OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 18-1 Materials Section 18 Optical Materials OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 18-2 relative to air instead of vacuum. m2.8 m2.2 m2.5 m2.4 m3.4 m4.0 @ 5 @ 10 Some common indices: vacuumheliumhydrogenairwaterfused silicaplasticsglassborosilicate crown crown glasslight flint glassdense barium crowndense flint 1.0 diamondZnSe 1.000036 1.000132 1.51 1.46 1.000293 1.33 1.62 1.48-1.6 @ 0.5 1.57 1.52 1.72 2.4 ZnSSiliconGermaniumThe index of refraction is usually quoted 1 @ 13 @ @ 10 Index of Refraction OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 18-3 Absorption Band the curve is used in the visible. The index the curve is used in the visible. h. The index increases at the absorption h. rption bands occurs in the ultraviolet and een the absorption bands index decreases een ) n( one occurs in the infrared. The normal part of The occurs in the infrared. one is higher than the index for for blue wavelengths red wavelengths. Optical materials –of the abso one Generally bands. This is anomalous dispersion. Betw This is anomalous bands. with wavelength. The refractive index is a function of wavelengt Dispersion OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 18-4 N-FK51 N-SF6 N-LaK8 N-F2 N-BK7 N-LaSF31 m) Wavelength ( Wavelength 0.3 0.4 0.5 0.6 0.7 0.8 0.9
2.0 1.9 1.8 1.7 1.6 1.5 1.4 Index Different Materials OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 18-5 0 dn d Fd (H)C (He) (H) 486.1 nm I 587.6 nm h 656.3 nm (Hg)F' (Hg)g (Cd) 365.0 nm e 404.7 nm (Hg)D 480.0 nm (Hg)C' (Na) 435.8 nm r (Cd) 546.1 nm t 589.3 nm (He) 643.8 nm (Hg) 706.5 nm 1014.0 nm Dispersion: - FC nn dispersion) to 1.5% (high of the nd reported at the specific wavelengths of spectrum, the dispersion of the index of spectrum, the dispersion of index - dC 1 nn C dC FC d nn nn n d - d n1 F Refractivity: Principal Dispersion: Partial Dispersion 1 n elemental spectral lines. Over the visible the elemental spectral lines. Over (low 0.5% refraction for optical glass is about mean value of the index. Index of refraction is commonly measured a measured of refraction is commonly Index Dispersion Curves OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 18-6 -values . C < 0.5. P-values can also be defined for -n is the single number used to characterize used single number is the Refractivity d d,C ves the fraction of the total index change ves the fraction of total index change rincipal dispersion P optical glass range from 25 to 65. Low 1 Y dC FC nn nn d FC n nn X FC nn nn , dC V , XY PP
P Due to the flattening P of the dispersion curve, Due indicate high dispersion. indicate high Relative partial dispersion ratio or P-value gi that occurs between the d and C wavelengths n the dispersion of the index of an optical material: the dispersion of index number for Typical values of the Abbe Abbe number (or reciprocal relative dispersion) other sets of wavelengths: other sets of wavelengths: Abbe Number OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 18-7 d n 1.90 1.80 1.70 1.60 1.50 20 Dispersion SF6 SF2 30 Polystyrene LaSF46 Polycarbonate Flint Glass F2 40 KzFS5 LLF1 LaSF31 KzFS4 50 LaF21 increases to the right. The glass line is the increases to the right. The PMMA PMMA us Abbe number. By tradition, the Abbe LaK8 BaK4 SK16 60 Glass BK7 Water Rare Earth 70 Fused Silica Glass Crown 80 FK51 number increases to the left, number so that dispersion locus of ordinary optical glasses based on silicon dioxide. The glass map plots index of refraction vers Glass Map OPTI-201/202 Geometrical and Instrumental Optics © CopyrightSCHOTT 2018 North John America, E. Greivenkamp Inc. 18-8 Glass Map –America, Inc. North Schott OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 18-9 liminate lead and arsenic. Lead is replaced liminate arsenic. Lead lead and changing the dispersion, barium oxide is the dispersion, barium oxide changing nd more difficult are also to polish. They oxide based (instead of silicon dioxide) and spersion and the index and moves the glass up and the index spersion and The new or environmentally safe glasses expensive just for the raw material expensive . nerally have better blue transmission. nerally have 50-60 separates the glasses into the two primary classifications: separates the glasses into two crown 50-60 ≈ the glass line. To increase the index without increase the index the glass line. To rare earth glasses are lanthanum The added. provide high index and low dispersion. from the glass line are softer a Glasses away be very can susceptible to staining. They index glasses are less Low dense and ge Glasses have been recently reformulated to e with other elements, especially titanium. on the manufacturer). usually carry an N, S or E prefix (depending The line at glass (low dispersion) and flint glass (low dispersion) and (high dispersion). The addition of lead oxide increases the di Glass Map - Continued OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 18-10 : 3 3
