OPTICAL SUBSTRATES OVERVIEW
There are likely numerous optical materials that can be used for your application. To find the best one for your application, you’ll need to consider the materials’ optical, mechanical, and chemical properties.
We’ve divided all the optical materials into material categories. Each material within a category, although similar to the others, will have its own optical properties, pricing, and availability.
Optical Substrate Data Sheets
Based on customer demand, we offer custom optical components made from the following substrate materials.
Color Filter Glass
Colored filter glass is available in a range of spectral characteristics each suited to unique transmission and absorption properties of various wavelengths of light.
- SCHOTT GG395
- SCHOTT GG400
- SCHOTT GG420
- SCHOTT GG435
- SCHOTT GG455
- SCHOTT GG475
- SCHOTT GG495
- SCHOTT N-WG280
- SCHOTT N-WG295
- SCHOTT N-WG305
- SCHOTT N-WG320
- SCHOTT OG515
- SCHOTT OG530
- SCHOTT OG550
- SCHOTT OG570
- SCHOTT OG590
- SCHOTT RG1000
- SCHOTT RG610
- SCHOTT RG630
- SCHOTT RG645
- SCHOTT RG665
- SCHOTT RG695
- SCHOTT RG715
- SCHOTT RG780
- SCHOTT RG830
- SCHOTT RG850
- SCHOTT RG9
Optical crystals are glass-like materials grown from high-purity raw materials. The most common crystals include calcium fluoride—effective for UV-spectrum applications—and magnesium fluoride, which is useful for mid-wave IR applications.Popular Materials
Display GlassBorosilicate glass, also called display glass, offers a combination of excellent light transmission and impressive technical properties. Made of silicon oxide and boron oxide, display glass is easily laser- or CNC-machined. In addition to having excellent chemical resistance, the material possesses a low coefficient of thermal expansion, meaning that it can resist high temperatures without cracking.
- Corning EAGLE XG
- Pilkington Optiwhite
- SCHOTT B 270 i Ultra-White Glass
- SCHOTT BOROFLOAT 33
- SCHOTT D 263 T eco
- SCHOTT OPALIKA
- SCHOTT SUPREMAX 33
Fused QuartzFused Quartz is made using high quality, natural quartz powders with several fusion methods. Quartz material is stronger than glass, can be used at high temperatures (<1050°C) and has a high average transmission of over 80% from 260nm to 2500nm. The various qualities of fused quartz allow for use in a wide range of applications from semiconductor applications to lower precision window applications in hostile environments.
- Heraeus HOQ 310
- Heraeus INFRASIL 301, 302
- Heraeus TSC Series
- Momentive i21 (Previously GE 124)
- Ohara SK-4304, SK-4306
- Tosoh N, OP, S Series
Fused SilicaFused silica is a transparent glass formed by melting and cooling pure silica sand. Unlike most other glasses, fused silica does not contain any additives. It is an amorphous solid with a purity that gives it excellent optical transmission.
- Corning HPFS 7979 (UV & IR Grades)
- Corning HPFS 7980 (ArF Grade)
- Corning HPFS 7980 (Industrial Grade)
- Corning HPFS 7980 (KrF Grade)
- Corning HPFS 7980 (Standard Grade)
- Corning HPFS 8655
- Heraeus HOMOSIL 101, HERASIL 102
- Heraeus SUPRASIL 1, 2 (Grade A & B)
- Heraeus SUPRASIL 3001, 3002
- Heraeus SUPRASIL 311, 312
- Heraeus SUPRASIL 313
- Nikon NIFS (V, A, U, S Grade)
- Ohara SK-1300
- Ohara SK-1310
- Ohara SK-1320
- Tosoh ES, ED-H Series
Infrared materials produce good transmission in the infrared (IR) spectrum, which spans 0.75 μm to 15µm. Infrared materials are commonly selected for their transmission properties in the NIR (0.75µm – 1µm), SWIR (1µm – 2.7µm), MWIR (3µm – 5µm) or LWIR (8µm – 12µm) spectral sub-regions. The most common IR materials are silicon, germanium, sapphire, zinc sulfide, and zinc selenide.
- Zinc Selenide
Low ExpansionLow expansion glass-ceramics are characterized by a near-zero coefficient of thermal expansion and excellent resistance to thermal shock. These materials have high purity and chemical stability, with minimal internal stress.Popular Materials
Optical GlassOptical glass is known for its high transmission, low dispersion, and homogenous refraction indices. These properties result from the continuous melting process and subsequent finishing methods used to create optical glass. This material is categorized into either flint glass or crown glass. Flint glass has an Abbe number < 55 and generally < 50. Flint glass is denser due to the inclusion of various metal oxides and exhibits strong chromatic dispersion. Crown glass has an Abbe number> 50 and generally > 55. Crown glass is typically less dense resulting from higher usage of alkali metals and exhibits low chromatic dispersion.
