What is an Optical Window?

university wafer substrates

Shielding Photodectors from UV-Light

A corporate researcher requested the following quote:

We received our order for 100mm undoped Ge optical grade wafers and are already working with it. We did not run into any problems.

We use the Germanium (Ge) as an optical window in the infrared regime. Mainly we want to shield our photodetectors from visible and uv-light but still have the infrared light on them.

Reference #224204 for specs and pricing.

Get Your Quote FAST! Or, Buy Online and Start Researching Today!

BK-7 Glass Used for Optical Windows

A postdoc requested the following quote:

We’re looking for an optical window (BK7), 0.2 mm thick, coated with a thin layer (20 nm, for example) of a high index material such as polySi or TiO2.

Do you have such windows?

Reference #180569 for specs and pricing.

Infrared Grade Silicon Substrate Used for IR Transmission

A corporate scientist requested the following quote:

I’m looking to purchase: 4” wafer 0.5mm thick DSP Infrared grade (high transmission near 10.0um) Uniform refractive index Qty: 1 or 2 It’s to be used as an optical window for IR transmission. 

Reference #268835 for specs and pricing.

What is an Optical Window?

Optical windows are transparent plates made of silicon glass, quattz, plastic, or sapphire that are usedwhat odes an optical window look like to eliminate unwanted light in a system while allowing desired light to pass through. These windows have distinct optical absorption characteristics that allow them to absorb laser light at certain wavelengths and transmit other wavelengths with minimal optical attenuation. Optical windows are used in many optical applications including spectroscopy and imaging systems because they allow for precise spectral profiles and control of the transmitted laser beams. For example, compact supercontinuum lasers require special UV-grade fused silica or sapphire windows for efficient transmission of laser beams over the entire ultraviolet spectrum. Optical Windows also help reduce background noise from ambient sources by blocking out infrared radiation from entering the system. They ensure only desired components of the beam enter into the apparatus which helps improve resolution and accuracy in any application requiring precise control over light transmission. 

Optical Windows to Protect Infrared Sensors

A project manager fighting the plastic pollution of the oceans requested the following quote:

We are currently designing a spectrometer to identify the plastic types, using the near infrared spectrum. I am looking for an optical window to protect an infrared sensor. I need a material with a very low absorption on the 850-1700nm wavelength band (BK-7, Fused silica, H-K9L…). Regarding the dimensions: Shape : Circular or square Dimensions : between 10 and 25 mm (side or diameter).

UniversityWafer, Inc. Quoted:

We can supply Fused silica JGS1.

Dia Thick Surface TTV Top/Back side Ra S/D
25 mm±0.2mm 3 mm ± 0.1 mm DSP <10um <1nm 40/20

Reference #271458 for specs and pricing.

What are Silicon Optical Windows?

Silicon Optical Window is an optical window made from specified optical grade silicon. These windows are used in infrared optics and IR wavelength regions, providing superior transmission for those applications that require optical materials with high-purity monocrystalline silicon substrates. It is also ideal for light transmission in the UV and longer wavelengths due to its high purity, making it a perfect material for processing various applications. In addition to its superior performance compared to glass or other materials, it also offers lower cost than other materials such as calcium fluoride or silicon germanium windows.

Racetrack Silicon Optical Windows for Infrared Detection

Racetrack type silicon optical window.


Material Silicon
Size 107mm-0.1*165mm-0.1
Thickness 12.2mm +/-0.05
Chamfer 0.5x45 deg
Clear Aperture 90%
Surface Quality 60-40
Parallelism <1 arc minutes
Angle of Incidence 0 deg
Coating AR+DLC@3-5um
Transmittance >96%


Optical Windows

Our research clients use the following fused silica specifications for their optical windows applications.

50.8mm 100 micron DSP

Please let us know if you can use this spec or if we can quote you on another spec?

