Gaussian Beam OpticsLaser GuideMachine Vision GuideFundamental OpticsOptical SpecicationsMaterial PropertiesOptical Coatings & MaterialsA57 marketplace.idexop.comINTRODUCTIONA58OPTICAL PROPERTIESA59MECHANICAL AND CHEMICAL PROPERTIESA61LENS MATERIALSA63MAGNESIUM FLUORIDEA64CALCIUM FLUORIDEA65SUPRASIL 1A66UV-GRADE SYNTHETIC FUSED SILICAA67CRYSTAL QUARTZA69CALCITEA70SCHOTT GLASSA71OPTICAL CROWN GLASSA73LOW-EXPANSION BOROSILICATE GLASSA74ZERODURA75INFRASIL 302A76SAPPHIREA77ZINC SELENIDEA78SILICONA79GERMANIUMA80MATERIAL PROPERTIES OVERVIEWA81MATERIAL PROPERTIESMaterial PropertiesMATERIAL PROPERTIESA58 1-505-298-2550 IntroductionTHERMAL CHARACTERISTICSThe thermal expansion coeffcient can be particularly important in applications in which the part is subjected to high temperatures, such as high-intensity projection systems. This is also of concern when components must undergo large temperature cycles, such as in optical systems used outdoors.MECHANICAL CHARACTERISTICSThe mechanical characteristics of a material are signifcant in many areas. They can affect how easy it is to fabricate the material into shape, which affects product cost. Scratch resistance is important if the component will require frequent cleaning. Shock and vibration resistance are important for military, aerospace, or certain industrial applications. Ability to withstand high pressure differentials is important for windows used in vacuum chambers.CHEMICAL CHARACTERISTICSThe chemical characteristics of a material, such as acid or stain resistance, can also affect fabrication and durability. As with mechanical characteristics, chemical characteristics should be taken into account for optics used outdoors or in harsh conditions.COSTCost is almost always a factor to consider when specifying materials. Furthermore, the cost of some materials, such as UV-grade synthetic fused silica, increases sharply with larger diameters because of the diffculty in obtaining large pieces of the material.Glass manufacturers provide hundreds of different glass types with differing optical transmission and mechanical strengths. CVI Laser Optics has simplifed the task of selecting the right material for an optical component by offering each of our standard componentsin a single material, or in a small range of materials best suited to typical applications.There are, however, two instances in which one might need to know more about optical materials: one might need to determine the performance of a catalog component in a particular application, or one might need specifc information to select a material for a custom component. The information given in this chapter is intended to assist in that process.The most important material properties to consider in regard to an optical element are as follows:X Transmission versus wavelengthX Index of refractionX Thermal characteristicsX Mechanical characteristicsX Chemical characteristicsX Cost TRANSMISSION VERSUS WAVELENGTHA material must transmit effciently at the wavelengthof interest if it is to be used for a transmissive component. A transmission curve allows the optical designer to estimate the attenuation of light as a function of wavelength caused by internal material properties. For mirror substrates, the attenuation may be of no consequence.INDEX OF REFRACTIONThe index of refraction, as well as the rate of change ofindex with wavelength (dispersion), might require consideration. High-index materials allow the designer to achieve a given power with less surface curvature, typically resulting in lower aberrations. On the other hand, most high-index fint glasses have higher dispersion, resulting in more chromatic aberration in polychromatic applications. They also typically have poorer chemical characteristics than lower-index crown glasses.INTRODUCTIONMATERIAL PROPERTIESGaussian Beam OpticsLaser GuideMachine Vision GuideFundamental OpticsOptical SpecicationsMaterial PropertiesOptical Coatings & MaterialsA59 marketplace.idexop.com Optical Propertiesmaterial dispersion formula found in the next section. These results are applicable to monochromatic. Both and n are functions of wavelength.To calculate either Ti or the Te for a lens at any wavelength of interest, frst fnd the value of absorption coeffcient . Typically, internal transmittance Ti is tabulated as a function of wavelength for two distinct thicknesses tc1 and tc2, and m must be found from these. Thus where the bar denotes averaging. In portions of the spectrum where absorption is strong, a value for Ti is typically given only for the lesser thickness. Thenm = 1tTci. ln(2.5)When it is necessary to fnd transmittance at wavelengths other than those for which Ti is tabulated, use linear interpolation.The on-axis Te value is normally the most useful, but some applications require that transmittance be known along other ray paths, or that it be averaged over the entire lens surface. The method outlined above is easily extended to encompass such cases. Values of t1 and t2 must be found from complete Fresnel formulas for arbitrary angles of incidence. The angles of incidence will be different at the two surfaces; therefore, t1 