Technical Reference : Characteristic of Glass Materials
The glass materials used by Sigma Koki can be roughly classified into one of two groups, depending on their intended use: glass for total reflection and glass for transmission. Since optical materials for total reflection applications use only their surfaces and do not demand special materials, they are selected for convenience in polishing and thermal stability of the polished surfaces. In contrast, optical materials for light transmission applications use both the surfaces and the interior, making characteristics such as transmittance, homogeneity, and presence or absence of internal bubbles important, in addition to properties of total reflectance glass material. The refractive index of glass is a major consideration for lenses that refract light, while both light dispersion and refractive index are important for prisms and combination lenses. Glass for light transmission applications is carefully selected from several hundreds types of optical glass, after considering optical characteristics, as wel l as characteristics such as cost and chemical and physical properties.
Typically of higher quality than ordinary glass, optical glass has specific refractive indices and must meet certain requirements for striae, bubbles, and other characteristics.
BK7 Symbol "B"
Features
BK7 is a borosilicate optical glass.
Used as substrates for small sized mirrors and transmissive optics.
Chemically stable and surfaces not easily tarnished.
Relatively hard compared to other optical glasses and prevent scratches.
Highly homogeneous with a low bubble and inclusion count.
High transmittance through the wavelength range of 350 to 2000nm.
Inexpensive and readily available due to the mass production.
Synthetic Fused Silica Symbol "SFS"
Features
An optical material, which commonly used in UV region.
Has extremely low thermal expansion (1/10 of BK7), making it an ideal substrate material for high precision mirrors.
Due to the manufacturing process, fused silica contains hydroxyls and therefore contains absorption bands at 1.38μm, 2.22μm, 2.72μm.
High UV and visible transmission.
Highly homogeneous with a low bubble and inclusion count.
Usable through broad temperature ranges in excess of 800°C.
Low fluorescence in UV.
Very hard and difficult to scratch making it easy to clean.
Water Free Fused Silica Symbol "NQ"
Features
Plasma manufacturing method produces less absorption through the IR region preventing the generation of hydroxyls.
Relatively expensive material due to the large electric consumption during manufacturing.
Suitable to use as a substrate for transmissive optics.
Pyrex® Symbol "PX"
Features
Similar to BK7, Pyrex® is classified as a borosilicate glass and common for scientific use.
Has relatively low thermal expansion (1/2 of BK7) and therefore used as a medium sized mirror substrate.
Since Pyrex® is not an optical glass, it often contains bubbles, impurities and striae (inhomogeneity).
Easy to polish and difficult to scratch making it easy to handle and clean.
B270-SUPERWHITE (White Glass)
Inexpensive and high transparent crown glass with a transmittance is similar to BK7.
Readily available making it easy to procure.
White glass is suitable for low precision optics only.
Other Optical Glasses / Specialty Glasses
High refractive index glass LaSFN9, and medium refractive index glass SK2 are both used as the material of lenses because of its excellent chemical and mechanical characteristics for fabrication.
Excimer Laser Grade Synthetic Fused Silica Symbol "SFSK"
Excimer laser grade fused silica is produced by controlling the amount of hydroxyls contained inside fused silica, and therefore shows high durability when irradiated by excimer laser light.
Sigma Koki manufactures standard catalog lenses using excimer laser grade fused silica. Parts are normally made by fused silica, which is suitable for use with 248nm excimer lasers. Please ask to our sales when using with 193nm excimer lasers.
When optical glass is irradiated by strong UV light, transmittance falloff or color center formation will occur and therefore periodical replacement of the optics is required.
