KRS5 particularly suitable for high-performance infrared optics where precise light manipulation is necessary.

    Thallium Bromo-Iodide, or KRS5, performs exceptionally well compared to other IR materials due to its extensive transmission range and ability to operate effectively across a wide range of temperatures and environmental conditions. This makes it a preferred choice for challenging infrared applications where high optical performance is required.

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    We are ready and waiting to answer any queries you may have about germanium.

    Additional Information

    High Chemical Resistance

    KRS5 is non-hygroscopic with a high chemical resistance against strong acids. It is manufactured by the sealed-ampoule Stockbarger technique, with a high-purity starting material to remove the possibility of absorption bands in the mid-IR region.

    Cold Flow

    KRS5 also tends to cold flow, meaning it slowly deforms in shape under mechanical stress and pressure.


    Health and Safety

    KRS5 is toxic and must be handled with extreme care. Gloves should be worn, and hands washed thoroughly after handling the optics.

    Typical Applications

    Germanium for Fourier Transform Infrared Spectroscopy (FTIR)

    Fourier Transform Infrared Spectroscopy (FTIR)

    KRS5 is widely used as a substrate for ATR prisms due to its wide transmission band, low absorption, and high refractive index. It is also stable under normal atmospheric conditions. KRS5 is also used as transmission windows for liquid and gas samples.

    Wire Grid IR Polarisers

    Thallium Bromo-iodide is used as a substrate for wire grid IR polarisers. The grooves on the polarisers are manufactured using a holographic technique which can create submicron wire grid spacing. The grooves are filled with a metal deposit to create the wire grid. Wire grid IR polarisers polarise light from an unpolarised IR laser source, and attenuate light from a polarised source. These polarisers are used in a variety of applications including FTIR spectroscopy, medical imaging, and aerospace.

    Infrared Lenses for FLIR Thermal Imaging

    Athermalised imaging systems

    KRS5 can be used in conjunction with germanium to correct for thermal defocusing within a system. It will often be used as a triplet along with another infrared material, such as zinc sulphide, to correct for the chromatic aberration that KRS5 can introduce.

    Get in touch with us:

    With our in-house state-of-the-art metrology laboratory you can be confident that your optical components will meet your requirements. You can find out more about our testing facilities here.

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