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Optical Materials
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| BK 7 |
BK 7 is one of the most common borosilicate crown glasses used for visible and near infrared optics. Its high homogeneity, low bubble content, and straightforward manufacturability make it a good choice for transmissive optics. The transmission range for BK 7 is 380–2100 nm. It is not recommended for temperature sensitive applications, such as precision mirrors.
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| UV Grade Fused Silica |
UV Grade Fused Silica is synthetic amorphous silicon dioxide of extremely high purity. This non-crystalline, colorless silica glass combines a very low thermal expansion coefficient with good optical qualities, and excellent transmittance in the ultraviolet. Transmission and homogeneity exceed those of crystalline quartz without the problems of orientation and temperature instability inherent in the crystalline form. Fused silica is used for both transmissive and reflective optics, especially where high laser damage threshold is required.
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| CaF2 |
Calcium Fluoride is a cubic single crystal material grown using the vacuum Stockbarger Technique with good vacuum UV to infrared transmission. CaF2 has excellent UV transmission, down to 170 nm, and its non-birefringent properties make it ideal for deep UV transmissive optics. Material for IR use is grown using naturally mined fluorite, at much lower cost. CaF2 is sensitive to thermal shock, so care must be taken during handling.
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| MgF2 |
Magnesium Fluoride is a positive birefringent crystal grown using the vacuum Stockbarger Technique with good vacuum UV to infrared transmission. It is typically oriented with the c axis parallel to the optical axis to reduce birefringent effects. High vacuum UV transmission, down to 150 nm, and its proven use in fluorine environments make it ideal for lenses, windows, and polarizers for Excimer lasers. MgF2 is resistant to thermal and mechanical shock.
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| Crystal Quartz |
Crystal Quartz is a positive uniaxial birefringent single crystal grown using a hydrothermal process. It has good transmission from the vacuum UV to the near infrared. Due to its birefringent nature, crystal quartz is commonly used for wave plates.
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| Pyrex® |
Pyrex® is a borosilicate glass with a low coefficient of thermal expansion. It is mainly used for non-transmissive optics, such as mirrors, due to its low homogeneity and high bubble content.
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| Zerodur® |
Zerodur® is a glass ceramic material that has a coefficient of thermal expansion approaching zero, as well as excellent homogeneity of this coefficient throughout the entire piece. This makes Zerodur ideal for mirror substrates where extreme thermal stability is required. Zerodur should not be used for transmissive optics due to inclusions in the material.