| Irradiating Laser | Intensity | Repetition | Irradiating Time | Inspection Standard | |
|---|---|---|---|---|---|
| Ar*F(193nm) Grade Synthetic Fused Silica | Ar*F Excimer Laser | 10mJ/cm2 | 100Hz | 17min | No Fluorescence |
| Kr*F(248nm)Grade Synthetic Fused Silica | Kr*F Excimer Laser | 50mJ/cm2 | 25Hz | 2min | No Fluorescence |
Characteristics of Optical Glass
| Wavelength (nm) | BK7 | SK2 | LaSFN9 | |
|---|---|---|---|---|
| Refractive Index | 334.1 | 1.54272 | 1.64304 | - |
| 365.1 | 1.53627 | 1.63398 | - | |
| 404.7 | 1.53024 | 1.62562 | 1.89844 | |
| 480 | 1.52283 | 1.61547 | 1.87059 | |
| 546.1 | 1.51872 | 1.60994 | 1.85651 | |
| 587.6 | 1.5168 | 1.60738 | 1.85025 | |
| 632.8 | 1.51509 | 1.60513 | 1.84489 | |
| 706.5 | 1.51289 | 1.6023 | 1.83834 | |
| 852.1 | 1.5098 | 1.59847 | 1.82997 | |
| 1060 | 1.50669 | 1.5949 | 1.82293 | |
| 1529.6 | 1.50091 | 1.58914 | 1.81363 | |
| 1970.1 | 1.49495 | 1.58378 | 1.80657 | |
| 2325.4 | 1.48921 | 1.57881 | 1.80055 | |
| Density (g/cm3) | 2.51 | 3.55 | 4.44 | |
| Thermal Expansion Coefficient (x10-6) | 7.1(-30 to 70°C) | 6.0(-30 to 70°C) | 7.4(-30 to 70°C) | |
| Thermal Conductivity (W/m / K) | 1.114 | 0.776 | - | |
Extracted from SHOTT catalog.
Characteristics of Glass Materials
| Wavelength (nm) | Synthetic Fused Silica | Pyrex® | B270-SUPERWHITE | |
|---|---|---|---|---|
| Refractive Index | 193 | 1.561 | - | - |
| 200 | 1.548 | - | - | |
| 300 | 1.486 | - | - | |
| 350 | 1.476 | 1.48 | - | |
| 400 | 1.47 | 1.478 | - | |
| 500 | 1.462 | 1.474 | 1.5251(546nm) | |
| 600 | 1.458 | 1.472 | 1.5230(588nm) | |
| 700 | 1.455 | - | - | |
| 800 | 1.453 | - | - | |
| 1000 | 1.451 | - | - | |
| 1500 | 1.445 | - | - | |
| 2000 | 1.438 | - | - | |
| 2500 | 1.43 | - | - | |
| 3000 | 1.419 | - | - | |
| 3500 | 1.407 | - | - | |
| Transmissive Range (μm) | 0.19 to 3.5 | 0.38 to 2.3 | 0.35 to 2.5 | |
| Reflection Loss (per surface at 500nm) | 3.50% | 3.7% | 4.30% | |
| Density (g/cm3) | 2.2 | 2.23 | 2.55 | |
| Thermal Expansion Coefficient (x10-6) | 0.55 | 3.25(20 to 300°C) | 9.4(20 to 300°C) | |
Optical Characteristic of BK7 and Synthetic Fused Silica (Reference Data)
Transmittance
Refractive index
Refractive Index (n) & Transmittance (T)
| Wavelength (nm) | Synthetic Fused Silica | BK7 | Light Sources | Mark | Spectral Region | ||
|---|---|---|---|---|---|---|---|
| n | T(%) | n | T(%) | ||||
| 165 | VUV | ||||||
| 166 | 0 | VUV | |||||
| 167 | 20 | VUV | |||||
| 168 | 35 | VUV | |||||
| 169 | 46 | VUV | |||||
| 170 | 50 | VUV | |||||
| 173 | 75 | VUV | |||||
| 175 | 80 | VUV | |||||
| 180 | 84 | VUV | |||||
