1 / 36

Jean-Marie MACKOWSKI Université Claude Bernard Lyon 1 SMA-VIRGO Bât 213 22, Bd Niels Bohr

Jean-Marie MACKOWSKI Université Claude Bernard Lyon 1 SMA-VIRGO Bât 213 22, Bd Niels Bohr 69622 Villeurbanne Cedex mackowski@ipnl.in2p3.fr Phone : + 33 04 72 43 26 69 Fax : + 33 04 78 89 19 36. TODAY MENU. COATING DEFINITION DIELECTRIC COATINGS Quaterwave Rule Some Useful Designs

miyoko
Download Presentation

Jean-Marie MACKOWSKI Université Claude Bernard Lyon 1 SMA-VIRGO Bât 213 22, Bd Niels Bohr

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Jean-Marie MACKOWSKI Université Claude Bernard Lyon 1 SMA-VIRGO Bât 213 22, Bd Niels Bohr 69622 Villeurbanne Cedex mackowski@ipnl.in2p3.fr Phone : + 33 04 72 43 26 69 Fax : + 33 04 78 89 19 36

  2. TODAY MENU COATING DEFINITION DIELECTRIC COATINGS Quaterwave Rule Some Useful Designs METALLIC COATINGS Silver, Aluminum, Gold Reflectors Passivation Layers Antireflection of a Metal Enhanced reflectors by Dielectric Layers TOMORROW MENU Coatings Deposition techniques Performances & limitations

  3. OPTICAL COATINGS 2. Incident Reflected Coating Surface Transmitted Optical coating consist of a layer or series of layers of different materials, that are deposited over the surface to be treated. The desired properties of the coating are achieved by a mixture of interference and intrinsic properties of the materials that are used

  4. COATINGS INCLUDING DIELECTRIC LAYERS ONLY

  5. WHY THIN AND NOT THICK FILMS ? Using interference properties means creating and changing the shape of interference fringes Transmittance (%) 97.5 Thick materials Give fringes too Closely spaced To be useful 97.0 96.5 Glass 100 µm 96.0 95.5 400 500 600 700 Wavelength (nm) Transmittance (%) Thin films Give The desirable Broad fringes That we need 97.5 97.0 96.5 Glass 1 µm 96.0 95.5 400 500 600 700 Wavelength (nm)

  6. BASIC DESIGN PRINCIPLES Quaterwave Layers give Maximum interference Effect Half Layers are Absentee Layers-They have No Effect Dielectric Layers Become Weaker whit Increasing Wavelenght Metal Layers become Stronger with Increasing Wavelenght

  7. transforms the surface following the rule : A quarter stack with x layers of H and (x-1) layers of L: has reflectance THE QUATERWAVE RULE A quarterwave: is the working wavelenght are the refractive indexes of film, transformed surface, and substrat, respectively

  8. THE QUATERWAVE RULE ... Interference calculations for two waves are very simple when the waves are combined Are exactly in phase or exactly out of phase. In the former case the resultant amplitude Is simply given by the sum of individual amplitudes while in the latter it is the difference of amplitudes. All others cases are intermediate. The phase shift on reflection at a simple interface between two dielectric media is either Zero or 180° (  / 2). The phase shift suffered by a wave traveling through thickness d of a thin film is given by - 2  n /  The minus sign indicates a phase lag. This is such an important quantity that its magnitude is given the symbol :  =2  n d / 

  9. l/2 n0-n1 n0+n1 <0 n1-n2 n1+n2 > 0 REFLECTION OF SINGLE FILM d: l/2= l/4+0+l/4 l/2 Amplitude reflectance of light: air no n1> no Thin film 0 n2< n1 Substrate Reflected light: Beams interfere constructively Film Thickness is Quaterwave

  10. d: l/2  = l /4+ l / 2 +l /4 l/2 l/2 n0-n1 n0+n1 <0 n1-n2 n1+n2 < 0 ANTIREFLECTION OF SINGLE FILM l /4 Thin film thickness = air no Beams interfere destructively Amplitude reflectance of light: n1> no Thin film n2> n1 Substrate Reflection =0 ifno / n1 = n1 / n2n1= (non2)1/2

