At Shanghai Optics we produce a wide range of quality infrared optics, including lenses, prisms, windows, mirrors, and laser and imaging assemblies. Our state of the art equipment allows us to achieve unparalleled precision and surface quality, and every piece we manufacture is subject to stringent quality controls.
Our diamond turning machines enable us to produce sub-nanometer level surface finishes and form accuracies to the sub-micrometer. Each diamond-turned IR optical component is manufactured individually, and can be customized to your exact form specifications for IR applications.
Our diamond fly cutting machine allows us to generate precision diffraction gratings and other linear elements on optical elements with contoured diamond shapes.
We offer a wide range of IR substrates, including Ge, Si, ZnSe, ZnS, ZnS , CaF2, BaF2,and GaAs. Our lenses and windows are available with multiple anti-reflection coating options that can increase durability and improve performance.
Infrared optics have applications in a many fields, from high power CO2 lasers, which work at 10.6 μm, to night-vision thermal imaging (MWIR and LWIR bands) and IR imaging. They are also important in spectroscopy, as the transitions used in identifying many trace gases are in the mid infrared region. We produce laser line optics as well as infrared components which perform well over a wide wavelength range, and our experienced IR team can provide full design support and consultation.
The infrared region, between 0.750 and 1000μm (750 – 1000000nm) is often divided into three sub regions: the near infrared, or NIR, between 0.750 and 3μm, the mid-wave infrared (MWIR), between 3 and 30μm, and the far infrared (FIR) from 30 to 1000μm. Your choice of substrate and anti-reflection coating will depend on which wavelength requires prime transmittance in your application. For instance, if you are transmitting light in the MWIR, germanium may be a good choice. For NIR applications, sapphire may be ideal.
Other specifications you may want to consider in your choice of infrared optics include thermal properties and index of refraction.
The thermal properties of a substrate quantify how it reacts to heat. Often, infrared optical components will be exposed to widely varying temperatures. Some IR applications also produce a large amount of heat. To determine whether an IR substrate is suitable for your application you will want to check the index gradient and coefficient of thermal expansion (CTE). If a given substrate has a high index gradient, it may have suboptimal optical performance when used in a thermally volatile setting. If it has a high CTE, it may expand or contract at a high rate given a large change in temperature.
The materials most often used in infrared optics vary widely in index of refraction. Germanium, for instance, has an index of refraction of 4.0003, compared with 1.413 for MgF. The availability of substrates with this wide range of index of refraction gives added flexibility in system design.
The dispersion of an IR material measures the change in index of wavelength with respect to wavelength as well as the chromatic aberration, or the separation of wavelength. Dispersion is quantified, inversely, with the Abbe number, which is defined as ratio of the the refractive index at the d wavelength minus 1, over the difference between the index of refraction at the f and c lines. If a substrate has an Abbe number of greater than 55, it is less dispersive and we call it a crown material. More dispersive substrates with Abbe numbers of lower than 55 are called flint materials.
Germanium Ge is a good choice for optical lenses, windows, and prisms, and it performs well without infrared anti-reflection coatings. It transmits from 2 to 13µm. The high Knoop Hardness (780) makes it ideal for applications where durability is key, but it can only be used at temperatures below 100°C.
Barium fluoride BaF2 is often used for IR spectroscopy, as its properties include wide broadband transmission and a low index of refraction (1.48). BaF2 can remain stable up to 800°C, but is resistant to thermal shock and should be used in a dry environment. Knoop Hardness is 82.
Zinc Selenide ZnSe infrared optics have a high resistance to thermal shock, which makes them a good choice for thermal imaging systems and CO2 laser systems. The index of refraction nd is 2.403. ZnSe optics are not as durable as other options and we do not recommend them for optical systems in harsh environments.
Magnesium Flouride MgF2 is more rugged and durable than ZnSe, and offers very good transmission from 120nm to 7μm. The index of refraction, at 1.413, is the lowest index of refraction for commonly used IR substrates. MgF has a density of 3.11 g/cm3, a Knoop hardness of 415, and is resistant to both chemical etching and laser damage.
Gallium Arsenide GaAs optical components transmit over 40% between 2µm to 15µm and are very hard and dense. A Knoop Hardness of 750 makes them comparable to Germanium optics, but the index of refraction is slightly lower at 3.3. Our GaAs lenses and windows are coated with a broadband antireflective optical coating to improve performance.
IR grade fused Silica has a reduced amount of OH- ions as compared to other grades of Silica, and this provides a higher transmission in NIR wavelength ranges. Fused silica offers consistent, repeatable performance and a low thermal expansion coefficient. IR material is more expensive to produce than UV-grade fused Silica but is still more budget-friendly than other options.
We are able to customize IR lenses, windows, filters, and other optical components to meet the requirements of your application, and our design team can work with you as you go from prototype stage to production. Our wide range of choice in substrates and optical coatings, coupled with state of the art machinery and metrology lab, ensure that your device will be fitted with the highest quality optics.