[Sources: 0, 4]

The optical windows and mirrors are made of hard materials such as quartz and quartz. For example, some had to be made on cheaper substrates such as borosilicate glass, and others, such as the ones mentioned above, had to be made on a more expensive substrate such as glass with higher hardness and rigidity. [Sources: 4, 5]

Direct transmission measurements of brain tissue have shown that the wavelength of the golden window is optimal for NIR deep brain imaging. The material of the mounting window cells must be close to the window substrate of CTE in order to correspond to the wavelength of the optical window (by means of fixed mounting and to reduce window stress and temperature changes 2,5) and be able to withstand heavy abrasion from the environment and significantly improve the transmission of naked windows. [Sources: 0, 1]

Near - infrared supercontinuum laser sources (NIR) and Near - Infrared optical lamp sources have been used to imaging deep brain tissue under a variety of conditions, compared to imaging lamps and sources. Near, infrared, near-infrared and ultraviolet laser beams were all imaged at high sensitivity and high resolution in the presence of light, compared to image lamps or sources with very low sensitivity. [Sources: 1]

The TPX is optically transparent in the visible (THz) range, so that HeNe laser beams can be used for alignment. This makes it ideal for multispectral applications that require a single window to transmit desired wavelengths. A simple example of such a window is one that offers high transmission of a desired wavelength while protecting the rest of the optical elements from dust and dirt. Three windows have been set when the glass will allow a higher throughput. [Sources: 0, 2, 7]

Size and number of optical windows are determined by the outer housing configuration; see System specifications for window size and quantities. Normally these windows are used as the inside and outside windows of the sample chamber, unless otherwise stated. [Sources: 7]

If you cannot find the flat optical window you are looking for, please use our enquiry form and send us your wishes. Below we have found a list of materials whose materials are mainly incorporated into the windows of optical apartments. [Sources: 3]

This should help you to choose the optimal material that is the most economical solution for your optical application. These are very versatile optical materials that are easy to manufacture in high quality, are inexpensive and suitable for a wide range of applications such as optical windows. [Sources: 0, 3]

These have a high transmissivity of visible light and are suitable for a wide range of applications, such as the increasing demands on high-resolution imaging systems. These applications include the imaging system with ultraviolet wavelengths. In the field of medical imaging and other applications, there is an increasing need for optical windows. [Sources: 3, 7]

These are important applications that require a better understanding of the effects of high speeds. Although windows provide protection to optical systems, they are not always the most important optical element in the system, which can make them one of the most expensive 3. Since windows are sometimes referred to as "resistance windows," it is worth understanding the dynamics of a high-speed impact on them. [Sources: 0, 6]

As well as the production time and price, and the impact of high-speed influences on the optical element itself, and also the production times and prices. [Sources: 4]

The topics discussed here are intended for the introduction of optical windows only, and only a few aspects of window design are presented. There are several factors a designer must consider when designing a window for an optical system, including the size of the window, the type of windows, and the number of elements in the system. When designing optical systems, it is very important to include windows in early optical designs. Therefore, it is very important to consider the optical window as a driven element in a system that can compensate for the aberrations caused by the windows. [Sources: 0]

The windows may be simple planes or parallel plates, but they can distort or decrease the performance of the optical system. Optical mirrors and windows are subjected to blocking techniques that can increase the reject rate. To achieve tight thickness tolerances, the window cannot simply be a plane parallel to the panel or a parallel panel. [Sources: 0, 4]

Optical windows are often coated with JNS, but anti-reflection coatings at certain wavelengths are also part of this capability. BK7 is made of a wide range of materials such as polyurethane, polycarbonate and other materials. Optical windows are manufactured and planed with almost all available materials on request. [Sources: 3, 5]


[1]: https://spie.org/news/6401-an-optical-window-for-deep-brain-imaging

[2]: https://vividcomm.com/2018/12/23/optical-fibre-three-windows/

[4]: https://optimisticmommy.com/6-steps-to-choosing-the-correct-optical-window-or-mirror/

[6]: https://aip.scitation.org/doi/10.1063/1.5055676

[7]: https://www.montanainstruments.com/Accessories/Windows/

Why Use Fused Silica to Make Optical Windows?

