Optical components are crafted from various substrates,and the choice of materials considerably influences their effectiveness for particular applications. In this article, Knight Optical delves into some of the most prevalent substrates utilized in infrared applications, highlighting their typical uses.
Sapphire (Al2O3)
When one thinks of sapphire, images of exquisite, deep-blue jewelry often come to mind. However,in the realm of optical components,Sapphire,or Al2O3,is a powerhouse.
Engineered synthetically for optical applications, Sapphire is renowned for its toughness, chemical resistance, and exceptional thermal conductivity. It ranks as the second hardest crystal, following diamond, making it a preferred choice for engineers and manufacturers seeking robust optical solutions.
Applications of Sapphire Optical Components
Sapphire is versatile and can be utilized in various optical forms, including Windows, Lightguides, Lenses, and Prisms. Its scratch-resistant nature makes it a popular choice for luxury watch faces,and it is also found in Windows for laser medical devices and underwater cameras.
Discover more about the benefits of choosing Sapphire here.
Germanium (Ge)
Germanium, sharing a crystal structure with diamond, is favored for infrared (IR) applications. As a high-density substrate,it is often employed in scenarios where weight is not a primary concern. Though, it is indeed critically important to note that Germanium is not suitable for environments exceeding 100ºC.
Applications of Germanium (Ge) Optical Components
Typically, Germanium is found in IR wavelength applications. It is commonly used in Longpass Filters, which block visible and UV light, as well as in Prisms for FTIR spectroscopy, and in Windows and Lenses for forward-looking infrared (FLIR) systems and thermal imaging technologies.
Learn more about the advantages of selecting Germanium optics here.
Zinc Selenide (ZnSe)
Zinc Selenide (ZnSe) is a polycrystalline substrate that effectively transmits wavelengths from 600nm to 21µm, achieving approximately 70% transmission between 1 and 15µm. Despite being a hazardous material, ZnSe is chemically inert, high in purity, and has a meaningful damage threshold.
Applications of Zinc Selenide (ZnSe) Optical Components
ZnSe is widely used in CO2 laser systems, particularly as laser-grade IR Lenses and Beam Combiners. it also serves in various optical forms, including Resonator and Optical Windows, which seperate the gas medium from resonator optics and protect in FLIR and thermal imaging applications, respectively, and also in Prisms.
Learn more about the advantages of choosing ZnSe optics here.
Zinc Sulphide (ZnS)
Softer than ZnSe, Zinc Sulphide (ZnS) is a commonly used IR-transmitting material that forms various optical components, including Lenses, Prisms, Windows, and Blanks. It appears pale yellow to clear and transmits about 50% between 0.4 and 12μm, with a drop-off to zero near 15μm.
Applications of Zinc Sulphide (ZnS) Optical Components
Similar to ZnSe, this substrate is highly sought after for CO2 lasers, particularly in the form of Resonator Windows, due to its low absorbance in the IR spectrum, as well as for FLIR systems.
Learn more about the advantages of selecting ZnS optics here.
Silicon (Si)
Silicon (Si) is one of the hardest minerals and optical materials available for use in the near-infrared (NIR) range [1µm] up to about 6µm. It is indeed frequently enough chosen as a lighter alternative to Germanium due to its lower density and refractive index.
Applications of Silicon (Si) Optical Components
silicon is frequently utilized in the form of Windows and lenses, serving as a lightweight and cost-effective option for NIR and medium-wave infrared (MWIR) thermal imaging applications.
Learn more about the advantages of choosing Si optics here.
Crystalline Quartz (SiO2)
Crystalline Quartz (SiO2) is a naturally occurring birefringent material that transmits at 90% between 0.18 and 3.5µm, making it suitable for applications in the ultraviolet (UV) to near-infrared (NIR) spectrum. Known for its high purity and water insolubility, SiO2 is also birefringent.
Applications of Crystalline Quartz (SiO2) Optical Components
SiO2 is effective at temperatures below 490°C and is commonly found in Windows, Prisms, Beamsplitters, and Waveplates, the latter being used in applications involving lasers or IR light sources due to its high damage threshold.
Learn more about the advantages of selecting SiO2 optics here.
Gallium Arsenide (GaAs)
Gallium Arsenide (GaAs) is a robust IR-transmitting material that shares many mechanical characteristics with Germanium. With a hardness rating of HK750, it is chemically stable and non-hygroscopic. It transmits around 40% between 2 and 15µm, and applying a broadband antireflective (BBAR) coating can enhance its spectral performance.
Applications of Gallium Arsenide (GaAs) Optical Components
Due to its durability and transmission capabilities in both medium-wave infrared (MWIR) [3 and 5µm] and long-wave infrared (LWIR) [8 and 12µm] bands, gaas Lenses and Windows are ideal for FLIR systems. Additionally, it is indeed currently the most efficient material for converting solar energy into electricity, making it a popular choice for high-efficiency solar cells.
Learn more about the advantages of selecting gaas optics here.
The aforementioned substrates represent just a selection of those commonly used in IR-operating systems. For a thorough list of our IR substrates, please click here.
If you are in search of high-quality, custom optical components, please reach out to a member of our Technical Sales Team.