  11. no no nH> no nH> no high index nL< nH nL< nH low index nH> nL nH> nL high index nL< nH nL< nH low index nH> nL nH> nL high index nS< nH nS< nH Substrate DIELECTRIC MIRRORS Beams interfere constructively d:l /2 l /2 3l /2 3l /2 5l /2 5l /2 air l/2 0 l/2 0 l/2 0

  12. QUATERWAVE STACK IS A BASIC BUILDING BLOCK 23-Layer quaterwave stack centered on 800 nm Ripple Transmittance (%) 100 80 Notch Filter 60 Longwave pass or Dichroic Filter 40 Shortwave pass or Dichroic Filter 20 0 High Reflectance 200 400 600 800 1000 1200 1400 Wavelength (nm) The ripple is usually removed by adding several layers at each end and refining them into a matching structure

  13. RIPPLE CONTROL 23-Layer quaterwave stack centered on 800 nm Without Ripple control Transmittance (%) 100 80 60 40 20 0 200 400 600 800 1000 1200 1400 Wavelength (nm) 23-Layer quaterwave stack centered on 800 nm With Ripple control (Matching Layers) Quaterwave stack L (HL)^11 E.M Quaterwave stack L (HL)^11 E.M I.M E.M (2L.1H)^2 (.1H2L)^2

  14. BROADBAND REFLECTOR Reflectance (%) 100 80 60 (HL)^5 1.2L (1.4H 1.4L)^5 1.4H 40 20 0 350 400 450 500 550 600 650 700 750 800 850 900 950 1000 Wavelength (nm) Reflectance (%) 100 H index : 2.35 ZnS L index : 1.35 Cryolite :Na3ALF6 98 96 94 23 Layers 92 90 350 400 450 500 550 600 650 700 750 800 850 900 950 1000 Wavelength (nm)

  15. MULTIPLE-CAVITY FILTER Transmittance (%) 100 80 Three-cavity 60 40 Two-cavity Single cavity 20 0 990 995 1000 1005 1010 Wavelength (nm) A simple cavity consists of a half wave layer surrounded by to reflectors This gives a narrow band of transmission. Better pass band can be achieved by coupling cavities into multiple-cavity filters Here a three cavity: {(HL)^5 HH (LH)^5}^3 giving a band pass of 1.2 nm.

  16. OBLIQUE INCIDENCE At oblique incidence the path difference between the beams is reduced and their amplitudes for s-polarized light is increased and for p-polarized light decreased. Characteristics move To shorter Wavelenght and become @ 45° of incidence : Stronger for s-polarization And weaker for p-polarization The green curve is given at Normal incidence. Transmittance (%) 100 R 80 60 40 20 G B 0 300 400 500 600 Wavelength (nm)

  17. WIDE-ANGLE ANTIREFLECTION COATING Reflectance (%) s-Polarization p-Polarization 5 4 3 2 1 0 0 10 20 30 40 50 60 70 Incident Angle (deg) Here an antireflection coating on glass for a single wavelenght (510 nm) At angles of incidence up to 5O° and both polarizations. 9 layers of MgF2, Al2O3 and TiO2

  18. NON-POLARIZING BEAM SPLITTER Reflectance (%) 60 40 20 0 500 600 Wavelength (nm) The design of dielectric coatings to have equal p- and s-polarization over a large spectral region is exceptionally difficult. Here a simple 8 layers 45° beam splitter for 500 to 600 nm using TiO2, Al2O3 and SiO2

  19. Lx, Hz (HL)^10 Stack Performances Transmittance (%) 100 80 L (HL)^10 H (HL)^10 LL (HL)^10 60 40 20 0 400 500 600 700 Wavelength (nm)

  20. ELECTRIC FIELD DISTRIBUTION ALL LAYERS Electric Field (V/m) 60 L (HL)^10 H (HL)^10 LL (HL)^10 40 20 -1 0 1 2 3 4 5 6 Design2: Parallel Electric Field THE FIRST LAYERS OF ALL DESIGNS Optical Distance from Medium Electric Field (V/m) 60 40 20 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 Optical Distance from Medium