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| Properties of Optical Materials |
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Abbe Number
vd |
Coefficient of Thermal Expansion
(10-6/°C) |
Conductivity
(W/m°C) |
Heat Capacity
(J/gm°C) |
Density at 25°C
(gm/cm3) |
Knoop Hardness
(kg/mm2) |
Young’s Modulus
(GPa) |
| BK 7 |
64.17 |
7.1 |
1.114 |
0.858 |
2.51 |
610 |
81.5 |
| SF 2 |
33.85 |
8.4 |
0.735 |
0.498 |
3.86 |
410 |
55 |
| UV Fused Silica |
67.8 |
0.52 |
1.38 |
0.75 |
2.202 |
600 |
73 |
| CaF2 |
94.96 |
18.85 |
9.71 |
0.85 |
3.18 |
158 |
75.8 |
| MgF2 |
106.18 |
13.7 || to c axis
8.48 ⊥ to c axis |
21 || to c axis
30 to ⊥ c axis |
1.024 |
3.177 |
415 |
138.5 |
| Crystal Quartz |
69.87 |
7.1 to || c axis
13.2 ⊥ to c axis |
10.4 || to c axis
6.2 ⊥ to c axis |
0.74 |
2.649 |
740 |
97 || to c axis
76.5 ⊥ to c axis |
| Pyrex® |
66 |
3.25 |
1.13 |
0.75 |
2.23 |
418 |
65.5 |
| Zerodur® |
56.09 |
0 ± 0.1 |
1.46 |
0.80 |
2.53 |
620 |
90.3 |
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| Index of Refraction |
Wavelength
(nm) |
Source |
BK 7 |
SF 2 |
UV Fused Silica |
CaF2 |
MgF2
no |
MgF2
ne |
Crystal Quartz
no |
Crystal Quartz
ne |
| 193 |
ArF excimer laser |
1.65528 |
1.52127 |
1.56077 |
1.50153 |
1.42767 |
1.44127 |
1.66091 |
1.67455 |
| 244 |
Ar-Ion laser |
1.58265 |
1.98102 |
1.51086 |
1.46957 |
1.40447 |
1.41735 |
1.60439 |
1.61562 |
| 248 |
KrF excimer |
1.57957 |
1.93639 |
1.50855 |
1.46803 |
1.40334 |
1.41618 |
1.60175 |
1.61289 |
| 257 |
Ar-Ion laser |
1.57336 |
1.86967 |
1.50383 |
1.46488 |
1.40102 |
1.41377 |
1.59637 |
1.60731 |
| 266 |
Nd:YAG laser |
1.56796 |
1.82737 |
1.49968 |
1.46209 |
1.39896 |
1.41164 |
1.59164 |
1.60242 |
| 308 |
XeCl excimer laser |
1.55006 |
1.73604 |
1.48564 |
1.45255 |
1.39188 |
1.40429 |
1.57556 |
1.58577 |
| 325 |
HeCd laser |
1.54505 |
1.71771 |
1.48164 |
1.44981 |
1.38983 |
1.40216 |
1.57097 |
1.58102 |
| 337.1 |
N2 laser |
1.54202 |
1.70749 |
1.47919 |
1.44813 |
1.38858 |
1.40085 |
1.56817 |
1.57812 |
| 351 |
XeF excimer laser |
1.53896 |
1.69778 |
1.47672 |
1.44642 |
1.38730 |
1.39952 |
1.56533 |
1.57518 |
| 351.1 |
Ar-Ion laser |
1.53894 |
1.69771 |
1.47671 |
1.44641 |
1.38729 |
1.39951 |
1.56531 |
1.57516 |
| 354.7 |
Nd:YAG laser |
1.53821 |
1.69548 |
1.47612 |
1.44601 |
1.38699 |
1.39920 |
1.56463 |
1.57446 |
| 363.8 |
Ar-Ion laser |
1.53649 |
1.69029 |
1.47472 |
1.44504 |
1.38626 |
1.39844 |
1.56302 |
1.57279 |
| 404.7 |
Mercury arc, h line |
1.53023 |
1.67263 |
1.46961 |
1.44151 |
1.38360 |
1.39567 |
1.55714 |
1.56670 |
| 416 |
Kr-Ion laser |
1.52885 |
1.66893 |
1.46847 |
1.44072 |
1.38301 |
1.39505 |
1.55583 |
1.56535 |
| 435.8 |
Mercury arc,g line |
1.52669 |
1.66331 |
1.46670 |
1.43949 |
1.38207 |
1.39408 |
1.55379 |
1.56323 |
| 441.6 |
HeCd laser |
1.52611 |
1.66184 |
1.46622 |
1.43916 |
1.38183 |
1.39382 |
1.55324 |
1.56266 |
| 457.9 |
Ar-Ion laser |
1.52461 |
1.65807 |
1.46498 |
1.43830 |
1.38118 |
1.39314 |
1.55181 |
1.56119 |
| 465.8 |
Ar-Ion laser |
1.52395 |
1.65641 |
1.46443 |
1.43792 |
1.38088 |
1.39284 |
1.55118 |
1.56053 |
| 472.7 |
Ar-Ion laser |
1.52339 |
1.65505 |
1.46397 |
1.43760 |
1.38064 |
1.39258 |
1.55065 |
1.55998 |
| 476.5 |
Ar-Ion laser |
