2012
Why This Course/Objective
Advanced optical thin films are being used increasingly in communications, optical systems, and light control and collection applications. The sophistication of the optical coating industry is advancing rapidly to meet ever increasing demands for performance and production capability. New viewpoints, equipment, and processes are available to support advanced capability and efficiency. Objectives of this course include: to provide increased knowledge and understanding of the many practical aspects of optical coating design and production, to give hands-on design experience in the techniques and principles discussed, and to elucidate techniques and processes that are commonly successful in meeting optical coating needs.
Benefits for You
This course will enable you to:
*firmly grasp, visualize, and use design principles and graphical methods in thin film design
*gain hands on computer aided design experience in applying the concepts of this course
*understand Fourier thin film synthesis and compare rugate and discrete layer designs
*estimate what can be achieved before starting a design
*solve practical coating design problems in class
*select appropriate optical coating equipment to support the needed processes
*be familiar with the properties and process know-how for common optical coating materials
*learn about DOE process development techniques and the use of various ion/plasma sources
*understand various monitoring and control strategies and their advantages and limitations
Valuable Take-home Materials
Mr. Willey's books the Practical Design of Optical Thin Films and Practical Production of Optical Thin Films and software for special calculations and graphics will be provided along with supplementary class notes, and the free version of the internationally used FilmStar design and evaluation software by Fred Goldstein. These can be valuable for future reference.
Who Should Attend, Who Will Benefit
The course is intended to be valuable to new coating engineers, scientists, technical managers, and technicians as well as seasoned thin film scientists who are involved in design, development, and production of optical thin films. Basic principles are laid out from the beginning for those new to the field, but the evolution of the topics then moves into material and techniques useful to even the more experienced practitioners. No extensive background in mathematics or physics is required; extensive graphical illustrations are used.
Course Instructor
Ron Willey is a consultant with over 40 years in the fields of thin film and optical system design, development, and production. He is a graduate of MIT in optical instrumentation and has an MS in computer science from FIT. He has lead groups in optical coating and instrumentation development and production at Martin Marietta, Raytheon, Opto_Mechanik, and LexaLite International. He is very experienced in practical thin films design, process development, and the application of industrial Design Of Experiment methodology (DOE). He holds four patents and has published many papers on optical coating, optical design, and economics of optical tolerances. He is a Fellow of the SPIE and the Optical Society of America.
Course Outline
(Taken directly from the Table of Contents of the Two
Books used in the Course.)
MONDAY
Fundamentals of Thin Film Optics 1
1.1. INTRODUCTION 1
1.2. REVIEW OF THIN FILM OPTICS PRINCIPLES 5
1.3. REFLECTANCE DIAGRAMS AND DESIGN 12
1.3.1. Low Reflectors, Antireflection Coatings 15
1.3.2. Physical Thickness versus Optical Thickness 22
1.3.3. Three-Layer AR Coating on Germanium, Example 22
1.3.4. Example Four-Layer Broad Band AR Coating in the Visible 26
1.3.5. Behavior of a High Index Slab 27
1.3.6. High Reflectors 29
1.3.7. Beamsplitters 36
1.3.8. Higher Harmonic Reflection Bands 36
1.3.9. Minus Filters and Narrow Blocking Bands 39
1.3.10. Another Approach to Narrow Blocking Bands 41
1.3.11. Fencepost and Posthole Design Approaches 42
1.4. APPROXIMATIONS OF INDICES AND DESIGNS 46
1.4.1. Herpin/Epstein Periods 46
1.4.2. More General Approximations 48
1.5. INHOMOGENEOUS INDEX FUNCTIONS 51
1.5.1. Step-Down Functions 52
1.5.2. Low Index Limitations 59
1.5.3. Lithographic “Moth-Eye” ARs 61
1.5.4. Overcoming Low Index Limitations With Thickness 63
1.5.5. Additional Thickness Functions 63
1.5.6. A Fourier Approach 69
1.5.7. Rugates and the EUV/Soft X-ray Spectral Region 74
1.5.8. Potential Quantization Effects in Designs for EUV Mirrors 86
1.6 ANGLES AND POLARIZATION 92
1.6.1. Wavelength Shift with Angle of Incidence 92
1.6.2. Polarization Effects of Angle of Incidence 93
1.6.3. Polarization as Seen in Reflectance Amplitude Diagrams 96
1.6.4. Polarizing Beamsplitters 99
1.6.5. Non-Polarizing Beamsplitters 102
1.7. ADDITIONAL VIEWS VIA GRAPHICS AND PLOTS 106
1.7.1. Admittance Diagrams 106
1.7.2. Ellipsometry Plots 109
1.7.3. Additional Graphics for Visualization 117
1.8. TRIANGLE DIAGRAMS AND DESIGN 118
1.8.1. Designing Coatings with Absorbing Materials 121
1.8.2. Induced Transmission Filter Example 131
1.8.3. NBP Reflection Filter Example 134
1.8.4. AR Coated Variable Neutral Density Filter Example 137
1.8.5. Conclusions of Designing With Metals 142
1.9. NARROW BANDPASS FILTERS 142
1.9.1. NBP Wavelength Effects as Seen on Reflectance Diagrams 149
1.9.2. Dense Wavelength Division Multiplexing (DWDM) Filters 152
1.9.3. Fiber Bragg Gratings 155
1.10. FENCEPOST DESIGN EXAMPLES 155
1.10.1. Edge Filters 158
1.10.2. Fencepost Narrow Bandpass Filters 160
1.11. OPTIMIZATION 163
1.11.1. Performance Goals and Weightings 164
1.11.2. Global versus Local Minima 165
1.11.3. Some Optimizing Concepts 166
1.11.4. Constraints 171
1.11.5. Quantization 173
1.12. SUMMARY 175
1.13. REFERENCES 176
TUESDAY
Estimating What Can Be Done Before Designing 181
2.1. INTRODUCTION 181
2.2. ANTIREFLECTION COATINGS 181
2.2.1. Procedure 182
2.2.2. The Formula 183
2.2.3. Results 185
2.2.4. Berlin AR Design Contest 189
2.2.5. Results of Further Study 191
2.2.6. Estimating the Number of Layers 197
2.2.7. Looking Outside the Box 199
2.2.8. Reverse Engineering Using Number of Ripples in Band 203
2.3. BANDPASS AND BLOCKER COATINGS 204
2.3.1. Estimating the Width of a Blocking Band 204
2.3.2. Estimating the Optical Density of a Blocking Band 206
2.3.3. Estimating the Number of Layers and Thickness Needed 207
2.3.4. Estimating More Complex Coatings 208
2.3.5. Estimating Edge Filter Passband Reflection Losses 214
2.4. DICHROIC REFLECTION COATINGS 223
2.5. DWDM FILTERS 225
2.6. ESTIMATING OD AND BW OF FENCEPOSTS 230
2.7. SUMMARY 233
Fourier Viewpoint of Optical Coatings 237
3.1. INTRODUCTION 237
3.2. FOURIER CONCEPTS 237
3.2.1. Background 239
3.2.2. Some Limitations 247
3.2.3. A Method to Determine the Multiple Reflections 253
3.3. SUMMARY 255
3.4. REFERENCES 256
AR Coating Design Example 279
C.1. DESIGNING A VBBAR 279
C.2. OTHER EXAMPLES 291
C.3. REFERENCES 294
Color Measurement, Introduction 297
D.1. WHAT IS COLOR MEASUREMENT? 297
D.2. REFERENCES 303
WEDNESDAY
Typical Equipment for Optical Coating Production 1
1.1. INTRODUCTION 1
1.2. GENERAL REQUIREMENTS 2
1.2.1. The Vacuum 4
1.2.2. Deposition Sources 20
1.2.3. Fixturing and Uniformity 48
1.2.4. Temperature Control 58
1.2.5. Process Control 62
1.3. TYPICAL EQUIPMENT 64
1.4. ALTERNATIVE APPROACHES 68
1.5. UTILITIES 68
1.6. REFERENCES 73
Materials and Processes 81
2.1. INTRODUCTION 81
X.X. SPECTROPHOTOMETERS
X.X.X Monochrometers
X.X.X Double-Beam Photometers
X.X.X Fourier Spectrometers
X.X.X Diffuse Reflectance and Integrating Spheres
X.X.X Measuring Transmittance and Error Sources
X.X.X Calibrating and Measuring Specular Reflectance
X.X.X Angular and Absolute Reflectance
X.X.X An Alternative Optical Coating Spectrometer
Y.Y. COLOR MEASUREMENTS
Y.Y.Y. Some Color Software Tools
Z.Z. Finding n and k Values
2.1.0. Measuring Spectral Results in the Real World 81
2.1.1. Index of Refraction Determination 91
2.2. PROCESS KNOW-HOW 101
2.2.1. Film Growth Models and Observations 102
2.2.2. Chiral and Sculptured Coatings 107
2.2.3. Stress in Coatings 107
2.2.4. Laser Damage in Coatings 109
2.2.5. Rain Erosion of Coatings 112
2.3. MATERIALS 114
2.3.1. Some Specific Materials 115
A.A.A. Setting Crystal Controller PID Values
2.4. ION SOURCES 160
2.4.1. Cold Cathode Source 161
2.4.2. End-Hall Source 163
2.4.3. PS1500 Plasma/Ion Source 166
2.5. ION/ATOM RATIOS AND IMPLICATIONS 179
2.6. OTHER PROCESSES TO CONSIDER 183
2.6.1. Physical Vapor Deposition 184
2.6.2. Dip, Spin, and Spray Coatings 185
2.6.3. Chemical Vapor Deposition 185
2.6.4. Plasma-Enhanced CVD 186
2.6.5. Plasma Polymerization 186
2.6.6. Hard Carbon Coatings 187
2.7. SUMMARY 189
2.8. REFERENCES 190
THURSDAY
Thin Film Monitoring and Control 249
4.1 Effects of Errors 252
4.2 Ways to Monitor 256
4.2.1. "Eyeball" and Measured Charge 258
4.2.2. Time-Power/Rate Monitoring 261
4.2.3. Crystal Monitoring 261
4.2.4. Optical Thickness Monitors 264
4.2.5. Trade-offs in Monitoring 278
4.3 Error Compensation and Degree of Control 279
4.3.1. Narrow Bandpass Filter Monitoring 280
4.3.2. DWDM Filter Monitoring 285
4.3.3 Error Compensation in Edge Filters 308
4.3.4. Broad Band Monitoring Compensation 309
4.3.5. Effects of Thin Film Wedge on the Monitor Chip 310
4.3.6. Error Due to Width of the Monitoring Passband 312
4.4 Calibrations and Variations 314
4.4.1. Tooling Factors 315
4.4.2. Variations 316
4.4.3. The Optical Monitor with Crystal Method of Schroedter 317
4.4.4. Suggestion for Computer Aided Monitoring of DWDM Filters 319
4.5 Sensitivity and Strategies 320
4.5.1. Sensitivity versus Layer Termination Point in Reflectance 320
4.5.2. Sensitivity Versus g-Value 322
4.5.3. Precoated Monitor Chips 325
4.5.4. Eliminating the Precoated Chip 326
4.5.5. Constant Level Monitoring Strategies 333
4.5.6. Steering the Monitoring Signal Result 338
4.5.7. Variation of Band-Edge Position with Monitoring Errors 346
4.5.8. Almost Achromatic Absentee Layers 355
4.6 Practical Considerations 358
4.6.1. A Narrow Bandpass Filter 358
4.6.2. A Special "Multichroic" Beamsplitter 359
4.6.3. A Very Broadband Antireflection Coating 361
4.6.4. Intermittent Monitoring 367
4.6.5 Single Beam versus Double Beam Optical Monitors 368
4.6.6. Automation versus Manual Monitoring 369
4.7 Fencepost Monitoring 371
4.8 Monitoring Non-QWOT NBP Filters 376
4.9 Summary 389
4.10 References 391
Banquet (Included in Course Fee)
FRIDAY
Process Development 219
3.1. INTRODUCTION 219
3.2. DESIGN OF EXPERIMENTS METHODOLOGY 223
3.2.1. Process Flow Diagram 223
3.2.2. Cause-and-Effect Diagram 224
3.2.3. Control, Noise, or Experiment 224
3.2.4. Standard Operating Procedures 226
3.3. DESIGN OF THE EXPERIMENTS: EXAMPLES 226
3.3.1. A Central Composite Design for Aluminizing 227
3.3.2. A Box-Behnken Design for IAD Deposition of TiO2 231
3.4. A REAL LIFE EXAMPLE OF PROBLEM SOLVING 238
3.5. SUMMARY 248
3.6. REFERENCES 248
Note: The order of presentations may be changed without notice.
(Updated 8-12-11)