| 185.4 | 85 | VUV | |||||
| 190 | 86 | VUV | |||||
| 193.5 | 1.561 | 87 | VUV | ||||
| 200 | 1.548 | 88 | UV | ||||
| 210 | 1.54 | 90 | UV | ||||
| 220 | 1.534 | 91 | UV | ||||
| 230 | 1.523 | 91 | UV | ||||
| 240 | 1.515 | 92 | UV | ||||
| 250 | 1.509 | 92 | UV | ||||
| 260 | 1.502 | 92 | UV | ||||
| 270 | 1.497 | 92 | UV | ||||
| 280 | 1.493 | 92 | UV | ||||
| 290 | 1.489 | 92 | 0 | UV | |||
| 300 | 1.486 | 92 | 15 | UV | |||
| 313.2 | 1.484 | 92 | 1.548 | 38 | UV | ||
| 325 | 1.483 | 92 | 1.545 | 58 | He-Cd laser | UV | |
| 334.2 | 1.48 | 93 | 1.543 | 72 | UV | ||
| 337.1 | 1.48 | 93 | 1.541 | 76 | N2laser | UV | |
| 351.1 | 1.476 | 93 | 1.539 | 85 | Ar laser | UV | |
| 355 | 1.476 | 93 | 1.539 | 88 | YAG(3) | UV | |
| 363.8 | 1.475 | 93 | 1.536 | 90 | Ar laser | UV | |
| 365 | 1.475 | 93 | 1.536 | 90 | Hg | i | UV |
| 398.8 | 1.47 | 93 | 1.531 | 90 | violet | ||
| 404.7 | 1.47 | 93 | 1.53 | 92 | Hg | h | violet |
| 435.8 | 1.467 | 93 | 1.527 | 92 | Hg | g | blue |
| 441.6 | 1.466 | 93 | 1.526 | 92 | He-Cd laser | blue | |
| 457.9 | 1.465 | 93 | 1.525 | 92 | Ar laser | blue | |
| 465.8 | 1.464 | 93 | 1.524 | 92 | Ar laser | blue | |
| 472.7 | 1.464 | 93 | 1.523 | 92 | Ar laser | blue | |
| 476.5 | 1.464 | 93 | 1.523 | 92 | Ar laser | blue | |
| 480 | 1.464 | 93 | 1.523 | 92 | Cd | F' | blue |
| 486.1 | 1.463 | 93 | 1.522 | 92 | H | F | blue |
| 488 | 1.463 | 93 | 1.522 | 92 | Ar laser | blue | |
| 496.5 | 1.462 | 93 | 1.522 | 92 | Ar laser | green | |
| 501.7 | 1.462 | 93 | 1.521 | 92 | Ar laser | green | |
| 514.5 | 1.461 | 93 | 1.52 | 92 | Ar laser | green | |
| 532 | 1.461 | 93 | 1.519 | 92 | YAG(2) | green | |
| 546.1 | 1.46 | 93 | 1.519 | 92 | Hg | e | green |
| 587.6 | 1.458 | 93 | 1.517 | 92 | He | d | yellow |
| 589.3 | 1.458 | 93 | 1.517 | 92 | Na | D | orange |
| 632.8 | 1.457 | 94 | 1.515 | 92 | He-Ne laser | red | |
| 643.9 | 1.457 | 94 | 1.515 | 92 | Cd | C' | red |
| 656.3 | 1.456 | 94 | 1.514 | 92 | H | C | red |
| 694.3 | 1.456 | 94 | 1.513 | 92 | RUBY laser | red | |
| 706.5 | 1.455 | 94 | 1.513 | 92 | He | r | red |
| 830 | 1.452 | 94 | 1.51 | 92 | GaAIAs | NIR | |
| 852.1 | 1.452 | 94 | 1.51 | 92 | Cs | s | NIR |
| 904 | 1.452 | 94 | 1.509 | 92 | GaAs laser | NIR | |
| 1014 | 1.45 | 94 | 1.508 | 92 | Hg | t | NIR |
| 1064 | 1.449 | 94 | 1.507 | 92 | YAG laser | NIR | |
| 1100 | 1.449 | 94 | 1.507 | 92 | NIR | ||
| 1200 | 1.448 | 93 | 1.505 | 92 | NIR | ||
| 1300 | 1.447 | 93 | 1.504 | 92 | NIR | ||
| 1350 | 1.447 | 91 | 1.504 | 92 | NIR | ||
| 1380 | 1.446 | 83 | 1.503 | 88 | NIR | ||
| 1400 | 1.446 | 87 | 1.503 | 91 | NIR | ||