1.52309 |
1.65432 |
1.46372 |
1.43744 |
1.38051 |
1.39245 |
1.55036 |
1.55969 |
| 480 |
Cadmium arc, F’ line |
1.52283 |
1.65367 |
1.46350 |
1.43728 |
1.38040 |
1.39233 |
1.55011 |
1.55943 |
| 486.1 |
Hydrogen arc, F line |
1.52238 |
1.65258 |
1.46313 |
1.43703 |
1.38020 |
1.39212 |
1.54968 |
1.55898 |
| 488 |
Ar-Ion laser |
1.52224 |
1.65225 |
1.46301 |
1.43695 |
1.38014 |
1.39206 |
1.54955 |
1.55885 |
| 496.5 |
Ar-Ion laser |
1.52165 |
1.65083 |
1.46252 |
1.43661 |
1.37988 |
1.39179 |
1.54898 |
1.55826 |
| 501.7 |
Ar-Ion laser |
1.52130 |
1.65000 |
1.46223 |
1.43641 |
1.37973 |
1.39163 |
1.54865 |
1.55792 |
| 510.6 |
Cu vapor laser |
1.52073 |
1.64865 |
1.46176 |
1.43609 |
1.37948 |
1.39137 |
1.54810 |
1.55735 |
| 514.5 |
Ar-Ion laser |
1.52049 |
1.64808 |
1.46156 |
1.43595 |
1.37937 |
1.39126 |
1.54787 |
1.55711 |
| 532 |
Nd:YAG laser |
1.51947 |
1.64570 |
1.46071 |
1.43537 |
1.37892 |
1.39079 |
1.54689 |
1.55610 |
| 543.5 |
HeNe laser |
1.51886 |
1.64427 |
1.46019 |
1.43502 |
1.37865 |
1.39051 |
1.54630 |
1.55549 |
| 546.1 |
Mercury arc, e line |
1.51872 |
1.64397 |
1.46008 |
1.43494 |
1.37859 |
1.39044 |
1.54617 |
1.55535 |
| 578.2 |
Cu vaport laser |
1.51720 |
1.64053 |
1.45880 |
1.43408 |
1.37792 |
1.38974 |
1.54470 |
1.55383 |
| 587.6 |
Helium arc, d line |
1.51680 |
1.63963 |
1.45846 |
1.43385 |
1.37774 |
1.38956 |
1.54431 |
1.55343 |
| 589.3 |
Sodium arc, D line |
1.51673 |
1.63947 |
1.45840 |
1.43381 |
1.37771 |
1.38952 |
1.54424 |
1.55336 |
| 594.1 |
HeNe laser |
1.51653 |
1.63904 |
1.45824 |
1.43370 |
1.37762 |
1.38943 |
1.54405 |
1.55316 |
| 611.9 |
HeNe laser |
1.51584 |
1.63752 |
1.45765 |
1.43331 |
1.37732 |
1.38911 |
1.54337 |
1.55247 |
| 628 |
Ruby laser |
1.51526 |
1.63626 |
1.45716 |
1.43298 |
1.37706 |
1.38884 |
1.54281 |
1.55188 |
| 632.8 |
HeNe laser |
1.51509 |
1.63590 |
1.45702 |
1.43289 |
1.37698 |
1.38876 |
1.54264 |
1.55171 |
| 635 |
Laser diode |
1.51501 |
1.63574 |
1.45695 |
1.43284 |
1.37695 |
1.38873 |
1.54257 |
1.55164 |
| 643.8 |
Cadmium arc, C' line |
1.51472 |
1.63512 |
1.45671 |
1.43268 |
1.37682 |
1.38859 |
1.54228 |
1.55134 |
| 647.1 |
Kr-Ion laser |
1.51461 |
1.63489 |
1.45661 |
1.43262 |
1.37677 |
1.38854 |
1.54218 |
1.55123 |
| 650 |
Laser diode |
1.51452 |
1.63469 |
1.45653 |
1.43257 |
1.37673 |
1.38850 |
1.54209 |
1.55114 |
| 656.3 |
Hydrogen arc, C line |
1.51432 |
1.63427 |
1.45637 |
1.43246 |
1.37664 |
1.38840 |
1.54189 |
1.55093 |
| 670 |
Laser diode |
1.51391 |
1.63340 |
1.45601 |
1.43223 |
1.37646 |
1.38821 |
1.54148 |
1.55051 |
| 676.4 |
Kr-Ion laser |
1.51372 |
1.63301 |
1.45585 |
1.43212 |
1.37637 |
1.38812 |
1.54130 |
1.55032 |
| 694.3 |
Ruby laser |
1.51322 |
1.63198 |
1.45542 |
1.43185 |
1.37615 |
1.38789 |
1.54080 |
1.54981 |
| 750 |
Laser diode |
1.51184 |
1.62922 |
1.45424 |
1.43109 |
1.37553 |
1.38724 |
1.53943 |
1.54839 |
| 780 |
Laser diode |
1.51118 |
1.62796 |
1.45367 |
1.43074 |
1.37524 |
1.38693 |
1.53878 |
1.54771 |
| 830 |
Laser diode |
1.51020 |
1.62613 |
1.45282 |
1.43023 |
1.37480 |
1.38647 |
1.53779 |
1.54668 |
| 850 |
Laser diode |
1.50984 |
1.62548 |
1.45250 |
1.43004 |
1.37464 |
1.38630 |
1.53742 |
1.54630 |
| 852.1 |
Cesium arc, s line |