and t2 will generally be unequal. Distance tc, which becomes the surface-to-surface distance along a particular ray, must be determined by ray tracing. It is necessary to account separately for the s- and p-planes of polarization, and it is usually suffcient to average results for both planes at the end of the calculation.REFRACTIVE INDEX AND DISPERSIONThe Schott Optical Glass catalog offers nearly 300 different optical glasses. For lens designers, the most important difference among these glasses is the index of refraction and dispersion (rate of change of index with wavelength). Typically, an optical glass is specifed by its index of refraction at a wavelength in the middle of the visible spectrum, usually 587.56 nm (the helium d-line), and by the Abb v-value, defned to beThe most important optical properties of a material are its internal and external transmittances, surface refectance, and refractive indexe. The formulas that connect these variables in the on-axis case are presented below.TRANSMISSIONExternal transmittance is the single-pass irradiance transmittance of an optical element. Internal transmittance is the single-pass irradiance transmittance in the absence of any surface refection losses (i.e., transmittance of the material itself). External transmittance is of paramount importance when selecting optics for an image-forming lens system because external transmittance neglects multiple refections between lens surfaces. Transmittance measured with an integrating sphere will be slightly higher. If Te denotes the desired external irradiance transmittance, Ti the corresponding internal transmittance, t1 the single-pass transmittance of the frst surface, and t2 the single-pass transmittance of the second surface, then T t t T t t ee itc= =1 2 1 2m(2.1)where e is the base of the natural system of logarithms, is the absorption coeffcient of the lens material, and tc is the lens center thickness. This allows for the possibility that the lens surfaces might have unequal transmittances (for example, one is coated and the other is not). Assuming that both surfaces are uncoated,t t r rrnn1 2221211= +=+where(2.2)wheret t r rrnn1 2221211= +=+where(2.3)is the single-surface single-pass irradiance refectance at normal incidence as given by the Fresnel formula. The refractive index n must be known or calculated from the OPTICAL PROPERTIESMaterial PropertiesMATERIAL PROPERTIESA60 1-505-298-2550glass is annealed (heated and cooled) to remove any residual stress left over from the original manufacturing process. Schott Glass defnes fne annealed glass to have a stress birefringence of less than or equal to 10 nm/cm for diameters less than 300 mm and for thicknesses less than or equal to 60 mm. For diameters between 300 and 600 mm and for thicknesses between 60 and 80 mm, stress birefringence would be less than or equal to 12 nm/cm.Optical Properties vd = (nd1)/ (nF-nC). The designations F and C stand for 486.1 nm and 656.3 nm, respectively. Here, vd shows how the index of refraction varies with wavelength. The smaller vd is, the faster the rate of change is. Glasses are roughly divided into two categories: crowns and fints. Crown glasses are those with nd < 1.60 and vd > 55, or nd > 1.60 and vd > 50. The others are fint glasses.The refractive index of glass from 365 to 2300 nm can be calculated by using the formulanBCBCBC2 1 221222232231 =++llllll(2.6)Here , the wavelength, must be in micrometers, and the constants B1 through C3 are given by the glass manufacturer. Values for other glasses can be obtained from the manufacturers literature. This equation yields an index value that is accurate to better than 1x105 over the entire transmission range, and even better in the visible spectrum.OTHER OPTICAL CHARACTERISTICSREFRACTIVE INDEX HOMOGENEITYThe tolerance for the refractive index within melt for all Schott fne annealed glass used in CVI Laser Optics catalog components is 1x104.Furthermore, the refractive index homogeneity, a measure of deviation within a single piece of glass, is better than 2x105.STRIAE GRADEStriae are thread-like structures representing subtle but visible differences in refractive index within an optical glass. Striae classes are specifed in ISO 10110. All CVI Laser Optics catalog components that utilize Schott optical glass are specifed to have striae that conform to ISO 10110 class 5 indicating that no visible striae, streaks, or cords are present in the glass.STRESS BIREFRINGENCEMechanical stress in optical glass leads to birefringence (anisotropy in index of refraction) which can impair the optical performance of a fnished component. Optical Synthetic fused silica is an ideal optical material for many laser applications. It is transparent from as low as 180 nm to over 2.0 m, has low coefficient of thermal expansion, and is resistant to scratching and thermal shock.APPLICATION NOTEFused-Silica OpticsMATERIAL PROPERTIESGaussian Beam OpticsLaser GuideMachine Vision GuideFundamental OpticsOptical SpecicationsMaterial PropertiesOptical Coatings & MaterialsA61 marketplace.idexop.com0.3 acid solution, and values from 51 to 53 are