Optical Coatings

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Fundamental Optics Material Properties Optical Specifications Gaussian Beam Optics Optical Crown Glass In 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 BK7. Optical crown is suitable for applications in which component tolerances are fairly loose and as a substrate material for mirrors. Transmittance characteristics for optical crown are shown in figure 4.3. Relevant properties of optical crown are shown in the accompanying table. OPTICAL CROWN GLASS CONSTANTS Glass Type Designation: B270 Abbé Constant: v d = 58.5 Dispersion: (n F 4 n C ) = 0.0089 Density: 2.55 g cm 43 at 23°C Young’s Modulus: 71.5 kN/mm 2 Specific Heat: C p (20º to 100°C) = 0.184 cal/g°C Coefficient of Linear Expansion (20º to 300°C): 93.3 ! 10 47 /°C Transformation Temperature: 521°C Softening Point: 708°C PERCENT EXTERNAL TRANSMITTANCE 100 90 80 70 60 50 40 30 20 10 Refractive Index of Optical Crown Glass Wavelength (nm) Refractive Index, n Fraunhofer Designation Source Spectral Region 435.8 480.0 486.1 546.1 587.6 589.0 643.8 656.3 1.53394 1.52960 1.52908 1.52501 1.52288 1.52280 1.52059 1.52015 g F′ F e d D C′ C Hg arc Cd arc H 2 arc Hg arc He arc Na arc Cd arc H 2 arc Blue Blue Blue Green Yellow Yellow Red Red Transmission Values for 6-mm-thick Sample 300 nm = 0.3% 310 nm = 7.5% 320 nm = 30.7% 330 nm = 56.6% 340 nm = 73.6% 350 nm = 83.1% 360 nm = 87.2% 380 nm = 88.8% 400 nm = 90.6% 450 nm = 90.9% 500 nm = 91.4% 600 nm = 91.5% Note: Transmission in visible region (including reflection loss) = 91.7% (t = 2 mm). 300 400 500 1000 2000 3000 Optical Coatings Figure 4.3 WAVELENGTH IN NANOMETERS External transmittance for 10-mm-thick uncoated optical crown glass 4.14 1 Visit Us OnLine! www.mellesgriot.com
Low-Expansion Borosilicate Glass The 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 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 flats. As seen in figure 4.4, 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 GLASS CONSTANTS Abbé Constant: v d = 66 Density: 2.23 g cm 43 at 25°C Young’s Modulus: 5.98 !10 9 dynes/mm 2 Poisson’s Ratio: 0.20 Specific Heat at 25ºC: 0.17 cal/g°C Coefficient of Linear Expansion (0° to 300°C): 3.25!10 46 /°C Softening Point: 820°C Melting Point: 1250°C Pyrex ® is a registered trademark of Corning, Inc. PERCENT EXTERNAL TRANSMITTANCE 100 80 60 40 20 0 .2 .4 .6 .8 1 1.4 WAVELENGTH IN MICROMETERS 2 2.4 2.8 Figure 4.4 External transmittance for 8-mm-thick uncoated low-expansion borosilicate glass Refractive Index of Low-Expansion Borosilicate Glass Wavelength (nm) 486.1 514.5 546.1 587.6 643.8 Refractive Index, n 1.479 1.477 1.476 1.474 1.472 Fraunhofer Designation F e d C′ Source H 2 arc Ar laser Hg arc Na arc Cd arc Spectral Region Blue Green Green Yellow Red Fundamental Optics Gaussian Beam Optics Optical Specifications Material Properties Optical Coatings Visit Us Online! www.mellesgriot.com 1 4.15
Page 1 and 2:
Fundamental Optics 1 Introduction 1
Page 3 and 4:
Paraxial Formulas SIGN CONVENTIONS
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object F 2 Figure 1.4 image Example
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Figure 1.6 Figure 1.7 f f 2 object
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Figure 1.8 Figure 1.9 INDIVIDUAL EL
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Performance Factors After paraxial
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third-order, monochromatic, spheric
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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 and 58: Material Properties 4 Material Prop
Page 59 and 60: Introduction Glass manufacturers pr
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: PERCENT INTERNAL TRANSMITTANCE 99.9
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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