| 1500 | 1.445 | 93 | 1.501 | 91 | NIR | ||
| 1600 | 1.443 | 94 | 1.5 | 91 | NIR | ||
| 1700 | 1.442 | 94 | 1.499 | 91 | NIR | ||
| 1800 | 1.441 | 94 | 1.497 | 88 | NIR | ||
| 1900 | 1.44.0 | 94 | 1.497 | 85 | NIR | ||
| 2000 | 1.438 | 94 | 1.495 | 83 | NIR | ||
| 2100 | 1.437 | 92 | 1.493 | 81 | NIR | ||
| 2200 | 1.435 | 67 | 1.492 | 73 | NIR | ||
| 2220 | 1.434 | 56 | 1.492 | 71 | NIR | ||
| 2250 | 1.434 | 64 | 1.491 | 70 | NIR | ||
| 2300 | 1.433 | 80 | 1.49 | 72 | NIR | ||
| 2400 | 1.431 | 87 | 1.487 | 65 | NIR | ||
| 2500 | 1.43.0 | 73 | 1.485 | 59 | MIR | ||
| 2600 | 1.428 | 58 | 1.484 | 55 | MIR | ||
| 2650 | 1.427 | 20 | 1.483 | 40 | MIR | ||
| 2700 | 1.426 | 0 | 1.483 | 30 | MIR | ||
| 2720 | 1.426 | 0 | 1.482 | 23 | MIR | ||
| 2750 | 1.425 | 0 | 1.481 | 19 | MIR | ||
| 2800 | 1.424 | 0 | 9 | MIR | |||
| 2900 | 1.422 | 40 | 0 | MIR | |||
| 3000 | 1.419 | 65 | MIR | ||||
| 3100 | 1.417 | 75 | MIR | ||||
| 3200 | 1.414 | 78 | MIR | ||||
| 3300 | 1.412 | 81 | MIR | ||||
| 3400 | 1.409 | 80 | MIR | ||||
| 3500 | 1.407 | 70 | MIR | ||||
| 3600 | 61 | MIR | |||||
| 3700 | 50 | MIR | |||||
| 3800 | 25 | MIR | |||||
| 3900 | 21 | MIR | |||||
| 4000 | 23 | MIR | |||||
| 4100 | 15 | MIR | |||||
| 4200 | 4 | MIR | |||||
| 4300 | 0 | MIR | |||||
ZERODUR® (Reference data)
Features
A crystallized glass manufactured by SHOTT GLAS (Germany). Once melted at high temperature and then subjected to heat treatment in which the glass undergoes a crystalline growth stage.
Optical Property etc.
| Transmissive Range | 0.4 to 2.5μm |
|---|---|
| Refractive Index | 486.1 nm 1.5491 |
| 587.6 nm 1.5424 | |
| 656.3 nm 1.5394 | |
| Surface Reflection Loss | 4.6% per surface (at 587.6 nm) |
| Specific Gravity | 2.53 |
| Average Thermal Expansion Coefficient | 0±0.10×10－6/K (0 to 50°C) |
ZERODUR®is registered trademark of SHOTT GLAS.
Thermal Expansion Ratio
Transmittance
CLEARCERAM®-Z (Reference data)
Features
CLEARCERAM®-Z is a crystallized glass developed by OHARA INC. and has an extremely low thermal expansion and high transparency.
A material which shows excellent characteristics in heat-resistance, hardness, mechanical strength, chemical durability and processability.
Optical Property etc.
| Transmissive Range | 0.4 to 2.5μm |
|---|---|
| Refractive Index | 587.6nm 1.546 |
| Surface Reflection Loss | 4.6% per surface (at 587.6 nm) |
| Specific Gravity | 2.55 |
| Thermal Expansion Coefficient | 0.0±1.0×10－7/°C |
| Degasification Analysis | No detection of metallic element (30°C to 1000°C) |
CLEARCERAM®is registered trademark of OHARA INC.
Thermal Expansion Ratio
