Optical Coatings

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Fundamental Optics Material Properties Optical Specifications Gaussian Beam Optics PARTIALLY TRANSMITTING COATINGS In many applications, it is desirable to split a beam of light into two components with an arbitrary intensity ratio. This is performed by inserting an optical surface at some oblique angle (usually 45 degrees) to produce a separate reflected and transmitted component. In most cases, a multilayer coating is applied to the surface in order to modify intensity and polarization ratios of the two beams. An alternative to the outdated metallic beamsplitter is a broadband (or narrowband) multilayer dielectric stack with a limited number of pairs of layers, which transmits a fixed amount of the incident light. Just as in the case of metallic beamsplitter coatings, the ratio of reflected and transmitted beams depends on the angle of incidence. Since the angle of incidence is normally fixed at 45 degrees, this does not present a significant problem. Unlike a metallic coating, a high-quality film will introduce negligible losses by either absorption or scattering. There are, however, two drawbacks to dielectric beamsplitters. The performance of these coatings is more wavelength sensitive than that of metallics, and the ratio of transmitted and reflected intensities may be quite different for the s- and p-polarization components of the incident beam. In polarizers, this can be used to advantage. The difference in partial polarization of the reflected and transmitted beams is not important, particularly where polarized lasers are used. In beamsplitters, this is usually a drawback. A hybrid metal-dielectric coating is often the best compromise. Melles Griot produces coated beamsplitters with designs ranging from broadband performance without polarization compensation, to broadband with some compensation for polarization, to a completely new range of cube beamsplitters that are virtually nonpolarizing at certain laser wavelengths. These nonpolarizing beamsplitters offer unparalleled performance with the reflected s- and p-components matched to better than 5%. Optical Coatings 5.32 1 Visit Us OnLine! www.mellesgriot.com
MAXBRIte Coatings MAXBRIte (multilayer all-dielectric xerophilous broadband reflecting interference) coatings are, without a doubt, the best broadband mirror coatings commercially available. The /001 coating covers the visible spectrum from 480 nm to 700 nm, the /003 is useful for diode laser applications from 630 nm to 850 nm, and the /009 coating offers enhanced blue response. They all reflect well over 98% of incident laser radiation within their respective wavelength ranges. These coatings exhibit exceptionally high reflectances for both s- and p-polarizations. In each case, at the most important laser wavelengths and for angles of incidence as high as 45 degrees, the average of s- and p-reflectances exceeds 99%. For most applications, they are superior to metallic or enhanced metallic coatings. The /001 MAXBRIte coating (figure 5.44) is suitable for instrumental and external laser-beam manipulation tasks. It is the ideal choice for use with tunable dye and parametric oscillator systems. The structural design of this coating is such that flatness specifications as tight as l/10 can be maintained using low-expansion substrate materials. The /003 MAXBRIte coating (figure 5.45) covers all the important diode laser wavelengths from 630 to 850 nm; therefore, it can be used with both visible and near-infrared diode lasers. This broadband coating is ideal for applications employing nontemperature- stabilized diode lasers where wavelength drift is likely to occur. The /003 also makes it possible to use a HeNe laser to align diode systems. The /007 ultraviolet MAXBRIte coating (figure 5.46) offers superior performance for ultraviolet applications. It is ideal for use with many of the excimer lasers, as well as the third and fourth harmonics of most solid-state lasers. It is also particularly useful with broadband ultraviolet light sources, such as mercury and xenon lamps. Due to mechanical stresses within this intricate coating, it is limited to substrates of l/4 figure or less. The /009 extended MAXBRIte coating (figure 5.47) offers superior response below 500 nm, and it is particularly useful for helium cadmium lasers at 442 nm, or the blue lines of argon-ion lasers. Like the /007, mechanical stresses in this complex coating limit its use to substrates of l/4 figure or less. Because of the many applications for these superior coatings we stock a number of precoated substrates. MAXBRIte Coatings Wavelength Range (nm) 480–700 630–850 245–390 420–700 Average Reflectance (%) 98 98 98 98 Angle of Incidence (degrees) 0±45 0±45 0±45 0±45 Note: To order, append coating suffix to product number. COATING SUFFIX /001 /003 /007 /009 PERCENT REFLECTANCE PERCENT REFLECTANCE 100 99 98 97 96 100 99 98 97 96 normal incidence 45° incidence 500 600 700 800 WAVELENGTH IN NANOMETERS Figure 5.44 MAXBRIte /001 coating normal incidence 45° incidence 600 700 800 900 WAVELENGTH IN NANOMETERS typical reflectance curves $ Exceptional reflectance for s- and p- polarization $ Excellent performance for common visible lines $ Suitable for external laser-beam manipulation and many instrument applications $ R avg > 98% from 480 to 700 nm $ Damage threshold: 0.92 J/cm 2 810%, 10-nsec pulse (57 MW/cm 2 ) at 532 nm Figure 5.45 MAXBRIte /003 coating typical reflectance curves $ Useful with visible, near-infrared diode, and HeNe lasers $ Easily accommodates diode wavelength drift $ Ideal for pointing and alignment applications $ R avg > 98% from 630 to 850 nm $ Damage threshold: see /001 (similar specifications) Fundamental Optics Gaussian Beam Optics Optical Specifications Material Properties Optical Coatings Visit Us Online! www.mellesgriot.com 1 5.33
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Fundamental Optics 1 Introduction 1
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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
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Lens Shape Aberrations described in
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ay f-numbers 2.7 3.3 4.4 6.7 13.3 S
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AIRY DISC DIAMETER = 2.44 l f/# Fig
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Lens Selection Having discussed the
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Example 4: Diffraction-Limited Perf
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Aberration Balancing To improve sys
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Definition of Terms FOCAL LENGTH (f
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infinity (which is a comfortable vi
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For symmetric lenses (r 2 = 4r 1 ),
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Separation of Nodal Point from Corr
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Gaussian Beam Optics 2 Introduction
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Even if a Gaussian TEM 00 laser-bea
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eam expander INCORPORATING M 2 INTO
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M 2 AND THE LENS EQUATION For real-
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employed when laser power must be c
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Figure 2.13 Keplerian beam expander
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Optical Specifications 3 Wavefront
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Centration The mechanical axis and
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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 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: PERCENT REFLECTANCE 100 80 60 40 20
Page 109 and 110: Laser-Line MAX-R Coatings These mu
Page 111 and 112: Ultrafast Coating Melles Griot has
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