When it comes to the making of optical windows, why use fused silica? This material is inert, which means that it is not affected by the presence of any chemical agents. This is especially important in optical applications, where high optical homogeneity is needed. Likewise, there are many grades of fused silica that can vary in UV and infrared transmission. Read on to discover the advantages of fused silica for optical windows.

substrates used in optical windows

Borosilicate glass

Borosilicate glass has excellent thermal shock resistance and is also used for high-precision optical components. This material is also used in the fabrication of hot mirrors for scientific applications, such as detecting infrared light and protecting delicate optical systems. Because it is resistant to high temperatures, borosilicate glass is an excellent choice for optical windows. Its many uses range from laboratory experiments to household baking.

In optical windows, borosilicate is more durable than soda lime glass. It is much harder and has a lower coefficient of expansion than soda lime glass. It is also more resistant to chemical agents than soda lime glass. In addition, it has a higher refractive index and can withstand continuous temperatures of 450 degrees Celsius. Optical windows made of borosilicate glass are generally stronger and scratch-resistant than soda lime glass.

Optical windows made of borosilicate glass may be coated with other materials. For example, synthetic CaF2 glass is often used for lasers with a 1.064 um wavelength. In addition, this material exhibits high homogeneity and good mechanical properties, making it ideal for UV applications. While most optical windows are made of borosilicate glass, some may require a UV-transmitting glass, in which case the cutoff wavelength is around 185 nm.

Fused Silica Optical Windows

Fused silica is an excellent material for making optical windows. Its excellent transmission characteristics span a wide range of wavelengths, including infrared (IR) and visible light (VIS) waves. Fused silica has excellent transparency in the ultraviolet region and is fluorescent-free. It also has excellent optical properties, including low autofluorescence and scattering. Its high-grade properties make it an excellent choice for windows in harsh environments, as it resists chemicals, is very resistant to temperature changes, and has high crystalline purity.

Fused silica has many advantages over natural quartz crystals for optical windows. Its high glass transition temperature makes it suitable for high-temperature applications, and its high resistance to thermal shock and low thermal expansion coefficient makes it ideal for optical windows and rods. It can be made in thicknesses ranging from 0.15 mm to 150 mm, and coated with a high-quality coating.

Fused silica's high transmittance makes it ideal for optical windows and prisms, beam-splitters, and refractors. Its low thermal conductivity makes it an excellent thermal insulator, and its high DUV transparency makes it an excellent choice for photolythography. When it comes to temperature resistance, fused silica is a solid choice.

Single Crystal Quartz Optical Windows

There are several advantages of quartz glass. First, it is highly transparent in the visible spectrum, allowing light to pass through it without distortion. Second, quartz is highly resistant to high energy and ultra-violet radiation. Third, it can be produced with extreme thickness and ultra-thinness. Fourth, quartz can be used in the manufacturing of optical windows and other optical components. Last, quartz is also a popular material for making optical windows, lenses, and polarizers.

For optical windows, quartz is often made with diamond lenses. These lenses are durable and have a high transmittance, but are not scratch resistant. In addition, the price of diamond windows limits their practical size. Single crystal quartz has been studied as an alternative for optical windows, because of its high transmittance and low surface defect. Optical windows can be made up to 4.000" in diameter. Quartz is also used for other kinds of optical components, including lenses and prisms.

Due to its low refractive index, quartz can be etched or metallised, which makes it ideal for high-precision microwave circuits. Further, due to its low dielectric constant, quartz is a good choice for applications that require high-performance narrowband filters. And, thanks to its low temperature, quartz is easier to temper than other materials. It is also three times stronger than untempered glass, so it's ideal for optical windows and other optical components.

