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Custom Potassium Chloride

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Find out more about our custom potassium chloride

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At Knight Optical, we supply a diverse array of potassium chloride optical components, including precision windows and ground blanks. We cater to your specific needs by providing both uncoated and coated options, featuring broadband antireflective (BBAR) coatings.

Our products are designed to meet a broad potassium chloride wavelength range, ensuring optimal performance in your applications. 

Potassium chloride (KCl) is a crystalline material often used as a sputter window in CO2 lasers. Its wide transmission band means it has extensive optical applications across various wavelengths, making it suitable for UV, visible, mid-wave, and far-IR regions. This adaptability underscores its importance in potassium chloride optics uses.

If your requirements extend beyond our standard range, our technical sales team is ready to assist. We continually expand our capabilities to meet the evolving demands of the optical industry, ensuring we can provide solutions specifically for your potassium chloride wavelength and refractive index requirements.

Speak to our experts about your Custom Potassium Chloride needs today

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    Optical Properties of Potassium Chloride

    Understanding the critical role of potassium chloride’s refractive index in optical performance, we ensure our components meet strict quality standards. Our in-house metrology laboratory, equipped with state-of-the-art technology, allows us to guarantee that your potassium chloride optics align with your exact specifications.

    For those exploring potassium chloride optics uses in various industries, including scientific research, medical devices, and defence systems, Knight Optical is your trusted partner. Our commitment to quality and our ability to provide custom solutions make us an ideal choice for your optical needs.

    Below is a brief summary of potassium bromide’s optical properties.

    Transmission Range0.21 to 20µm
    Refractive Index1.45644 @ 10µm
    Density1.99 g/cm3
    Melting Point776°C
    HardnessKnoop 7.2 <110>, 9.3 <100> with 200g indenter
    Diameter< 5mm to 80mm
    Form error (@633nm)< 0.25 waves
    Centration/parallelism< 1 arc minute
    Scratch/dig< 40/20
    Typical coatingsBBAR @ 1-20µm, DLC @ 1-20µm

    Frequently Asked Questions

    Potassium chloride (KCl) is widely used across different sectors. In the optical industry, KCl was once employed for infrared optics but has been replaced by more durable materials. However, it’s still used in some specific optical applications like Fourier-transform infrared spectroscopy (FTIR). Beyond optics, KCl is a fundamental component in medicine, food processing, as a salt substitute, and in agriculture as a fertilizer component. It’s also employed in scientific applications and as a flux in glass manufacturing due to its clarity-enhancing properties​​​​.

    Although its use has declined due to hygroscopic issues (meaning it absorbs moisture), KCl was historically used in infrared optics for its wide transmission range from UV to far-infrared light. Nowadays, KCl might still be used in FTIR spectroscopy applications as it allows for the efficient transmission of infrared light. However, care must be taken to protect KCl components from moisture to prevent degradation​​​​.

    The effectiveness of potassium chloride in optical uses, especially in spectroscopy, is largely due to its broad transmission range, from 210 nm to 20 µm. Potassium chloride’s wavelength is suitable for various spectroscopic techniques and CO2 laser applications, though its hygroscopic nature limits its long-term use unless it’s properly protected or used in controlled environments​​.

    KCl’s low refractive index makes it an ideal candidate for use in certain optical applications, such as CO2 laser applications and infrared spectroscopy, where low absorption and high damage thresholds are crucial. However, the exact value of the refractive index and how it influences optical performance should be considered in the design of optical systems​​.

    Potassium Chloride optics, like windows and lenses for infrared applications, can be purchased from specialized optical manufacturers and suppliers. The cost can vary based on the size, thickness, and quality of the material, as well as the current market supply and demand for KCl. For specific dimensions and customisations, prices will vary. Contacting suppliers directly for quotations is advised​​.

    In scientific research, KCl optics are mainly used in FTIR spectroscopy and other infrared-related applications. Their main benefit lies in their broad infrared transmission capabilities, making them suitable for analyzing a wide range of materials. However, due to their hygroscopic nature, their application is more suited for short-term projects or environments where moisture control is possible.

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    Additional Information


    Potassium chloride is grown via the Kyropoulos method , and cleaves easily. It is slightly more durable than potassium bromide but its transmission does not extend as far in the IR region.



    KCl is extremely soft so care needs to be taken when handling. It is also very hygroscopic so needs to be kept in a moisture-free environment., or a protective coating should be applied to the exposed surface.

    Typical Applications

    Infrared Lenses for Low Powered CO2 Lasers

    Laser windows

    KCl is often used as a disposable protective window in CO2 laser systems due to its low refractive index, low absorption, and high damage threshold.

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    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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