used for glass with too little resistance to be tested with such a strong solution.ALKALI AND PHOSPHATE RESISTANCE Alkali resistance is also important to the lens manufacturer since the polishing process usually takes place in an alkaline solution. Phosphate resistance is becoming more signifcant as users move away from cleaning methods that involve chlorofuorocarbons (CFCs) to those that may be based on traditional phosphate-containing detergents. In each case, a two-digit number is used to designate alkali or phosphate resistance. The frst number, from 1 to 4, indicates the length of time that elapses before any surface change occurs in the glass, and the second digit reveals the extent of the change.MICROHARDNESSThe most important mechanical property of glass is microhardness. A precisely specifed diamond scribe is placed on the glass surface under a known force. The indentation is then measured. The Knoop and the Vickers microhardness tests are used to measure the hardness of a polished surface and a freshly fractured surface, respectively.Mechanical and chemical properties of glass are important to lens manufacturers. These properties can also be signifcant to the user, especially when the component will be used in a harsh environment. Different polishing techniques and special handling may be needed depending on whether the glass is hard or soft, or whether it is extremely sensitive to acid or alkali.To quantify the chemical properties of glasses, glass manufacturers rate each glass according to four categories: climatic resistance, stain resistance, acid resistance, and alkali and phosphate resistance.CLIMATIC RESISTANCEHumidity can cause a cloudy flm to appear on the surface of some optical glass. Climatic resistance expresses the susceptibility of a glass to high humidity and high temperatures. In this test, glass is placed in a water vapor-saturated environment and subjected to a temperature cycle which alternately causes condensation and evaporation. The glass is given a rating from 1 to 4 depending on the amount of surface scattering induced by the test. A rating of 1 indicates little or no change after 30 hours of climatic change; a rating of 4 means a signifcant change occurred in less than 30 hours.STAIN RESISTANCEStain resistance expresses resistance to mildly acidic water solutions, such as fngerprints or perspiration. In this test, a few drops of a mild acid are placed on the glass. A colored stain, caused by interference, will appear if the glass starts to decompose. A rating from 0 to 5 is given to each glass, depending on how much time elapses before stains occur. A rating of 0 indicates no observed stain in 100 hours of exposure; a rating of 5 means that staining occurred in less than 0.2 hours.ACID RESISTANCEAcid resistance quantifes the resistance of a glass tostronger acidic solutions. Acid resistance can be particularly important to lens manufacturers because acidic solutions are typically used to strip coatings from glass or to separate cemented elements. A ratingfrom 1 to 4 indicates progressively less resistance to a pH Mechanical and Chemical PropertiesMECHANICAL AND CHEMICAL PROPERTIESMaterial PropertiesMATERIAL PROPERTIESA62 1-505-298-2550 Mechanical and Chemical PropertiesThe catalogs of optical glass manufacturers contain products covering a very wide range of optical characteristics. However, it should be kept in mind that the glass types that exhibit the most desirable properties in terms of index of refraction and dispersion often have the least practical chemical and mechanical characteristics. Furthermore, poor chemical and mechanical attributes translate directly into increased component costs because working these sensitive materials increases fabrication time and lowers yield. Please contact us before specifying an exotic glass in an optical design so that we can advise you of the impact that that choice will have on part fabrication.APPLICATION NOTEGlass ManufacturersKnoop Hardness Values for StandardOptical MaterialsMaterialKnoop HardnessMagnesium Fluoride415Calcium Fluoride158Fused Silica522BK7 (N-BK7)610Optical Crown Glass542Borosilicate Glass480Zerodur620Zinc Selenide112Silicon1100Germanium780MATERIAL PROPERTIESGaussian Beam OpticsLaser GuideMachine Vision GuideFundamental OpticsOptical SpecicationsMaterial PropertiesOptical Coatings & MaterialsA63 marketplace.idexop.cominto the ultraviolet range.N-BK7 refers to the lead and arsenic-free version of BK7, with most optical properties identical between the two.CVI Laser Optics reserves the right, without prior notice, to make material changes or substitution on any optical component.CVI Laser Optics lenses are made of synthetic fused silica, N-BK7 grade A fne annealed glass, and several other materials. The following table identifes the materials used in CVI Laser Optics lenses. Some of these materials are also used in prisms, mirror substrates, and other products.Glass type designations and physical constants are the same as those published by Schott Glass. CVI Laser Optics occasionally uses corresponding glasses made by other glass manufacturers but only