Quartz Glass for Optics
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Fused Quartz and Fused Silica are types of Quartz Glass containing primarily silica in amorphous form. They are manufactured using several different processes.
Fused Quartz is made by melting of high purity naturally occurring quartz crystals at around 2000°C using either an electrically heated furnace (electrically fused) or a gas/oxygen-fuelled furnace (flame fused). Fused Quartz is normally transparent.
Fused Silica is produced using high purity silica sand as the feedstock and is normally melted using an electric furnace, resulting in a material that is translucent or opaque. This opacity is caused by very small air bubbles trapped within the material.
Synthetic Fused Silica is made from a silicon-rich chemical precursor and there are two main grades of the material which are widely utilized for optical manufacturing:
- UV grade of synthetic FS (KU-1); produced by continuous high temperature hydrolysis of silicon tetrachloride - SiCl4 in hydrogen-oxygen flame;
- UV-IR grade of synthetic FS (KS-4V); produced by complex process which involves chemical gasification of silicon, oxidation of this gas to silicon dioxide (SiO2), and thermal fusion of the resulting ash in vacuum.
Both Synthetic Fused Silica grades are ultra pure, single component glasses with a unique combination of thermal, optical and mechanical properties, which make them the preferred materials for use in a variety of processes and applications where other materials are not suitable. The very high purity (over 99.9%) ensures minimum contamination in process applications. These materials can routinely withstand temperatures of over 950°C and due to their very low coefficient of thermal expansion can be rapidly heated and cooled with virtually no risk of breakage due to thermal shock. All this together with excellent transmission in compare with most other glasses make them useful materials for production of superior quality optical windows, lenses, prisms, beam-splitters, beam-combiners, cold/hot mirrors, et cetera, and so on. These materials are inert to most substances, including virtually all acids, allowing their use in rather severe environments. The dielectric properties and very high electrical receptivity of these materials over a wide range of temperatures together with their low thermal conductivity allow their use as an electrical and thermal insulating material in wide range of environments. The combination of thermal, chemical and UV stability together with high DUV transparency make them an excellent choice for projection masks for photolythography.
Tydex produces wide range of optical components from UV-FS and UV-IR FS so please link the following chapters to get more detailed information:
Optics for Spectroscopy:
UV-FS (KU-1) features high transparency within ultraviolet and visible regions. It has no absorption bands within 170-250 nm wavelength interval. It has an intensive OH-absorption band at 2600-2800nm wavelength range. This grade does not express fluorescence as a result of UV excitation and is characterized by optical-radiation stability. It is practically free from bubbles and inclusions.
The nearest analogues of quartz glass KU-1 are:
Suprasil Standard (Heraeus), Spectrosil A and B (Saint-Gobain), Corning 7940 (Corning), Dynasil 1100 and 4100 (Dynasil).
UV-IR FS (KS-4V) combines excellent physical properties with outstanding optical characteristics from DUV (through VISible) up to middle IR wavelength range and is the preferred material for transmission optics over this wide spectral diapason. It has no absorption bands within 170-250 nm wavelength range as well as no OH-absorption at around 2700 nm. It is practically free from bubbles and inclusions.
At near IR range the nearest analogue of quartz glass KS-4V is Infrasil (Heraeus).
Below is comparative and summarizing table of the properties of these two grades of synthetic fused silica.