1.50980 |
1.62541 |
1.45247 |
1.43002 |
1.37462 |
1.38628 |
1.53739 |
1.54626 |
| 905 |
Laser diode |
1.50892 |
1.62387 |
1.45168 |
1.42957 |
1.37422 |
1.38586 |
1.53648 |
1.54532 |
| 980 |
Laser diode |
1.50779 |
1.62202 |
1.45067 |
1.42902 |
1.37371 |
1.38533 |
1.53531 |
1.54409 |
| 1014 |
Mercury arc, t line |
1.50731 |
1.62128 |
1.45024 |
1.42879 |
1.37350 |
1.38510 |
1.53481 |
1.54357 |
| 1053 |
Nd:YLF laser |
1.50678 |
1.62049 |
1.44976 |
1.42854 |
1.37326 |
1.38485 |
1.53425 |
1.54299 |
| 1060 |
Nd:Glass laser |
1.50669 |
1.62035 |
1.44968 |
1.42850 |
1.37322 |
1.38480 |
1.53415 |
1.54288 |
| 1064 |
Nd:YAG laser |
1.50663 |
1.62028 |
1.44963 |
1.42848 |
1.37319 |
1.38478 |
1.53410 |
1.54282 |
| 1300 |
Laser diode |
1.50370 |
1.61644 |
1.44692 |
1.42721 |
1.37188 |
1.38338 |
1.53094 |
1.53950 |
| 1320 |
Nd:YAG laser |
1.50346 |
1.61616 |
1.44669 |
1.42711 |
1.37177 |
1.38327 |
1.53068 |
1.53922 |
| 1550 |
Laser diode |
1.50065 |
1.61312 |
1.44402 |
1.42602 |
1.37052 |
1.38194 |
1.52761 |
1.53596 |
| 1970.1 |
Mercury arc |
1.49495 |
1.60780 |
1.43852 |
1.42401 |
1.36803 |
1.37928 |
1.52138 |
1.52932 |
| 2100 |
Ho:YAG laser |
1.49296 |
1.60608 |
1.43659 |
1.42334 |
1.36718 |
1.37837 |
1.51924 |
1.52703 |
| 2325.4 |
Mercury arc |
1.48921 |
1.60291 |
1.43293 |
1.42212 |
1.36559 |
1.37667 |
1.51524 |
1.52277 |
| 2940 |
Er:YAG laser |
1.47670 |
1.59273 |
1.42065 |
1.41827 |
1.36051 |
1.37123 |
1.50246 |
1.50908 |
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| Transmittance of Optical Materials |
These graphs compare the transmission of standard optical materials. The transmission values listed here are equivalent to "external transmittance" and takes into consideration the reflectances you get from uncoated optical elements.
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Transmission of 10 mm thick fused silica, BK7, and crown glass windows.
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Transmittance of IR optical materials.
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Transmittance of UV-IR materials.
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Transmittance of VIS-NIR materials.
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| Reflectance of Optical Materials |
All metal reflectors deteriorate slowly in polluted atmosphere. Cumulative exposure to intense ultraviolet radiation also affects performance; overheating of the reflective surface will destroy the reflector.
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Typical near normal incidence reflectance of freshly deposited Al, AlMgF2, AlSiO, and Au.
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Typical near normal incidence reflectance of Rhodium, enhanced Rhodium, and Silver with Dielectric orvercoat.
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The enhanced rhodium coating has been optimized for high performance in the ultraviolet, a wide range of angles of incidence and longevity. It is the most efficient and durable coating available for ellipsoidal reflectors. The AlMgF2 coating has been optimized for performance in the near UV.
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