when this does not result in a signifcant change in optical properties.The performance of optical lenses and prisms depends on the quality of the material used. No amount of skill during manufacture can eradicate striae, bubbles, inclusions, or variations in index. CVI Laser Optics takes considerable care in its material selection, using only frst-class optical materials from reputable glass manufacturers. The result is reliable, repeatable, consistent performance.The following physical constant values are reasonable averages based on historical experience. Individual material specimens may deviate from these means. Materials having tolerances more restrictive than those published in the rest of this chapter, or materials traceable to specifc manufacturers, are available only on special request.N-BK7 OPTICAL GLASSA borosilicate crown glass, N-BK7, is the material used in many CVI Laser Optics products. N-BK7 performs well in chemical tests so that special treatment during polishing is not necessary. N-BK7, a relatively hard glass, does not scratch easily and can be handled without special precautions. The bubble and inclusion content of N-BK7 is very low, with a cross-section total less than 0.029 mm2 per 100 cm3. Another important characteristic of N-BK7 is its excellent transmittance, at wavelengths as low as 350 nm. Because of these properties, N-BK7 is used widely throughout the optics industry. A variant of N-BK7, designated UBK7, has transmission at wavelengths as low as 300 nm. This special glass is useful in applications requiring a high index of refraction, the desirable chemical properties of N-BK7, and transmission deeper Lens MaterialsLENS MATERIALSLens Material TableMaterial Product CodeSynthetic Fused Silica UV GradeLUP-UVLUK-UVPLCX-UVPLCC-UVLUD-UVLUB-UVBICX-UVBICC-UVRCX-UVRCC-UVSCX-UVSCC-UVCLCX-UVCLCC-UVBFPL-UVSynthetic Fused Silica Excimer Grade PLCX-EUVN-BK7 Grade A Fine AnnealedLPX-C LPK-CPLCX-CPLCC-CLDX-CLDK-CBICX-CBICC-CLCP-CLCN-CRCX-CRCC-CSCX-CSCC-CCLCC-CCLCX-CMENP-CMENN-CBFPL-CLaSFN9 Grade A Fine AnnealedLMS and selected LPX seriesSK11 and SF5 Grade A Fine Annealed LAIBaK1 Grade A Fine Annealedselected LPX seriesSF11 Grade-A Fine AnnealedPLCX-SF11PLCC-SF11LAPLANOptical Crown GlassLAGLow-Expansion Borosilicate Glass (LEBG) selected CMP seriesSapphirePXSCalcium FluoridePLCX-CFUVPLCX-CFIRRCX-CFUVRCC-CFUVMagnesium FluorideBICX-MF PLCX-MFZinc SelenidePLCX-ZnSeMENP-ZnSeVarious Glass Combinations (including lead- and arsenic-free glasses)LAOLALAAPFAPHAPHANYAPYANLBMLSLGLCOASMaterial PropertiesMATERIAL PROPERTIESA64 1-505-298-2550 Magnesium FluorideMagnesium Fluoride (MgF2) is a tetragonal positive birefringent crystal grown using the vacuum Stockbarger technique. MgF2 is a rugged material resistant to chemical etching as well as mechanical and thermal shock. High-vacuum UV transmission and resistance to laser damage make MgF2 a popular choice for VUV and excimer laser windows, polarizers, and lenses.MAGNESIUM FLUORIDESpecificationsDensity: 3.177 g/cm3Youngs Modulus: 138.5 GPaPoissons Ratio: 0.271Knoop Hardness: 415Coeffcient of Thermal Expansion:8.48x106/C (perpendicular to c axis)13.70x106/C (parallel to c axis)Melting Point: 1585CDispersion Constants (Ordinary Ray): B1=4.87551080x101 B2=3.98750310x101 B3=2.31203530 C1=1.88217800x103 C2=8.95188847x103 C3=5.66135591x102Dispersion Constants (Extraordinary Ray):B1=4.13440230x101 B2=5.04974990x101 B3=2.49048620 C1=1.35737865x103 C2=8.23767167x103 C3=5.65107755x102Refractive Index of Magnesium FluorideWavelength (nm) Index of Refraction Ordinary Ray (nO) Index of Refraction Extraordinary Ray (nE)1931.427671.441272131.416061.429332221.412081.425222261.410491.423582441.404471.417352481.403341.416182571.401021.413772661.398961.411642801.396201.408773081.391881.404293251.389831.402163371.388591.400863511.387301.399523551.386961.39917MATERIAL PROPERTIESGaussian Beam OpticsLaser GuideMachine Vision GuideFundamental OpticsOptical SpecicationsMaterial PropertiesOptical Coatings & MaterialsA65 marketplace.idexop.com Calcium FluorideCalcium fuoride (CaF2), a cubic single-crystal material, has widespread applications in the ultraviolet and infrared spectrum. CaF2 is an ideal material for use with excimer lasers. It can be manufactured into windows, lenses, prisms, and mirror substrates.CaF2 transmits over the spectral range of about 130 nm to 10 mm. Traditionally, it has been used primarily in the infrared, rather than in the ultraviolet. CaF2 occurs naturally and can be mined. It is also produced synthetically using the time- and energy-consuming Stockbarger method. Unfortunately, achieving acceptable deep ultraviolet transmission and damage resistance in CaF2 requires much greater material purity than in the infrared, and it completely eliminates the possibility of using mined material.To meet the need for improved component lifetime and transmission at 193 nm and below, manufacturers have introduced a variety of inspection and processing methods to identify and remove various impurities at all stages of the production process. The needs for improved material homogeneity and stress birefringence have