Optical Coatings

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Fundamental Optics Material Properties Overview Material Usable Transmission Range Index of Refraction Features BK7 BK7 1.52 @ 0.55 mm Excellent all-around lens material provides broad transmission with excellent mechanical characteristics Material Properties Optical Specifications Gaussian Beam Optics LaSFN9 SF11 F2 BaK1 Optical-Quality Synthetic Fused Silica (OQSFS) UV-Grade Synthetic Fused Silica (UVGSFS) Optical Crown Glass Low-expansion borosilicate glass LEBG Sapphire Zinc Selenide Calcium Fluoride LaSFN9 SF11 F2 BaK1 OQSFS UVGSFS OPTICAL CROWN LEBG SAPPHIRE ZINC SELENIDE CALCIUM FLUORIDE 1.86 @ 0.55 mm 1.79 @ 0.55 mm 1.62 @ 0.55 mm 1.57 @ 0.55 mm 1.46 @ 0.55 mm 1.46 @ 0.55 mm 1.52 @ 0.55 mm 1.48 @ 0.55 mm 1.77 @ 0.55 mm 2.40 @ 10.6 mm 1.399 @ 5 mm High-refractive-index flint glass provides more power with less curvature needed High-refractive-index flint glass provides more power with less curvature needed Material represents a good compromise between higher index and acceptable mechanical characteristics Excellent all-around lens material, but has weaker chemical characteristics than BK7 Material provides good UV transmission and superior mechanical characteristics Material provides excellent UV transmission and superior mechanical characteristics This lower tolerance glass can be used as a mirror substrate or in noncritical applications Excellent thermal stability, low cost, and homogeneity makes LEBG useful for high-temperature windows, mirror substrates, and condenser lenses Excellent mechanical and thermal characteristics make it a superior window material Zinc selenide is most popular for transmissive IR optics, transmits visible and IR, and has low absorption in the red end of the spectrum This popular UV excimer laser material is used for windows, lenses, and mirror substrates 0.1 0.5 1.0 5.0 10.0 WAVELENGTHS IN mm Optical Coatings 4.2 1 Visit Us OnLine! www.mellesgriot.com
Introduction Glass manufacturers provide hundreds of different glass types with differing optical transmissibility and mechanical strengths. Melles Griot has simplified the task of selecting the right material for an optical component by offering each of our standard components in 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 specific information to select a material for a custom component. The information given in this chapter is intended to help those in such situations. The most important material properties to consider in regard to an optical element are as follows: $ Transmission versus wavelength $ Index of refraction $ Thermal characteristics $ Mechanical characteristics $ Chemical characteristics $ Cost. Transmission versus Wavelength A material must be transmissive at the wavelength of interest if it is to be used for a transmissive component. A transmission curve allows the optical designer to estimate the attenuation of light, at various wavelengths, caused by internal material properties. For mirror substrates, the attenuation may be of no consequence. Index of Refraction The index of refraction, as well as the rate of change of index 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 flint glasses have higher dispersions, resulting in more chromatic aberration in polychromatic applications. They also typically have poorer chemical characteristics than lower index crown glasses. Thermal Characteristics The thermal expansion coefficient 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 Characteristics The mechanical characteristics of a material are significant 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 Characteristics The 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. Cost Cost is almost always a factor to consider when specifying materials. Furthermore, the cost of some materials, such as UVgrade synthetic fused silica, increases sharply with larger diameters because of the difficulty in obtaining large pieces of the material. Fundamental Optics Gaussian Beam Optics Optical Specifications Material Properties Optical Coatings Visit Us Online! www.mellesgriot.com 1 4.3
Page 1 and 2:
Fundamental Optics 1 Introduction 1
Page 3 and 4:
Paraxial Formulas SIGN CONVENTIONS
Page 5 and 6:
object F 2 Figure 1.4 image Example
Page 7 and 8: Figure 1.6 Figure 1.7 f f 2 object
Page 9 and 10: Figure 1.8 Figure 1.9 INDIVIDUAL EL
Page 11 and 12: Performance Factors After paraxial
Page 13 and 14: third-order, monochromatic, spheric
Page 15 and 16: Positive lens elements usually have
Page 17 and 18: Lens Shape Aberrations described in
Page 19 and 20: ay f-numbers 2.7 3.3 4.4 6.7 13.3 S
Page 21 and 22: AIRY DISC DIAMETER = 2.44 l f/# Fig
Page 23 and 24: Lens Selection Having discussed the
Page 25 and 26: Example 4: Diffraction-Limited Perf
Page 27 and 28: Aberration Balancing To improve sys
Page 29 and 30: Definition of Terms FOCAL LENGTH (f
Page 31 and 32: infinity (which is a comfortable vi
Page 33 and 34: For symmetric lenses (r 2 = 4r 1 ),
Page 35 and 36: Separation of Nodal Point from Corr
Page 37 and 38: Gaussian Beam Optics 2 Introduction
Page 39 and 40: Even if a Gaussian TEM 00 laser-bea
Page 41 and 42: eam expander INCORPORATING M 2 INTO
Page 43 and 44: M 2 AND THE LENS EQUATION For real-
Page 45 and 46: employed when laser power must be c
Page 47 and 48: Figure 2.13 Keplerian beam expander
Page 49 and 50: Optical Specifications 3 Wavefront
Page 51 and 52: Centration The mechanical axis and
Page 53 and 54: PERFECT RECTANGULAR LENS The MDMTF
Page 55 and 56: The permissible number of maximum-s
Page 57: Material Properties 4 Material Prop
Page 61 and 62: maximum value for homogeneity withi
Page 63 and 64: Melles Griot Lens Materials Melles
Page 65 and 66: Refractive Index of Five Schott Gla
Page 67 and 68: Synthetic Fused Silica Fused silica
Page 69 and 70: PERCENT INTERNAL TRANSMITTANCE 99.9
Page 71 and 72: Low-Expansion Borosilicate Glass Th
Page 73 and 74: ZERODUR ® Many optical application
Page 75 and 76: Optical Coatings 5 Optical Coatings
Page 77 and 78: OEM and Special Coatings Melles Gri
Page 79 and 80: PERCENT REFLECTANCE 100 90 80 70 60
Page 81 and 82: will depend on the ratio of optical
Page 83 and 84: v = angle of incidence PERCENT REFL
Page 85 and 86: PERCENT REFLECTANCE PER SURFACE 2.0
Page 87 and 88: Two-Layer Coatings of Arbitrary Thi
Page 89 and 90: ION-ASSISTED BOMBARDMENT Ion-assist
Page 91 and 92: Single-Layer MgF 2 Antireflection C
Page 93 and 94: PERCENT REFLECTANCE 5 4 3 2 1 norma
Page 95 and 96: EXTENDED-RANGE HEBBAR ANTIREFLECTIO
Page 97 and 98: V-Coatings V-coatings are multilaye
Page 99 and 100: Metallic High-Reflection Coatings W
Page 101 and 102: INTERNAL SILVER (/036) $ For intern
Page 103 and 104: Dielectric High-Reflection Coatings
Page 105 and 106: PERCENT REFLECTANCE 100 80 60 40 20
Page 107 and 108: MAXBRIte Coatings MAXBRIte (multi
Page 109 and 110:
Laser-Line MAX-R Coatings These mu
Page 111 and 112:
Ultrafast Coating Melles Griot has
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Optical Coatings

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