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Spie Press Book

Field Guide to Digital Micro-Optics
Author(s): Bernard C. Kress
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Book Description

Digital micro-optics is a particular field within the more general field of optical engineering, particular in the way such optics are designed (seldom through ray tracing) and how they are fabricated (often at the wafer scale). This book, written by Google engineer Bernard Kress, reviews the broad range of micro-optics used today in industry and research (refractives, GRIN, hybrid, diffractives, holographic, nano-optics). It provides quick access to optimal design and modeling techniques, both analytic and numeric. This book also reviews the various fabrication techniques used to produce micro-optics, as well as the requirements to bridge the gap between design and fabrication. The optical engineer interested in quick but concise answers to questions ranging from the design and modeling to the fabrication and mass replication of micro-optics will particularly enjoy this book.

Book Details

Date Published: 15 October 2014
Pages: 180
ISBN: 9781628411836
Volume: FG33

Table of Contents
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Glossary of Symbols and Acronyms

Refractive Micro-Optics
Digital Micro-Optics
Naming Conventions
Free-Space and Guided-Wave Micro-Optics
Maximizing the Refractive Effect
Maximizing the Diffractive Effect
Total Internal Reflection
Guided-Wave Digital Optics
Optical Waveguide Types
Modes in Optical Waveguides
Coupling Losses in Optical Waveguides
Free-Space Micro-Optics
Refractive Micro-Optics
Graded-Index Micro-Optics
GRIN Lenses
Spectral Dispersion in Micro-Optics
Imaging with Microlens Arrays
Light-Field Cameras
Light-Field Displays
Beam Steering with MLAs
Beam Shaping/Homogenizing with MLAs
Diffractive Micro-Optics
Digital Diffractive Optics
Analytic and Numeric Diffractives
Fresnel and Fourier Diffraction Regimes
Fourier and Fresnel Diffractive Optics
Analytic Diffractive Elements
Reflective Gratings
Amplitude Gratings
Binary Phase Gratings
Multilevel Diffractives
Diffractive Lens Surface Profiles
Diffraction Efficiency
Diffractive Fresnel Lens
Diffractive Lens Profile Descriptions
Microlens Parameters
Spectral Bandwidth of Diffractives
Broadband Diffractives
Achromatizing Hybrid Lenses
Athermalizing Hybrid Lenses
Hybrid Lens Surface Descriptions
Hybrid Refractive/Diffractive Lens
Aberrations in Micro-Optics
Beam-Shaping Lenses
Vortex Microlenses
Extended Depth of Focus Microlenses
Aperture and Wavefront Coding
Spatially Multiplexed Planar Optics
Diffractive Null Lenses
Interferogram Lenses
Toroidal and Helicoidal Planar Lenses
Iterative Optimization Process
Numerical Optimization
Numeric Diffractives
CGH Design Constraints
Merit Function Definition
IFTA Algorithm
Direct Binary Search
Simulated Annealing
Beam-Shaping CGHs (Numeric)
Spot Array Generators
MLAs and Multifocus Lenses
Dammann Gratings
Talbot Self-Imaging
From Micro-Optics to Nano-Optics
Subwavelength Optics
Large- and Small-Period Gratings
Zero-Order Gratings
Rigorous EM Diffraction Theory
Effective Medium Theory (EMT)
EMT Encoding Schemes
Form Birefringence
Antireflection Microstructures
Parity-Time Symmetry in Optics
PT Grating-Assisted Couplers
Nonreciprocal Free-Space PT Gratings
Surface Plasmonics
Photonic Crystals
Metasurfaces and Resonant Antennas
Holographic Micro-Optics
The Holographic Process
Gabor and Leith Holograms
Thin and Thick Holograms
Reflection and Transmission Holograms
Fraunhofer and Fresnel Holograms
Holographic Interference
The Grating Vector
Floquet's Theorem and the Bragg Conditions
Grating Strength and Detuning Factor
Kogelnik Theory for Volume Holograms
Angular and Spectral Bandwidths in Holograms
Two-Step Holographic Recording
Surface-Relief Holograms
Holographic Recording Media
Dynamic Micro-Optics
Dynamic Micro-Optics
Liquid-Crystal Optics
Liquid-Crystal Microdisplays
OLED Microdisplays
Quantum-Dot Displays
H-PDLC Switchable Hologram
H-PDLC Recording and Playback
MEMS/MOEMS Micro-Optics
MEMS Gratings
MEMS Display Panels
MEMS Laser Scanners
Holographic Backlights and Displays
Tunable Moire Micro-Optics
Liquid Micro-Optics
Electroactive Polymer Microlenses
Micro-Optics Modeling Techniques
Diffraction Modeling Theories
Ray Tracing through Diffractives
Fresnel and Fourier Approximations
Near- and Far-Field Regions
FFT-Based Physical Optics Propagators
Oversampling Process in CGH Modeling
Physical Optics Modeling: Resolution Increase
Physical Optics Modeling with FFT Algorithms
Replication of CGHs
Numerical-Reconstruction Windows
Numerical-Reconstruction Window Scaling
DFT-Based Propagators
Fresnel Propagator Using a DFT
Arbitrary-Reconstruction Windows
DFT-Based Numerical Propagator
Physical Optics versus Ray Tracing
Micro-Optics Fabrication
Fabrication of Micro-Optics
Holographic Exposure and Etching
Multiple Holographic Exposures
Refractive Micro-Optics Fabrication
Sag Calculations for Microlenses
Diamond Ruling/Turning
Binary Lithography
Multilevel Optical Lithography
Etch-Depth Calculations
Multilevel Lithographic Fabrication
GDSII Mask Layouts
Wafers for Micro-Optics
Optical Lithography
Step-and-Repeat Lithography
Useful Lithography Parameters
Direct-Write Lithography
Greyscale Masking Techniques
Greyscale Lithography (Binary)
Greyscale Lithography (HEBS)
Photomask Patterning
Optical Proximity Correction
Replication Shim
Shim Recombination
Plastic Replication Technologies
Roll-to-Roll UV Embossing
Plastics Used in Injection Molding
Effects of Fabrication Errors
Micro-Optics in Industry
Application Realm of Micro-Optics