also caused producers to make alterations to the traditional Stockbarger approach. These changes allow tighter temperature control during crystal growth,as well as better regulation of vacuum and annealing process parameters.Excimer-grade CaF2 provides the combination of deep ultraviolet transmission (down to 157 nm), high damage threshold, resistance to color-center formation, low fuorescence, high homogeneity, and low stress-birefringence characteristics required for the most demanding deep ultraviolet applications.External transmittance for 5 mm thickuncoated calcium uorideCALCIUM FLUORIDEWavelength in Micrometers100Percent ExternalTransmittance80401.060203.5 3.0 2.0ordinary rayextraordinary raySpecificationsDensity: 3.18 g/cm3 @ 25CYoungs Modulus: 1.75x107 psiPoissons Ratio: 0.26Knoop Hardness: 158Thermal Coeffcient of Refraction: dn/dT =10.6x106/CCoeffcient of Thermal Expansion: 18.9x106/C (2060C)Melting Point: 1360CDispersion Constants:B1 = 0.5675888 B2 = 0.4710914 B3 = 3.8484723 C1 = 0.00252643 C2 = 0.01007833 C3 = 1200.5560Refractive Index of Calcium FluorideWavelength (m)Index of Refraction0.1931.5010.2481.4680.2571.4650.2661.4620.3081.4530.3551.4460.4861.4370.5871.4330.651.4320.71.4311.01.4281.51.4262.01.4232.51.4213.01.4174.01.4095.01.3986.01.3857.01.3698.01.349Material PropertiesMATERIAL PROPERTIESA66 1-505-298-2550Suprasil 1 is a type of fused silica with high chemical purity and excellent multiple axis homogeneity.With a metallic content less than 8 ppm, Suprasil 1 has superior UV transmission and minimal fuorescence.Suprasil 1 is primarily used for low fuorescence UV windows, lenses and prisms where multiple axis homogeneity is required.Suprasil 1SUPRASIL 1Wavelength in Micrometers0.2100Percent ExternalTransmittance80401.0 4.0602010.0 0.6 0.4 0.8 2.0External transmittance for 5 mm thickuncoated calcium uorideSpecificationsAbb Constant: 67.80.5Change of Refractive Index with Temperature (0 to 700C): 1.28x105/CHomogeneity (maximum index variation over 10-cm aperture): 2x105Knoop Hardness: 590Density: 2.20 g/cm3 @ 25CContinuous Operating Temperature: 900C maximumCoeffcient of Thermal Expansion: 5.5x107/CSpecifc Heat: 0.177 cal/g/C @ 25CDispersion Constants:B1 = 0.6961663 B2 = 0.4079426 B3 = 0.8974794 C1 = 0.0046791 C2 = 0.0135121 C3 = 97.9340025Refractive Index of Suprasil 1*Wavelength (nm)Index of Refraction193.41.56013248.41.50833266.01.49968308.01.48564325.01.48164337.01.47921365.51.47447404.71.46962435.81.46669441.61.46622447.11.46578486.11.46313488.01.46301514.51.46156532.01.46071546.11.46008587.61.45846632.81.45702656.31.45637694.31.45542752.51.45419905.01.451681064.01.449631153.01.448591319.01.44670* Accuracy 3 x 10-5MATERIAL PROPERTIESGaussian Beam OpticsLaser GuideMachine Vision GuideFundamental OpticsOptical SpecicationsMaterial PropertiesOptical Coatings & MaterialsA67 marketplace.idexop.com UV-Grade Synthetic Fused SilicaSynthetic fused silica (amorphous silicon dioxide), by chemical combination of silicon and oxygen, is an ideal optical material for many applications. It is transparent over a wide spectral range, has a low coeffcient of thermal expansion, and is resistant to scratching and thermal shock.The synthetic fused silica materials used by CVI Laser Optics are manufactured by fame hydrolysis to extremely high standards. The resultant material is colorless and non-crystalline, and it has an impurity content of only about one part per million.Synthetic fused silica lenses offer a number of advantages over glass or fused quartz:X Greater ultraviolet and infrared transmissionX Low coeffcient of thermal expansion, which provides stability and resistance to thermal shock over large temperature excursionsX Wider thermal operating rangeX Increased hardness and resistance to scratchingX Much higher resistance to radiation darkening from ultraviolet, x-rays, gamma rays, and neutrons.UV-grade synthetic fused silica (UVGSFS or Suprasil 1) is selected to provide the highest transmission (especially in the deep ultraviolet) and very low fuorescence levels (approximately 0.1% that of fused natural quartz excited at 254 nm). UV-grade synthetic fused silica does not fuoresce in response to wavelengths longer than 290 nm. In deep ultraviolet applications, UV-grade synthetic fused silica is an ideal choice. Its tight index tolerance ensures highly predictable lens specifcations.The batch-to-batch internal transmittance of synthetic fused silica may fuctuate signifcantly in the near infrared between 900 nm and 2.5 m due to resonance absorption by OH chemical bonds. Ifthe optic is to be used in this region, Infrasil 302 may be a better choice.UV-GRADE SYNTHETIC FUSED SILICASpecificationsAbb Constant: 67.80.5Change of Refractive Index with Temperature (0 to 700C): 1.28x10-5/CHomogeneity (maximum index variation over 10-cm aperture): 2x105Density: 2.20 g/cm3 @ 25CKnoop Hardness: 522Continuous Operating Temperature: 900C maximumCoeffcient of Thermal Expansion: 5.5x10-7/CSpecifc Heat: 0.177 cal/g/C @ 25CDispersion Constants:B1 = 0.6961663 B2 = 0.4079426 B3 = 0.8974794 C1 = 0.0046791 C2 = 0.0135121 C3 = 97.9340025Refractive Index of UV-Grade