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Custom Sodium Chloride

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Knight Optical offers a wide range of high-quality sodium chloride optics, including sodium chloride lenses and windows, specifically to meet diverse application needs.

Sodium chloride (NaCl), commonly known as rock salt, is renowned for its excellent optical properties, notably its broad transmission range from 200nm to 15µm and a refractive index of sodium chloride that ensures high clarity and minimal optical distortion.

At Knight Optical, we understand the critical nature of optical performance, which is why our sodium chloride lenses and other optical components are created to provide optimal refractive index consistency. Whether you’re looking for standard or custom solutions, our dedicated team is here to assist with your specific requirements, ensuring your optical components like sodium chloride ground blanks and windows meet the precise sodium chloride refractive index specifications needed for your projects.

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    Optical Properties of Sodium Chloride

    For those in need of coated optics, we offer a range of coatings, including broadband antireflective (BBAR) coatings, to improve the performance of our sodium chloride optics. Our commitment to quality and customer service ensures that whether you require a single sodium chloride lens or a comprehensive set of optics, Knight Optical is your trusted partner in precision optics.

    Our sodium chloride optical components are designed for precision and reliability, with each piece thoroughly tested in our cutting-edge metrology lab to ensure they meet the high standards expected by our clients. The NaCl refractive index plays a crucial role in the performance of our optics, making them ideal for a variety of applications, from scientific research to medical instruments.

    If your specific requirements are not listed, please contact our technical sales team, who will guide you through your enquiry, ensuring your optical components perfectly match the sodium chloride refractive index and other specifications needed for your application.

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

    Transmission Range0.2 to 16µm
    Refractive Index1.49065 @ 10.6µm
    Density2.17 g/cm3
    Melting Point801°C
    HardnessKnoop 18.2 in <100> with 200g indenter
    Operating Temperature< 400°C in dry environment
    Diameter< 5mm to 200mm
    Form error (@633nm)< 0.25 waves
    Centration/parallelism< 1 arc minute
    Scratch/dig< 80/50
    Typical coatingsBBAR @ 1-16µm, DLC @ 1-16µm

    Frequently Asked Questions

    The refractive index of Sodium Chloride varies with the wavelength of light used. However, it is generally around 1.5 for visible light. This property makes NaCl optics suitable for various applications where light bending is required.

    Sodium Chloride optics are popular in infrared applications due to NaCl’s high transmission rates in the IR spectrum, making them ideal for IR spectroscopy and thermal imaging systems.

    Sodium Chloride offers excellent transparency in the infrared range, which is superior for specific applications compared to materials with lower IR transmission. However, it is softer and more hygroscopic, requiring careful handling and storage conditions.

    Sodium Chloride lenses can operate at higher temperatures than some other optical materials but are susceptible to moisture and should be protected from exposure to humid environments to prevent degradation.

    Common applications include thermal imaging, IR spectroscopy, and other IR applications where high transmission in the infrared range is crucial. NaCl optics are chosen for their performance in these specific wavelengths.

    Due to its hygroscopic nature, Sodium Chloride optics should be stored in a dry, controlled environment and should be cleaned with care, avoiding any solvents that might dissolve or damage the surface.

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    Additional Information

    Crystalline growth

    Sodium chloride is grown via the Kyropoulos method and, under humidity-controlled conditions, can be highly polished.


    It is a relatively low cost material.

    Shock resistance

    NaCl is relatively resistant to mechanical and thermal shock.



    Sodium chloride is hygroscopic, so requires protection from atmospheric conditions due to moisture degradation. A hydrophilic coating can help protect it from ‘fogging’ up when in contact with moisture.

    Careful handling

    It requires very careful handling as, with a hardness of HK18.2, it is extremely soft.


    Do not clean NaCl optics with water.



    We can offer broadband antirelective (BBAR) coatings for your sodium chloride.

    Typical Applications

    Germanium for Fourier Transform Infrared Spectroscopy (FTIR)

    Fourier Transform Infrared Spectroscopy (FTIR)

    NaCl optics, including cell windows, are used in FTIR spectrometers, due to its wide transmission range into the infrared region. They can be used to hold non-polar liquid samples, which will not degrade the material.

    Aspherical Lenses for Laser Beam Shaping

    High-powered laser systems

    Sodium chloride windows can be used in high-powered laser systems, such as CO2 lasers due to its low absorption. They are often used to protect other laser optics such as zinc selenide or YAG focussing lenses.

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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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