- Hoya BSC7
- Ohara S-BSL 7
- Ohara S-TIH1
- Ohara S-TIH10
- Ohara S-TIH11
- Ohara S-TIH4
- Ohara S-TIH6
- Ohara S-TIM22
- Ohara S-TIM25
- Ohara S-TIM28
- SCHOTT BK7G18
- SCHOTT N-BK7
- SCHOTT N-BK7HT
- SCHOTT N-SF1
- SCHOTT N-SF10
- SCHOTT N-SF11
- SCHOTT N-SF2
- SCHOTT N-SF4
- SCHOTT N-SF5
- SCHOTT N-SF6
- SCHOTT N-SF8
Material Category Properties
Optical properties refer to how the material behaves with light.
The two most prominent optical properties for glass materials are the index of refraction and the Abbe number.
Index of Refraction
The index of refraction is the ratio of the velocity of light in a vacuum to the velocity of light in a refractive material for a given wavelength.
For example, light will travel through materials with a lower index of refraction quicker than materials with a high index of refraction because the higher refraction will bend light more.
The Abbe number quantifies the amount of dispersion in a given spectral range. For example, a low Abbe number gives higher color dispersion while a high Abbe number reduces color aberration.
The mechanical and thermal properties of optical materials indicate how the glass will perform under certain conditions and in certain environments.
The hardness and grindability of a material determine how it is processed in order to achieve good polishing quality whereas the density influences the weight of the final component.
The thermal properties of optical materials determine how the material reacts in varying temperatures. This is important because optical materials are often used in environments with extreme temperatures and IR applications often produce a lot of heat.
The most important property to evaluate when choosing your optical material is the coefficient of thermal expansion; however, the thermal conductivity and the index gradient are also key indicators of how a material will act in an application.
The coefficient of thermal expansion refers to the rate at which the material expands or contracts at any given temperature. When interpreting material data sheets, the coefficient of thermal expansion in the temperature range between – 30°C und + 70°C in 10-6/K is denoted as: (α -30/+70).
Bubbles that originate from non-perfect refining processes are referred to as residual bubbles. Gaseous bubbles are often created by the melting process and are usually unavoidable.
Bubbles are categorized based on bubble size and concentration in a defined space.
Optical glass is generally free of bubbles, but they cannot be completely avoided.
Bubbles in optical material may cause light scattering and loss of transmission due to absorption. In most optical systems, inclusions do not create significant problems, but for some systems, the presence and size of bubbles can be an issue. Applications such as high energy lasers, beamsplitter prisms, and high pitch gratings must be made with glasses that have a minimal number of bubbles.
The Knoop hardness test is used to determine how resistant a glass material is to indentation. It is the standard test used to measure a material’s hardness. In the material data sheets, Knoop hardness can be denoted as HK.
The formula used to determine this property is:
HK = 14.229(F/D2)
In this equation, F stands for the applied load measured in kilograms-force, and D2 stands for the area of the indentation measured in square millimeters.
Knoop hardness can also affect a glass supplier’s ability to get better cosmetics and affect the time it takes to polish and grind the glass.
The homogeneity of a material indicates how well the material was melted together to combine the different parts that make up the glass. The better the particles are mixed together, the more likely the material is to transmit a wavefront accurately. Therefore, better homogeneity is required for tighter transmitted wavefront requirements.
Chemical properties of a glass determine how the glass holds up against water, moisture, acids, and alkalis. There is not a definitive way to measure and assess the chemical properties of optical glass, so the tests and units of measurement for chemical properties differ depending on the optical glass manufacturer you choose.
The five resistance tests that have been internationally standardized across the industry are:
- Acid resistance test SR
- Alkali resistance test AR
- Phosphate resistance PR
- Climate resistance CR
- Stain resistance FR
When it comes to environmental influences and chemical demands, there is a wide range of resistance among different glasses. What’s more, one test cannot adequately describe the chemical behavior of all kinds of optical materials. In order to choose the right glass for your application, you must consider the results of several tests.
Acid resistance describes the behavior of the glass when it comes in contact with larger quantities of acidic solutions. This is measured by the precision removal of a very thin layer of glass when exposed to acid. This can involve testing with both weak and strong acids depending on the acid resistance of the glass types.
Alkali resistance describes the sensitivity of the material when in contact with warm, alkali liquids. This is measured by the precision removal of a very thin layer of glass using alkali. This is important for the manufacturer making the optics as it could affect the performance of the grinding and polishing processes.
Phosphate resistance describes the sensitivity of the material when in contact with washing solutions that contain phosphates. This is measured by the precision removal of a very thin layer of glass using phosphates.
Climate resistance describes how the glass behaves in environments with high relative humidity and high temperatures. High levels of water vapor in the air, especially at high temperatures, can cause a cloudy film to build on the glass surface that generally can’t be wiped off, which is a chemical reaction with water in deficiency.
Stain resistance does not refer to resistance on climatic change (see above) or highly acidic solutions, but provides information about possible changes in the glass surface, or stain formation, in acidic water without vaporization. Stain resistance class FR0 contains glass that shows virtually no stains after 100 hours of exposure in Sodium Acetate Buffer pH 4.6.
There are some glasses that do not form stains, but have low acid and climatic resistance. In these types of glass, layers of the glass can be removed during testing without stain formation.