The term "digital micro-optics" was introduced in the early 1990s to refer to a specific variety of micro-optics. It is now widely accepted by industry and academia. Digital micro-optics can be related to their counterparts in the electronics realm - "digital electronics," or "integrated electronics" (ICs) - in various ways, from design to modeling, from prototyping to mass fabrication, and eventually system integration. Historically, the term "digital" in digital electronics refers to three aspects:

  • their digital functionality (binary logic),
  • the way they are designed via a digital computer, and
  • the way they are fabricated (through sets of digital or binary masks).

In digital micro-optics, the term primarily refers to how such optics are designed and fabricated, similar to digital electronics, through specific electronic-design-automation (EDA) software packages and sets of digital masks. Traditional macro-optics, such as telescopes, microscopes, and other imaging optics, have been designed without complex design software tools. Digital optics, especially wafer-scale micro-optics, cannot be designed without specific software and tools. Digital layouts for wafer-level fabrication of micro-optics are also often generated by algorithms similar to the ones used in conventional EDA tools (Cadence, Synopsys, Mentor-Graphics, etc.). Because there is often no analytical solution to the micro-optics design problem, complex iterative optimization algorithms may be required to find an adequate solution.

Unlike digital electronics, digital micro-optics can implement either digital or analog functionality, or a combination thereof. A typical digital function may be a fan-out beam splitter, and an analog function may be an imaging task. A hybrid may result in a complex multi-focus imaging lens, a function impossible to implement in traditional analog macro-optics.

Bernard C. Kress
Google [X] Labs, Mountain View, CA

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