Synthetic Fused Silica*Wavelength (nm)Index of Refraction180.01.58529190.01.56572200.01.55051213.91.53431226.71.52275230.21.52008239.91.51337248.31.50840265.21.50003275.31.49591280.31.49404289.41.49099296.71.48873302.21.48719330.31.48054340.41.47858351.11.47671361.11.47513365.01.47454404.71.46962435.81.46669* Accuracy 3 x 10-5Material PropertiesMATERIAL PROPERTIESA68 1-505-298-2550 UV-Grade Synthetic Fused SilicaWavelength in Nanometers140100Percent ExternalTransmittance8050040220 2606020300 340 380 180 420 460Wavelength in MicrometersPercent ExternalTransmittance5.0 1.5 2.0 2.5 3.0 3.5 1.0 4.0 4.5a) Lower Limitsb) Upper Limits0.510080406020N-BK7UVGSFSUVGSFSN-BK7Refractive Index of UV-Grade Synthetic Fused Silica*Wavelength (nm)Index of Refraction441.61.46622457.91.46498476.51.46372486.11.46313488.01.46301496.51.46252514.51.46156532.01.46071546.11.46008587.61.45846589.31.45840632.81.45702643.81.45670656.31.45637694.31.45542706.51.45515786.01.45356820.01.45298Refractive Index of UV-Grade Synthetic Fused Silica*Wavelength (nm)Index of Refraction830.01.45282852.11.45247904.01.451701014.01.450241064.01.449631100.01.449201200.01.448051300.01.446921400.01.445781500.01.444621550.01.444021660.01.442671700.01.442171800.01.440871900.01.439512000.01.438092100.01.43659Comparison of uncoated external transmittances for UVGSFS and N-BK7, all 10 mm in thickness* Accuracy 3 x 10-5MATERIAL PROPERTIESGaussian Beam OpticsLaser GuideMachine Vision GuideFundamental OpticsOptical SpecicationsMaterial PropertiesOptical Coatings & MaterialsA69 marketplace.idexop.com Crystal QuartzCrystal quartz is a positive uniaxial birefringent single crystal grown using a hydrothermal process. Crystal quartz from CVI Laser Optics is selected to minimize inclusions and refractive index variation. Crystal quartz is most commonly used for high-damage-threshold waveplates and solarization-resistant Brewster windows for argon lasers.The dispersion for the index of refraction is given by the Laurent series shown below.h2 = A0 = A1l2 = = = =A5l8A2l2A4l6A3l4CRYSTAL QUARTZSpecificationsTransmission Range: 0.1702.8 mMelting Point: 1463CKnoop Hardness: 741Density: 2.64 g/cm3Youngs Modulus, Perpendicular: 76.5 GPaYoungs Modulus, Parallel: 97.2 GPaThermal Expansion Coeffcient, Perpendicular: 13.2x106/CThermal Expansion Coeffcient, Parallel: 7.1x106/CDispersion Constants (Ordinary Ray): A0=2.35728 A1=41.17000x102 A2=1.05400x102 A3=1.34143x104 A4=44.45368x107 A5=5.92362x108Dispersion Constants (Extraordinary Ray): A0=2.38490 A1=41.25900x102 A2=1.07900x102 A3=1.65180x104 A4=41.94741x107 A5=9.36476x108Refractive Index of Crystal QuartzWavelength (nm) Index of Refraction Ordinary Ray (nO) Index of Refraction Extraordinary Ray (nE)1931.660911.674552131.632241.644522221.622381.634272261.618591.630332441.604391.615622481.601751.612892571.596201.607142661.591641.602422801.585331.595893081.575561.585773251.570971.581023371.568171.578123511.565331.575183551.564631.574464001.557721.567304421.553241.562664581.551811.561194881.549551.558855151.547871.557115321.546901.556105901.544211.553336331.542641.551716701.541481.550516941.540801.549817551.539321.548277801.538781.547718001.538371.547298201.537981.546888601.537241.546129801.535311.54409Wavelength in Micrometers0.15100Percent ExternalTransmittance80400.5 2.560203.5 0.25 0.20 0.30 1.5External transmittance for 10 mm thick uncoated crystal quartzMaterial PropertiesMATERIAL PROPERTIESA70 1-505-298-2550Calcite (CaCO3) is a naturally occurring negative uniaxial crystal which exhibits pronounced birefringence. Strong birefringence and a wide transmission range have made this mineral popular for making polarizing prisms for over 100 years. Although it can now be grown artifcially in small quantities, most optical calcite is mined in Mexico, Africa, and Siberia. Finding optical grade crystals remains a time-consuming task requiring special skills. Cutting and polishing calcite is also challenging due to the softness of the mineral and its tendency to cleave easily. These factors explain why, even many years after the techniques were developed, calcite prisms remain expensive when compared to other types of polarizers.Since calcite is a natural crystal, the transmission will vary from piece to piece. In general, a 10 mm thick sample will fall within the following ranges: 350 nm, 40 45%; 400 nm, 70 75%; 500 2300 nm, 86 88%.CalciteCALCITESpecificationsDensity: 2.71 g/cm3Mohs Hardness: 3Melting Point: 1339 CDispersion Constants (Ordinary Ray): B1 = 1.56630 B2 = 1.41096 B3 = 0.28624 C1 = 105.58893 C2 = 0.01583669 C3 =40.01182893Dispersion Constants (Extraordinary Ray): B1 = 8.418192x105 B2 = 1.183488 B3 = 0.03413054 C1 = 0.3468576 C2 = 7.741535x103 C3 = 12.185616Wavelength in Micrometers100Percent ExternalTransmittance80401.060203.5 3.0 2.0ordinary rayextraordinary rayTypical external transmittance for 10 mm thick calciteRefractive Index of CalciteWavelength (nm) Index of Refraction Ordinary Ray (nO) Index of Refraction Extraordinary Ray (nE)2501.769061.533363501.696951.503924501.672761.493075501.661321.487756501.654671.484737501.650411.482898501.647241.481579501.644701.4805610501.642601.4798011501.640681.4791612501.638891.4779213501.637151.4780314501.635411.4776515501.633651.4772216501.631861.4768117501.629951.4763818501.627981.4759719501.625941.4755520501.623791.4751321501.621491.4748622501.619211.4748223501.616981.47528MATERIAL PROPERTIESGaussian Beam OpticsLaser GuideMachine Vision GuideFundamental OpticsOptical SpecicationsMaterial PropertiesOptical Coatings & MaterialsA71 marketplace.idexop.comThe following tables list the most important optical and physical constants for Schott optical glass types BK7, SF11, LaSFN9, BaK1, and F2, with N-BK7 and N-BaK1 denoting the lead and arsenic-free versions of BK7 and BaK1. These types are used in most CVI Laser Optics simple lens products and prisms. Index of refraction as well as the most commonly required chemical characteristics and mechanical constants, are listed. Further numerical data and a more detailed discussion of the various testing processes can be found in the Schott Optical Glass catalog.Schott GlassSCHOTT GLASSPhysical Constants of Schott GlassesGlass TypeBK7 (N-BK7)SF11LaSFN9BaK1 (N-BaK1)F2Melt-to-Melt Mean Index Tolerance0.00050.00050.00050.00050.0005Stress Birefringence nm/cmYellow Light1010101010Abb Factor (vd)64.1725.7632.1757.5536.37Constants of Dispersion Formula:B1 1.039612121.738484031.978881941.123656621.34533359B2 2.31792344x101 3.11168974x101 3.20435298x101 3.09276848x101 2.09073176x101B3 1.010469451.174908711.929007518.81511957x101 9.37357162x101C1 6.00069867x103 1.36068604x10-4 1.18537266x102 6.44742752x103 9.97743871x103C2 2.00179144x102 6.15960463x10-2 5.27381770x102 2.22284402x102 4.70450767x102C3 1.03560653x1021.21922711x1021.66256540x1021.07297751x1021.11886764x102Density (g/cm3)2.514.744.443.193.61Coefcient of Linear Thermal Expansion (cm/C):30 to +70C7.1x1046 6.1x1046 7.4x1046 7.6x1046 8.2x1046+20 to +300C8.3x1046 6.8x1046 8.4x1046 8.6x1046 9.2x1046Transition Temperature557C505C703C592C438CYoungs Modulus (dynes/mm2)8.20x109 6.60x109 1.09x1010 7.30x1095.70x109Climate Resistance21221Stain Resistance00010Acid Resistance1.01.02.03.31.0Alkali Resistance2.01.21.01.22.3Phosphate Resistance2.31.01.02.01.3Knoop Hardness610450630530420Poissons Ratio0.2060.2350.2860.2520.220Material PropertiesMATERIAL PROPERTIESA72 1-505-298-2550 Schott GlassRefractive Index of Schott GlassWavelength (nm)Refractive Index, n Fraunhofer Designation Source Spectral Region BK7 (N-BK7)SF11LaSFN9BaK1 (N-BaK1)F2351.11.538941.600621.67359Ar laserUV363.81.536491.597441.66682Ar laserUV404.71.530241.842081.898441.589411.65064hHg arcViolet435.81.526681.825181.884671.584881.64202gHg arcBlue441.61.526111.822591.882531.584151.64067HeCd laserBlue457.91.524611.815961.877001.582261.63718Ar laserBlue465.81.523951.813071.874581.581411.63564Ar laserBlue472.71.523391.810701.872591.580711.63437Ar laserBlue476.51.523091.809461.871531.580341.63370Ar laserBlue480.01.522831.808341.870591.580001.63310FCd arcBlue486.11.522381.806451.868991.579431.63208FH2 arcBlue488.01.522241.805901.868521.579271.63178Ar laserBlue496.51.521651.803471.866451.578521.63046Ar laserGreen501.71.521301.802051.865241.578091.62969Ar laserGreen514.51.520491.798801.862451.577071.62790Ar laserGreen532.01.519471.794791.859011.575801.62569Nd laserGreen546.11.518721.791901.856511.574871.62408eHg arcGreen587.61.516801.784721.850251.572501.62004dHe arcYellow589.31.516731.784461.850021.572411.61989DNa arcYellow632.81.515091.778621.844891.570411.61656HeNe laserRed643.81.514721.777341.843761.569971.61582CCd arcRed656.31.514321.775991.842561.569491.61503CH2 arcRed694.31.513221.772311.839281.568161.61288Ruby laser Red786.01.511061.765581.833231.565641.60889IR821.01.510371.763591.831421.564851.60768IR830.01.510201.763111.830981.564661.60739GaAlAslaser IR852.11.509801.762001.829971.564211.60671sCe arcIR904.01.508931.759701.827851.563251.60528GaAs laserIR1014.01.507311.755791.82420 1.561521.60279 tHg arcIR1060.01.506691.754451.822931.560881.60190Nd laserIR1300.01.503701.749011.817641.557961.59813 InGaAsP laser IR1500.01.501271.745541.814121.555751.59550IR1550.01.500651.744741.813291.555201.59487IR1970.11.494951.738431.806571.550321.58958Hg arcIR2325.41.489211.732941.800551.545561.58465Hg arcIRMATERIAL PROPERTIESGaussian Beam OpticsLaser GuideMachine Vision GuideFundamental OpticsOptical SpecicationsMaterial PropertiesOptical Coatings & MaterialsA73 marketplace.idexop.comIn optical crown glass, a low-index commercial-grade glass, the index of refraction, transmittance, and homogeneity are not controlled as carefully as they are in optical-grade glasses such as N-BK7. Optical crown glass is suitable for applications in which component tolerances are fairly loose, and as a substrate material for mirrors.Optical Crown GlassOPTICAL CROWN GLASSSpecificationsGlass Type Designation: B270Abb Constant: 58.5Dispersion: (nFnC) = 0.0089Knoop Hardness: 542Density: 2.55 g/cm3 @ 23CYoungs Modulus: 71.5 kN/mm2Specifc Heat: 0.184 cal/g/C (20C to 100C)Coeffcient of Thermal Expansion: 93.3x107/C (20C to 300C)Transformation Temperature: 521CSoftening Point: 708CWavelength in Micrometers100Percent ExternalTransmittance804030060203000 2000 400 500 1000External