most common optical glass): most common 1. . d d The glass density is 2.51 g/cm glass density is 2.51 The n abcdef n abc de f 517642 1.517 64.2 The six-digit glass code specifies the index and the Abbe number: (the single BK7 For example The enhanced glass code also encodes the density of glass in g/cm also encodes glass code enhanced The For BK7: 517642.251 Glass Code OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 18-11 Rel $ P 0.33 0.25 0.26 0.33 ter, can vary from these from can vary ter, 55 30 31 60 designation. Equivalent glasses C n Ohara Corp. and Hoya 1.0003), and the indices should be corrected for 1.0003), ≈ F n n the plastic materials and wa the plastic materials ndices of the actual glass should be used in final be used in the actual glass should ndices of d n * Schott Glass Technologies Inc. Technologies * Schott Glass can also be obtained from e measured relative to air ( Material Code N-FK51*N-BK7LLF1 487845N-BaK4 1.48656N-KzFS4 517642 1.49056N-F2 1.51680 1.48480N-SK16 548458 569560 1.52238 613445N-SF2 84.5 1.54814 1.56883 1.51432 1.61336N-KzFS5 1.55655 1.57591 0.306 64.2 1.62300N-LaK8 1.54457 620364 620603 1.56575 35 1.60922N-LaF21 0.308 1.62005 1.62041 45.8 56.0 648338 654397N-SF6 44.5 1.63208 1.62756 1.0 0.298 0.303 1.64769 1.65412N-LaSF31A 713538 1.61506 1.61727 0.301 1.66125 1.66570 788475N-LaSF46A 2.5 5 1.71300 36.4 60.3 1.64210 23 1.64922 883408Fused Silica 1.78800 1.72222 0.294 0.305 805254 904313PMMA 1.88300 33.8 1.79960 39.7 1.70897 1.80518 458678 1.89822 1.90366 1.78301 3.5 3.5 0.292 0.297 53.8 1.82783 1.87656 1.92411 1.45847 47.5 3.5 0.304 1.79608 10 1.89526 1.46313 40.8 492574 0.301 25.4 1.45637 31.3 0.297 8 1.492 15 67.8 0.287 0.291 35 0.311 1.498 15 9 1.489 PolycarbonatePolystyrene 585299Water 1.585 590311 1.600 1.590 333560 1.580 1.604 1.333 1.585 1.337 1.331 Glass Data The properties of an individual sample, sample, especially an individual The properties of for catalog values. For precision systems, the measured i indices ar The listed designs. vacuum. use in OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 18-12 Approx. Glass Cost (2014): N-BK7 $11/lb N-LaK8 $85/lb N-FK51 $280/lb N-LaSF31 $380/lb fficients of thermal expansion, temperature thermal expansion, fficients of ngths, the glass catalog lists ngths, other materials ansmission as a function of wavelength, several ansmission as a function of wavelength, CR –CR (Scale 1-4) vapor resistance, water Climate –FR resistance (Scale 0-5) Stain SR – to acids (Scale 1-4 plus 51-53) Resistance –AR resistance (Scale 1-4) Alkali –PR resistance (Scale 1-4) Phosphate = Specific heat = Glass transition temperature = Internal transmission ( 5 mm and 25 mm thick) 25 mm and Internal transmission ( 5 = = Thermal conductivity = Density p g = Temperature coefficient of expansion i dn/dtTemperature coefficient of refractive index = Coefficients of the dispersion formula α T properties important for a design such as coe such design properties important for a internal tr refractive index, coefficients of chemical resistance values. properties, and mechanical Chemical properties (low is good): In addition to index data at various wavele HK = Knoop Hardness τ C Other Glass Properties OPTI-201/202 Geometrical and Instrumental Optics © CopyrightSCHOTT 2018 North John America, E. Greivenkamp Inc. 18-13 Glass Properties–America, Inc. Schott North OPTI-201/202 Geometrical and Instrumental Optics © CopyrightSCHOTT 2018 North John America, E. Greivenkamp Inc. 18-14 Glass Properties – North America, Inc. Schott OPTI-201/202 Geometrical and Instrumental Optics © CopyrightSCHOTT 2018 North John America, E. Greivenkamp Inc. 18-15 N-BK7– Schott North America, Inc. OPTI-201/202 Geometrical and Instrumental Optics © CopyrightSCHOTT 2018 North John America, E. Greivenkamp Inc. 18-16 N-BK7– Schott North America, Inc. OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 18-17 /°C /°C -6 -7 = 5.5x10 = 7.1x10 /°C -7 . May not be a good choice for thick choice . May not be a good = 0 +/- 1x10 Fused Silica CER-VIT ULE Zerodur ; not crystalline ; not (amorphous) 2 Good UV transmission to about 200 nm (depends on purity) for microlithography lenses Used Low thermal expansion: BK7 Pure SiO windows. Partially crystallized glasses – glass ceramics Note: Fused silica of index with temperature even has an extremely high change though it is dimensionally very stable Fused Silica or Fused Quartz: Low Expansion Materials: Other Optical Materials OPTI-201/202 Geometrical and Instrumental Optics © Copyright 2018 John E. Greivenkamp 18-18 m m and 25-300 m m m m m m (Fluorite) m m (36% for Ge) –coating. AR require rials may be single-point diamond turned. 1.7 .25-55 1.6 .22-55 1.35 .12-5 1.5 .2-20 2.4 .6-16 1.4 .13-7 3.4 4 1.2-7.0 2.2 2-14 3-12 ≈ ≈ ≈ ≈ ≈ ≈ ≈ ≈ ≈ n 2 Polystyrene Polycarbonate CsI n CsBr n LiF n CaF NaCl n Ge n ZnS n ZnSe n Index changes with water absorption. Most common: Acrylic (PMMA) (Plexiglas) A high index implies high Fresnel reflections Some of the materials are sensitive to water vapor. Some provide excellent transmission and the IR. in the UV Some are very soft and fragile – hard to polish. For IR applications, some of the mate Some are birefringent. Others are polycrystalline –to scattering. prone to obtain transmission way in the IR. Often the only Examples: n Si More Optical Materials Plastics:also be cast. Usually molded; can Crystalline Materials: