Paper and Progress Report

Artoni Kevin R. Ang

July 1, 2009

Progress Report

• Changed substrate holder

• Added a new pair of electrodes and boat holder

Progress Report

• Coated Cr-Cu-Cr mirror (4 designs)

• Measured transmission of the Cr-Cu-Cr coatings using the Ocean Optics Spectrophotometer

Slide 1

  Exp (nm) Theo (nm) Error (%)

Air      

Cr 7.2 5 44

Cu 199 200 0.5

Cr 8 5 60

Glass Slide      

Slide 1

Experimental Transmission

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Wavelength (nm)

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ns

mis

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14-May

19-May

20-May

Slide 1

Theoretical Transmission

0

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Wavelength (nm)

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TheoreticalTransmission

Slide 2

  Exp (nm) Theo (nm) Error (%)

Air      

Cr 6.8 5 36

Cu 98 100 2

Cr 7.1 5 42

Glass Slide      

Slide 2

Experimental Transmission

01020304050607080

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Wavelength (nm)

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nsm

issi

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(%

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14-May

19-May

20-May

Slide 2

Theoretical Transmission

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Series1

Slide 4

  Exp (nm) Theo (nm) Error (%)

Air      

Cr 6.1 5 22

Cu 144.7 150 3.533333

Cr 5.6 5 12

Glass Slide      

Slide 4

Experimental Transmission

0

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0 200 400 600 800 1000

Wavelength (nm)

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ns

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19-May

20-May

Slide 4

Theoretical Transmission

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Slide 5

  Exp (nm) Theo (nm) Error (%)

Air      

Cr 6.8 5 36

Cu 50.5 50 1

Cr 6.3 5 26

Glass Slide      

Slide 5

Experimental Transmission

0

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ns

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19-May

Slide 5

Theoretical Transmission

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Series1

Things to do:

• Get micrograph of Cr-Cu-Cr mirrors

• Schedule FTIR analysis for mirrors

• Perform adhesion tests on Cr-Cu-Cr mirrors

• Finalize anti-reflection design

• Modify evaporation set-up to allow evaporation of new film materials.

Paper Report

• Multilayer antireflection coatings for the visible and near-infrared regions– H. Ganesha Shanbhogue, C. L. Nagendra, M. N.

Annapurna, S. Ajith Kumar, and G. K. M. Thutupalli– 1 September 1997 Vol. 36, No. 25 APPLIED OPTICS

Introduction

• Current research involves improving:– optical performance over a wider spectral

range– transmission efficiency– spectral coverage– angle-of-incidence stability– durability– efficiency (residual reflection loss)

Introduction

• Problems:– AR coatings on a variety of glass substrates

• Different indices, chemical compositions, hardness, environmental stability, etc.

– Different uses• Residual reflection loss, transmission efficiency,

angle of incidence stablity, etc.

Optical material combinations

• MgF2 and medium or high index materials

• MgF2 and ZrTi04 and Zr02 (sub2)

• MgF2 and Si02, Al2O3, oxides of tantalum, titanium zirconium, and niobium

• Sub1 and Ta2O5+SiO2,TiO2+Ta2O5 and SiO2+TiO2

Optical Material Preparation and Characterization

• Sub2– E-beam evaporation– Base pressure: 10-5 mbar– Added high purity dry oxygen: 10-4 mbar

Optical Material Preparation and Characterization

• Hitachi double-beam spectrophotometer, Model U 3400

Optical Material Preparation and Characterization

Optical Material Preparation and Characterization

• MgF2

– Same fabrication set-up– Substrate temperature: 200°C– 2x10-5 mbar

Optical Material Preparation and Characterization

• Tpeak: transmission peak

• A: Cauchy dispersion constant

Optical Material Preparation and Characterization

• MgF2 index of 1.35±0.01

• Literature value of 1.38-1.37

Design optimization

• Seven layer system of MgF2 and Sub2 coatings in alternate layers– Wideband (WB) AR coatings– Limited band (LB) AR coatings

• OPTOSOFT- software to optimize design

Design optimization

Design optimization

Experimental investigation

• Leybold Hereaus vacuum evaporation plant Model 560L– Optically polished and cleaned glass

substrates– Substrate temperature: 200 ±5°

– Rate: 0.3-0.5 nm/s for MgF2 and 0.05-0.1 nm/s for Sub2

Experimental investigation

• Optical transmittance and reflectance

• Durability tests– High-temp. humidity– Thermal shock/ cycling– hot-cold soak.

Experimental investigation

Experimental investigation

Experimental investigation

Experimental investigation

Conclusions

1. IRL R*, Rav, ripple Rmax are interlinked to spectral bandwidth. The higher the bandwidth, the higher R*/Rav and the Rmax.

2.Higher-ripple designs can also have global optical properties (R*/Rav and Tav) that are comparable with those of lower-ripple designs but they have higher spectral instability.

Conclusions

3. Sub2 high-index material in combination withMgF2 allows the production of efficient AR coatings with the electron-beam evaporation technique, in terms of both optical properties and durability of the coatings.