transmittance for 10 mm thick uncoated optical crown glassRefractive Index of Optical Crown GlassWavelength (nm) Index of Refraction Fraunhofer Designation Source Spectral Region435.81.53394gHg arcBlue480.01.52960FCd arcBlue486.11.52908FH2 arcBlue546.11.52501eHg arcGreen587.61.52288dHe arcYellow589.01.52280DNa arcYellow643.81.52059CCd arcRed656.31.52015CH2 arcRedTransmission Values for 6 mm thickSampleWavelength (nm)Transmission (%)300.00.3310.07.5320.030.7330.056.6340.073.6350.083.1360.087.2380.088.8400.090.6450.090.9500.091.4600.091.5Material PropertiesMATERIAL PROPERTIESA74 1-505-298-2550The most well-known low-expansion borosilicate glass (LEBG) is Pyrex made by Corning. It is well suited for applications in which high temperature, thermal shock, or resistance to chemical attack are primary considerations. On the other hand, LEBG is typically less homogeneous and contains more striae and bubbles than optical glasses such as N-BK7. This material is ideally suited to such tasks as mirror substrates, condenser lenses for high-power illumination systems, or windows in high-temperature environments. Because of its low cost and excellent thermal stability, it is the standard material used in test plates and optical fats. The transmission of LEBG extends into the ultraviolet and well into the infrared. The index of refraction in this material varies considerably from batch to batch. Typical values are shown in the accompanying table.Low-Expansion Borosilicate GlassLOW-EXPANSION BOROSILICATE GLASSSpecificationsAbb Constant: 66Knoop Hardness: 480Density: 2.23 g/cm3 @ 25CYoungs Modulus: 5.98x109 dynes/mm2Poissons Ratio: 0.20Specifc Heat: 0.17 cal/g/C @ 25CCoeffcient of Thermal Expansion: 3.25x106/C (0300C)Softening Point: 820CMelting Point: 1250CWavelength in Micrometers.2100Percent ExternalTransmittance80401.0 2.460202.8 .6 .4 .8 2.0 1.4External transmittance for 8 mm thick uncoated low-expansion borosilicate glassLow-Expansion Borosilicate GlassWavelength (nm) Index of Refraction Fraunhofer Designation Source Spectral Region486.11.479FH2 arcBlue514.51.477Ar laserGreen546.11.476eHg arcGreen587.61.474dNa arcYellow643.81.472CCd arcRedMATERIAL PROPERTIESGaussian Beam OpticsLaser GuideMachine Vision GuideFundamental OpticsOptical SpecicationsMaterial PropertiesOptical Coatings & MaterialsA75 marketplace.idexop.comMany optical applications require a substrate material with a near-zero coeffcient of thermal expansion and/or excellent thermal shock resistance. ZERODUR with its very small coeffcient of thermal expansion at room temperature is such a material.ZERODUR, which belongs to the glass-ceramic composite class of materials, has both an amorphous (vitreous) component and a crystalline component. This Schott glass is subjected to special thermal cycling during manufacture so that approximately 75% of the vitreous material is converted to the crystalline quartz form. The crystals are typically only 50 nm in diameter, and ZERODUR appears reasonably transparent to the eye because the refractive indices of the two phases are almost identical.Typical of amorphous substances, the vitreous phase has a positive coeffcient of thermal expansion. The crystalline phase has a negative coeffcient of expansion at room temperature. The overall linear thermal expansion coeffcient of the combination is almost zero at useful temperatures.The fgure below shows the variation of expansion coeffcient with temperature for a typical sample. The actual performance varies very slightly, batch to batch, with the room temperature expansion coeffcient in the range of 0.15x10-6/C. By design, this material exhibits a change in the sign of the coeffcient near room temperature. A comparison of the thermal expansion coeffcients of ZERODUR and fused silica is shown in the fgure. ZERODUR is markedly superior over a large temperature range, and consequently, makes ideal mirror substrates for such stringent applications as multiple-exposure holography, holographic and general interferometry, manipulation of moderately powerful laser beams, and space-borne imaging systems.ZERODURZERODURSpecificationsAbb Constant: 66Dispersion: (nFnC) = 0.00967Knoop Hardness: 620Density: 2.53 g/cm3 @ 25CYoungs Modulus: 9.1x109 dynes/mm2Poissons Ratio: 0.24Specifc Heat: 0.196 cal/g/CCoeffcient of Thermal Expansion:0.0580.10x106/ (20300C)Maximum Temperature: 600CRefractive Index of ZERODURWavelength (nm)Index of Refraction Fraunhofer Designation435.81.5544g480.01.5497F486.11.5491F546.11.5447e587.61.5424d643.81.5399C656.31.5394CMaterial PropertiesMATERIAL PROPERTIESA76 1-505-298-2550Infrasil 302 is an optical-quality quartz glass made by fusing natural quartz crystals in an electric oven. It combines excellent physical properties with excellent optical characteristics, especially in the near infrared region (1 to 3 m) because it does not exhibit the strong OH absorption bands typical of synthetic fused silica.Infrasil 302 is homogeneous in the primary functional direction. Weak striations, if any, are parallel to the major faces and do not affect optical performance.Infrasil 302INFRASIL 302SpecificationsOH content: