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Custom Caesium Iodide

caesium iodide prisms

Bespoke Ordering Available

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Find out more about our custom caesium iodide

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Global leaders in custom optical solutions
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All optical components 100% QA checked
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Knight Optical are experts in providing custom caesium iodide solutions. Whether you’re looking for caesium iodide windows, caesium iodide lenses, or even caesium iodide scintillators, our bespoke service is designed to meet your exact specifications.

Understanding the critical role of caesium iodide in applications ranging from imaging to spectroscopy, we ensure that every piece, whether it’s lens, window, or another form, is crafted to the highest standards.

Caesium iodide (CsI) stands out as a versatile material that varies from UV to the Far IR spectrum, boasting the longest IR transmission among common infrared materials, reaching up to 55µm. This characteristic makes caesium iodide not just a component but an element in various optical applications. Its resilience against mechanical and thermal shocks makes caesium iodide a reliable choice; however, it’s vital to note that caesium iodide can degrade in certain conditions, particularly when exposed to moisture.

Our production capabilities are constantly evolving to match the demands of applications of caesium iodide. We’re always keen to push the boundaries to accommodate new challenges. If your project needs something not mentioned here, our technical sales team is ready to assist, ensuring that your custom caesium iodide components are perfectly aligned with your requirements.

caesium iodide prisms

Speak to our experts about your Custom Caesium Iodide needs today

Call +44 (0)1622 859444 Call +1 401 583 7846

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Dive into the forefront of optical solutions. Got questions about an optical product? Reach out now and let our expertise guide you.

    Optical Properties and Metrology Testing

    Leveraging our in-house, state-of-the-art metrology laboratory, we guarantee that your caesium iodide components will meet and exceed your expectations. This commitment to quality and precision underlines every product we supply. Discover more about our testing facilities here. Please contact our technical sales team who will guide you through your enquiry.

    Below is a brief summary of caesium iodide’s optical properties, a full data sheet is available here.

    Transmission Range0.25 to 55µm
    Refractive Index1.73916 @ 10µm
    Density4.51 g/cm3
    Melting Point621°C
    HardnessKnoop 20 with 200g indenter
    Diameter< 5mm to 50mm +
    Form error (@633nm)< 0.25 waves
    Centration/parallelism< 1 arc minute
    Scratch/dig< 20/10
    Typical coatingsBBAR @ 1.2-3µm

    Frequently Asked Questions

    Caesium iodide (CsI) is a crystalline material commonly used in the optical and radiation detection industries. Due to its high density and effective atomic number, it is particularly useful as a scintillator for detecting gamma radiation. CsI is also employed in optical components like windows and lenses, especially in infrared and deep ultraviolet applications, due to its wide transmission range and ability to withstand harsh environments.

    A caesium iodide scintillator works by converting gamma radiation into visible light. When gamma rays enter the CsI crystal, they interact with the material and cause it to luminesce or “scintillate.” This emitted light is then detected and converted into electrical signals, providing valuable data for radiation detection and measurement. CsI scintillators are known for their high light yield and quick response time, making them effective for various radiation detection applications.

    Yes, custom caesium iodide components can be ordered to meet specific optical or radiation detection requirements. Customizations can include specific dimensions, thicknesses, and shapes, as well as additional features like anti-reflective coatings. Knight Optical offers bespoke CsI components, ensuring they fit perfectly into your unique systems, whether for industrial, medical, or scientific applications.

    Caesium iodide windows offer several advantages in optical systems, including broad transmission range from deep ultraviolet to far-infrared wavelengths, high resistance to mechanical and thermal shock, and good scintillation properties. These attributes make CsI windows ideal for spectroscopy, imaging systems, and scintillation detectors, providing clear, precise, and stable optical performance in a variety of environments.

    Caesium iodide lenses are beneficial in infrared applications due to their high refractive index, which allows for superior focusing and imaging performance in the IR spectrum. CsI lenses are also relatively soft and hygroscopic, allowing for precision polishing and coating, which enhances their infrared transmission capabilities. They are particularly suited for thermal imaging, IR spectroscopy, and other IR applications requiring high-quality, transparent optical media.

    Caesium iodide optical components can be purchased from specialized suppliers like Knight Optical, which provides a range of CsI products, including scintillators, windows, and lenses. They offer high-quality, custom-fabricated CsI components tailored to the requirements of various industries, ensuring optimal performance for specific applications. Their expert team can also provide advice and support to help you select the right CsI solutions for your optical or radiation detection needs.


    Is your question not here?

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



    Caesium iodide is a very soft material with a hardness of HK20 and therefore can be difficult to polish.


    Due to the materials’ degradation when in contact with moisture, it is often coated and stored within a desiccator to minimise any interactions with the atmosphere.

    Typical Applications

    Scintillator for Caesium Iodide


    Caesium Iodide can be doped with Thallium to create CsI(Tl) which creates one of the brightest scintillators, emitting at wavelengths that work well with Silicon photodiodes.

    Interference Bandpass Filters for ANPR Cameras

    Security Imaging Systems

    Arrays of CsI (often doped with Thallium) can be used in security imaging systems including baggage scanners.

    Germanium for Fourier Transform Infrared Spectroscopy (FTIR)

    FTIR Spectrometers

    Caesium Iodide is commonly used in infrared spectroscopic windows due to its exceedingly large transmission band.

    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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