This article mainly introduces the applicable bands, applications, features, advantages and disadvantages of Common Optical Substrate.

K9 (H-K9L, N-BK7) is the most commonly used optical material, with excellent transmittance from visible to near-infrared (350-2000nm), and is widely used in telescopes, lasers and other fields. H-K9L (N-BK7) is the most commonly used optical glass for preparing high-quality optical components. When the additional advantages of UV fused silica (good transmittance and low thermal expansion coefficient in the UV band) are not required, it is generally Will choose H-K9L.

Ultraviolet fused silica (JGS1, F_SILICA) has high transmittance from ultraviolet to near-infrared band (185-2100nm), and has high transmittance in the deep ultraviolet region, making it widely used in ultraviolet lasers. In addition, compared to H-K9L (N-BK7), UV-grade fused silica has better uniformity and lower thermal expansion coefficient, making it particularly suitable for applications in the ultraviolet to near-infrared band, high-power lasers, and imaging.

Due to the high transmittance of calcium fluoride (CaF2) within the wavelength range of 180nm-8um (especially in the 350nm-7um band, the transmittance exceeds 90%), the refractive index is low (for the operating wavelength range of 180 nm to 8.0um, its The index of refraction varies from 1.35 to 1.51) so there is high transmission even without coating. It is often used as windows and lenses in spectrometers, as well as in thermal imaging systems. In addition, due to its high laser damage threshold, it has a good application in excimer lasers. Compared with similar substances such as barium fluoride and magnesium fluoride, calcium fluoride has higher hardness.

Barium fluoride material has high transmittance from 200nm-11um region. Although this characteristic is similar to calcium fluoride, barium fluoride still has better transmission after 10.0um, while calcium fluoride has a linear decline; and barium fluoride can withstand stronger high-energy radiation. However, the disadvantage of barium fluoride is its poor water resistance. When exposed to water, performance degrades significantly at 500°C, but in dry environments it can be used for applications up to 800°C. At the same time, barium fluoride has excellent scintillation properties, and can be made into various optical components such as infrared and ultraviolet. It should be noted that when handling optics made of barium fluoride, gloves must be worn at all times, and hands must be washed thoroughly after handling.

Magnesium fluoride is popular in many UV and IR applications and is ideal for applications in the 200nm-6um wavelength range. Compared to other materials, magnesium fluoride is particularly durable in the deep ultraviolet and far infrared wavelength range. Magnesium fluoride is a strong material that can be used to resist chemical corrosion, laser damage, mechanical shock and thermal shock. Its material is harder than calcium fluoride crystals, but relatively softer than fused silica, and has slight hydrolysis. It has a Knoop hardness of 415 and a refractive index of 1.38.

Zinc selenide has a high transmittance in the 600nm-16um band, and is often used in thermal imaging, infrared imaging, and medical systems. Moreover, due to the low absorption rate of zinc selenide, it is especially suitable for high-power CO2 lasers. It should be noted that zinc selenide material is relatively soft (Knoop hardness of 120), easy to scratch, and it is not recommended to be used in harsh environments. Be extra careful when handling and cleaning, and use even force when holding or wiping. It is best to wear gloves or rubber finger cots to prevent contamination. Do not hold with tweezers or other tools.

Silicon is suitable for use in the near-infrared band in the 1.2-8um region. Because silicon material has the characteristics of low density (its density is half that of germanium material or zinc selenide material), it is especially suitable for some occasions sensitive to weight requirements, especially in the application of 3-5um band. Silicon has a Knoop hardness of 1150, which is harder than germanium and less brittle than germanium. However, it is not suitable for CO2 laser transmission applications due to its strong absorption band at 9um.

Germanium is suitable for use in the near-infrared band in the 2-16um region, and is very suitable for infrared lasers. Due to germanium’s high index of refraction, minimal surface curvature, and low chromatic aberration, corrections are usually not required in low-power imaging systems. However, germanium is seriously affected by temperature, and the transmittance decreases with the increase of temperature. Therefore, it can only be used below 100 °C. The density of germanium (5.33g/cm³) should be considered when designing systems with stringent weight requirements. The germanium plano-convex lens is surface-turned with a precision diamond lathe, a feature that makes it ideal for a variety of infrared applications, including thermal imaging systems, infrared beamsplitters, telemetry, and forward-looking infrared (FLIR).