Main Properties
| Parameter Value | Grade of Synthetic Fused Silica | |||||||||||||||||||||||||
| KU-1 | KS-4V | |||||||||||||||||||||||||
| Max. available diameter of the material, mm | melted blocks of D220x200 mm-thick | - melted blocks of D260x400 mm-thick; - molded blocks of D320x10 mm-thick. |
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| The edges of transmission range, nm | 160-4350 | 150-4350 | ||||||||||||||||||||||||
| Transmission range where an average transmission bigger 90%, nm | 180-2100 | 190-3500 | ||||||||||||||||||||||||
| UV transmission vs wavelength for 10mm-thick sample | 170nm - above 65% 180nm - 80% 190nm - 86% |
170nm - above 50% 180nm - 78% 190nm - 83% |
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| OH-content, ppm | < 2000 | < 0.1 | ||||||||||||||||||||||||
| Fluorescence (after UV excitation) | none | none | ||||||||||||||||||||||||
| Total metallic impurities, ppm | < 5 | < 0.1 | ||||||||||||||||||||||||
| Birefringence constant, nm/cm | < 5 | < 10 | ||||||||||||||||||||||||
| Melting method | continuous high temperature hydrolysis of silicon tetrachloride in hydrogen-oxygen flame | melting of silicon dioxide and thermal fusion of the resulting ash in vacuum | ||||||||||||||||||||||||
| Annealing point, °C | 1120 | 1250 | ||||||||||||||||||||||||
| Softening point, °C | 1600 | 1750 | ||||||||||||||||||||||||
| Optical-radiation stability (Co60 gamma-irradiation (1.15 MeV)) |
stable | stable up to 11 MGray doze | ||||||||||||||||||||||||
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Identical Properties of Both Grades
| Density, g/cm3 | 2.21 |
| Refractive index | nF (486nm) = 1.4631 nd (588nm) = 1.4585 nC (656nm) = 1.4564 |
| Abbe constant | 67.8 |
| Thermal coefficient of linear expansion at the temperature range 20-1000°C, °C-1 | 0.55 x 10-6 |
| Knoop hardness, kg/mm2 | 500 |
| Poisson ratio, (T = 25°C) | 0.17 |
| Bulk modulus, GPa (T = 25°C) | 36.9 |
| Tensile strength, MPa | 50 |
| Compressive strength, GPa | 1.1 |
| Young's modulus, GPa (T = 25°C) | 73 |
| Rupture modulus, MPa (T = 25°C) | 50 |
| Shear modulus, GPa (T = 25°C) | 31 |
| Strain point, °C | 1025 |
| Max. service temperature, °C | 950 – continuous, 1200 – limited period |
| Dielectric strength, kV/cm | 250-400 |
| Thermal conductivity, W/(m x K) (T = 25°C) |
1.38 |
| Specific heat capacity, J/(kg x K) (T = 25°C) |
728 |
| Chemical stability | High resistance to water and acids (except hydrofluoric) |
Synthetic Fused Silica refractive index vs wavelength (for KU-1 is valid up to 2µm)
| Wavelength, µm | Refractive Index | Wavelength, µm | Refractive Index |
| 0.2 | 1.551 | 1.0 | 1.450 |
| 0.22 | 1.528 | 1.1 | 1.450 |
| 0.25 | 1.507 | 1.2 | 1.448 |
| 0.3 | 1.488 | 1.3 | 1.447 |
| 0.32 | 1.483 | 1.5 | 1.445 |
| 0.36 | 1.475 | 1.6 | 1.443 |
| 0.4 | 1.470 | 1.7 | 1.442 |
| 0.45 | 1.466 | 1.8 | 1.441 |
| 0.5 | 1.462 | 1.9 | 1.440 |
| 0.55 | 1.460 | 2.0 | 1.438 |
| 0.60 | 1.458 | 2.2 | 1.435 |
| 0.65 | 1.457 | 2.4 | 1.431 |
| 0.7 | 1.455 | 2.6 | 1.428 |
| 0.75 | 1.454 | 2.8 | 1.424 |
| 0.8 | 1.453 | 3.0 | 1.419 |
| 0.85 | 1.452 | 3.2 | 1.414 |
| 0.9 | 1.452 | 3.37 | 1.410 |
Tydex can process these materials well into 20/10 scr/dig (MIL-0-13830A) and lambda/10 @ 632 nm (TWD and surface accuracy). Such standard catalogue parts (D12.7mm and D25.4 mm) are available from our stock.
Typical transmission curves (Fresnel reflection losses included) are shown at Figures 1 and Figure 2.
Figure 1. KU-1 and KS-4V transmission at 150-1000 nm.
Samples thickness is 10 mm.
Figure 2. KU-1 and KS-4V transmission at 1000-5000 nm.
Samples thickness is 10 mm.
Please pay attention that this article is only for your information. We do supply neither KU-1 nor
KS-4V in blanks or as raw materials. Our standard products are finished (polished, coated) parts.
For price quotation and delivery please fill in our request form.
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