Fused Silica Chemical Inertness

Fused silica is a chemically inert material. It will not react to a variety of common compounds, including hydrofluoric acid. This property makes it particularly useful for optical windows in environments where high temperatures are a frequent occurrence, and for laboratory tools that are regularly exposed to caustic chemicals. Fused silica is incredibly inert, and only a few uncommon materials are capable of attacking it.

A highly pure form of fused silica is obtained by burning the chemical compound silica tetrachloride in a vapor-free plasma flame. The silica tetrachloride reacts with oxygen and escapes in the form of HCl. This vapor-free plasma flame then fused the silica into a solid. This material is known as BK 7 and demonstrates excellent optical transmission and diffusion blocking.

While glass and fused silica are comparable in tensile strength, fused silica is stronger due to its higher hydroxyl content. Fused quartz is more inert than raw quartz, and has several advantages. Raw quartz is more durable than fused silica. The chemical inertness of fused quartz makes it the perfect material for optical windows and many other uses.

Low Autofluorescence

When comparing the qualities of common glass window materials, fused silica is the clear winner. Fused silica is non-toxic and exhibits high radiation and thermal resistance, making it a great choice for windows and other optical parts in laboratory equipment and harsh environments. Its excellent transmission properties allow it to transmit both visible and infrared light. As a result, it is also an excellent choice for high-quality, thin optical windows and lenses.

This material's unique properties allow it to be used for a variety of applications, including laser lighting. Fused silica optical windows focus and separate light for applications ranging from cutting to laser lighting. Low autofluorescence is another characteristic of fused silica, which makes it particularly useful for laser-powered cutting. Since fused silica can withstand high processing temperatures, it has many applications.

To determine which of these materials exhibits low autofluorescence, an inversion microscope system equipped with an emission filter (540-550 nm) and a dichromatic mirror was used. Four samples were used for each condition. The auto-fluorescence brightness of each polymer was measured as follows:

No Birefringence

The birefringence of oblate nanopores in fused silica has been simulated using simulation methods. Its retardance was 150 nm with a density of 10-4 and an interline spacing of 1 mm. Despite its low birefringence, it retains high transparency. This effect is the result of an imprinted birefringent pattern.

In addition to its transparency range, fused quartz has other properties. Its low absorption in the IR range is due to the presence of oxygen and silicon. However, most commercial quartz glass contains other impurities such as aluminium, titanium, or even water during manufacturing processes. In addition, water used in manufacturing processes can embed hydroxyl groups, which decrease optical transmission in the infrared range.

Fused silica is an amorphous form of silicon dioxide. It exhibits good transmission in the ultraviolet, visible, and infrared regions and is less dispersed than cultured quartz. It also has low thermal expansion and is resistant to thermal shock. Further, it has a very low coefficient of thermal expansion and is thus suitable for optical windows. A major benefit of using fused silica is its low nonlinear index.

Optical Windows Durability

Optical Windows made from Fused Silica are considered to be durable. They offer high levels of transparency at the 180nm and 2.3 micron wavelengths. The material is also free of fluorescent defects and has excellent thermal shock and chemical resistance. These materials are also used in high-precision laser applications and multiphoton imaging systems. To ensure durability, COE Optics stocks both UV and IR Fused Silica Windows, including multilayer AR coatings.

Fused silica has excellent optical properties and is inexpensive compared to other quartz glass types. Because of its low impurity content, it is suitable for high-precision and transmission applications. JGS2 wafers are ideal for electronic sensors and protective barriers. The JGS2 grade is similar to Homosil 1 and 2, and Dynasil 1000, but larger pieces will contain bubbles. For high-precision applications, JGS1 is preferred.

When considering fused silica as an optical window material, it is important to consider the environment in which it will be used. Optical windows in harsh environments should be UV-graded, as this type of material is less sensitive to UV rays and is highly resistant to thermal shocks. For example, in a laboratory, UV-Fused Silica windows can be used in high-tech applications where temperature is an issue. This type of glass is also highly resistant to radiation and does not cause orientation problems.