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Fundamental Optics Internal Transmittance of Five Schott Glass Types Internal Transmittance (%) Wavelength l BK7 Thickness (mm) SF11 Thickness (mm) LaSFN9 Thickness (mm) BaK1 Thickness (mm) F2 Thickness (mm) (nm) 5 25 5 25 5 25 5 25 5 25 Material Properties Optical Specifications Gaussian Beam Optics 300 310 320 330 340 350 360 370 380 390 400 420 440 460 480 500 540 580 620 660 700 0.26 0.59 0.81 0.91 0.96 0.986 0.991 0.995 0.996 0.998 0.998 0.998 0.999 0.999 0.999 0.999 0.999 0.999 0.999 0.999 0.999 — 0.07 0.35 0.65 0.83 0.93 0.96 0.974 0.980 0.989 0.991 0.993 0.994 0.994 0.995 0.996 0.996 0.996 0.997 0.997 0.998 — — — — — — — — 0.13 0.46 0.73 0.93 0.97 0.986 0.991 0.995 0.998 0.998 0.998 0.999 0.999 — — — — — — — — — 0.02 0.21 0.69 0.86 0.93 0.95 0.976 0.988 0.992 0.992 0.993 0.994 — — — — — — — 0.55 0.70 0.80 0.86 0.92 0.94 0.96 0.972 0.980 0.990 0.995 0.996 0.997 0.997 — — — — — — — 0.05 0.18 0.34 0.47 0.66 0.76 0.83 0.87 0.91 0.95 0.975 0.983 0.986 0.990 0.64 0.81 0.89 0.94 0.97 0.981 0.990 0.995 0.996 0.997 0.998 0.998 0.998 0.998 0.998 0.998 0.999 0.999 0.999 0.999 0.999 0.11 0.34 0.56 0.73 0.84 0.91 0.95 0.976 0.982 0.987 0.988 0.989 0.989 0.990 0.991 0.991 0.993 0.994 0.995 0.996 0.997 — — — — 0.81 0.95 0.973 0.987 0.992 0.995 0.996 0.997 0.998 0.998 0.999 0.999 0.999 0.999 0.999 0.999 0.999 — — — — 0.42 0.78 0.87 0.94 0.96 0.973 0.982 0.987 0.989 0.991 0.992 0.993 0.995 0.995 0.995 0.995 0.996 Optical Coatings 4.10 1 Visit Us OnLine! www.mellesgriot.com
Synthetic Fused Silica Fused silica is an ideal optical material for many applications. It is transparent over a wide spectral range, has a low coefficient of thermal expansion, and is resistant to scratching and thermal shock. Synthetic fused silica (amorphous silicon dioxide) is formed by chemical combination of silicon and oxygen. It is not to be confused with fused quartz, which is made by crushing and melting natural crystals, or by fusing silica sand, which results in a granular microstructure and bubble entrapment. Microstructure and impurities lead to local index variations and contribute, along with bubbles and opaque particles, to reduced transmission throughout the spectrum. Synthetic fused silica is far purer than fused quartz. This increased purity ensures higher ultraviolet transmission and freedom from striae or inclusions. The synthetic fused-silica materials used by Melles Griot are manufactured by flame 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. Controlling the purity of reactants and the conditions of reaction ensures the high quality of the synthetic fused silica from which our lenses are made. Synthetic fused-silica lenses offer a number of advantages over glass or fused quartz: $ Greater ultraviolet and infrared transmission $ Low coefficient of thermal expansion, which provides stability and resistance to thermal shock over large temperature excursions $ Wider thermal operating range $ Increased hardness and resistance to scratching $ Much higher resistance to radiation darkening from ultraviolet, X-rays, gamma rays, and neutrons. Optical-quality synthetic fused silica (OQSFS) lenses are ideally suited for applications in energy-gathering and imaging systems in the mid-ultraviolet, visible, and near-infrared spectral regions. The low dispersion of fused silica reduces chromatic aberration. UV-grade synthetic fused silica (UVGSFS) is selected to offer the highest transmission (especially in the deep ultraviolet) and very low fluorescence levels (approximately 0.1% that of fused natural quartz excited at 254 nm). UV-grade synthetic fused silica does not fluoresce 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 specifications. The left-hand table on page 4.13 shows the refractive index of a typical UV-grade synthetic fused silica versus wavelength at 20ºC. To obtain the index for optical-quality synthetic fused silica, round the values off to the fourth decimal place. Glass transmittances are affected by thermal history after manufacture, as well as during the manufacturing process. Depending on the manufacturer and subsequent thermal processing (coating, annealing, or tempering), it is possible for any optical glass, including BK7, to show internal transmittance reductions of several percent across the entire spectrum with external transmittance correspondingly affected. Transmittance of all glass is especially uncertain at wavelengths approaching the water absorption band at 2.7 mm. Synthetic fused silica also shows batch-to-batch transmittance variations, especially in deep ultraviolet and infrared. These variations are related to manufacture and impurity content rather than subsequent history. In the ultraviolet, these variations have been attributed to uncontrollable fluctuations in metallic impurity content at the parts per billion level. Ultraviolet transmittance is the basis for the classifications UV grade and optical quality. A specification of UV grade ensures that a specimen is represented by the broadest curve. Transmittance curves for optical quality may fall anywhere between the UVGSFS curve and the OQSFS curve shown in figure 4.1. Infrared batch-to-batch transmittance variations in synthetic fused silica are attributable to fluctuations in the OH chemical bond content. These variations are most pronounced at wavelengths near and beyond the water absorption band at 2.7 mm and are normally uncontrolled because ultraviolet transmittance is generally regarded as more important. High infrared transmittance can be ensured by appropriate manufacturing controls, but only at the sacrifice of ultraviolet transmittance. Visible spectrum batch-to-batch transmittance variations in synthetic fused silica are insignificant. The high ultraviolet internal transmittance of UV-grade synthetic fused silica is correlated with a visible internal transmittance that is so high it is beyond traditional methods of measurement. It is necessary to measure optical signal attenuation in fibers drawn of the material. Figure 4.2 shows a semilogarithmic comparison of the internal transmittances of UV-grade synthetic fused silica and BK7 glass. It is evident from this graph that UV-grade synthetic fused silica averages about two orders of magnitude less absorption loss than BK7 across the visible spectrum. In a sample thickness of 10 mm, the internal transmittance of UV-grade synthetic fused silica differs from unity only in the fifth decimal place. The high internal transmittance of such a material can be exploited by maintaining the optic at Brewster’s angle for the appropriate linear polarization, or with the assistance of high-efficiency antireflection coatings such as HEBBAR or one of the laser line V-coats. With these coatings it is possible to achieve external transmittances of 98.5% and 99.5%, respectively. Synthetic fused silica and HEBBAR are especially well suited to each other in visible spectrum applications. Fundamental Optics Gaussian Beam Optics Optical Specifications Material Properties Optical Coatings Visit Us Online! www.mellesgriot.com 1 4.11
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 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: Refractive Index of Five Schott Gla
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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