  21. Total Layer Absorptance (%) 0.0005 0.0004 0.0003 0.0002 0.0001 0.0000 1 2 3 4 5 7 8 9 10 20 6 11 12 13 14 15 16 17 18 19 COMPONENT ABSORPTION VS DESIGN l0 = 800 nm L(HL)^10 H(HL)^10 LL(HL)^10 Layer number Total Layer Absorptance (%) l0 = 550 nm 0.00008 0.00007 0.00006 0.00005 0.00004 0.00003 0.00002 0.00001 0.00000 Layer number 1 2 3 4 5 7 8 9 10 20 6 11 12 13 14 15 16 17 18 19

  22. L(HL)^10 R=800 nm, C=550 nm

  23. H(HL)^10 B=800 nm,C=550 nm

  24. LL(HL)^10 G=800 nm,C=550 nm

  25. MULTIDIELECTRIC MIRRORS • Advantages : - High reflectance (> 99.9 %) - Low absorption loss (Visible, IR : < 10 ppm) • Drawbacks : - Multilayers (HL) x HLL (> 30 layers, deposition time long) - High reflectance over a short wavelength domain ( = 250 nm) 100 6 layers 90 14 layers 26 layers 80 70 60 Reflectance (%) 50  =  . 0 .  40 30 20 0 10 0 700 800 900 1000 1100 1200 1300 1400 Wavelength (nm)

  26. COATINGS INCLUDING METALLIC LAYERS The most popular in Astronomy

  27. 100 nm of Silver (R), Aluminum (G), Gold (B) on glass Reflectance (%) 100 80 60 40 20 0 0 2000 4000 6000 8000 10000 Wavelength (nm)

  28. 100 nm of Silver (R), Aluminum (G), Gold (B) on glass Reflectance (%) 100 80 60 40 20 0 0 200 400 600 800 1000 1200 1400 1600 1800 2000 Wavelength (nm)

  29. 100 nm of Silver (R), Aluminum (G), Gold (B) on glass Reflectance (%) 100.0 99.5 99.0 98.5 98.0 97.5 6000 7000 8000 9000 10000 Wavelength (nm)

  30. REFLECTANCE OF A METAL FILM WITH PASSIVATION LAYER BULK METAL b Reflectance (%) SiO2-QW/Ag-100 nm/SIO2-Qw a 100 Ag-100 nm 80 60 40 20 0 0 1000 2000 3000 4000 DIELECTRIC Layer (QW) B Wavelength (nm)

  31. ANTIREFLECTION OF A METAL FILM a b Cr - 10 nm on glass Reflectance (%) 60 Reflector 40 Dielectric phase Matching layer 20 0 400 500 600 700 Metal layer Wavelength (nm) Cr 10 nm / MgF2 100 nm / Al 3 nm

  32. Metal layer High index Low index V INDUCED TRANSMISSION IN A METAL FILM Reflectance (%) 100 80 (HL)^3-M-(LH)^3 60 40 20 0 200 400 600 800 1000 1200 1400 1600 1800 2000 Wavelength (nm)

  33. Enhanced 100 nm of aluminum protected by dielectric layers L (low index) : SiO2 or MgF2 & H (high index) : TiO2 Reflectance (%) 100 Al+(H L)^3 98 Al+(H L)^3 96 94 Al+(H L)^2 92 Al+H L 90 Al 88 86 340 360 380 400 420 440 460 480 500 520 540 Wavelength (nm)

  34. Enhanced 100 nm of aluminum protected by dielectric layers L (low index) : SiO2 , H (high index) : TiO2 Reflectance (%) 100 95 90 Al+(HL)^20 T=99,54% Al+(HL)^3 R=99,57% 85 80 75 70 340 360 380 400 420 440 460 480 500 520 540 Wavelength (nm)

  35. METALLIC MIRRORS • Advantages : High reflectance (> 90 %) - over a large range of incident angles - over a wide band of wavelength (UV, Visible, IR) • Drawback : High absorption loss Al : good for U.V. (R > 90 %), adhere on most substrates, passivation necessary (oxidation) Ag : most popular, easy to deposit, highest reflectance in visible and I.R., tarnish rapidly, protection necessary Au : best material in I.R. (> 700 nm), high reflectance, does not tarnish Al Au Ag

More Related