Diffractive optics, if not yet a household word, is certainly a household
phenomenon. Many systems encountered in our everyday world contain or use
diffractive optics. A good example is DVD players or barcode scanners. Elements
that work on the principles of diffraction, or diffractive optical elements (DOEs),
can successfully replace refractive elements used in different systems. This is
because DOEs are capable of manipulating light in ways not possible by
conventional refractive optical elements. In addition, DOEs are light in weight and
compact compared to their refractive counterparts. The development of this
technology will encourage the conversion of bulky refractive optical systems into
highly compact, lightweight diffractive optical systems. It is our belief that
fabrication of diffractive optics needs to be further developed and simplified so
that more diffractive elements replace refractive elements in the future. We hope
that this book will ease this transition.
Several excellent books (see Chapter 1, Refs. 6, 33, and 57–59) already exist that explain the basics and important
concepts in the field of DOEs. This book does not intend to replace them. Rather,
the idea is to supplement the available information with a text that will equip one
with the skills required to start designing, simulating, and even fabricating
diffractive optics. Given the many different applications and uses of diffractive
optics, the importance of this field cannot be underestimated. Surprisingly, there
are only a few books that provide a hands-on approach to the field. The lacuna of
such information from a single source motivated us to create a resource based on
our practical experience. In this book, learning occurs with assistive MATLAB®
codes that enable visualization of the ideas presented and a better understanding of
the parameters controlling different aspects of light. We believe that this manner
of treatment will enable a new graduate student to quickly grasp the fundamentals
of diffractive optics, beginning with the design of simple DOEs and moving to
more complex ones.
We hope the reader will benefit from this practical approach to designing and
fabricating diffractive optical elements. Experimentalists will be able to design
appropriate structures that can be used in many different applications such as
spectroscopy, optical trapping, or beam shaping. The design of DOEs is presented with simple equations and step-by-step procedures for simulation—from the
simplest 1D grating to the more-complex multifunctional DOEs—along with
analysis of their diffraction patterns using MATLAB. The fundamentals of
fabrication techniques such as photolithography, electron beam lithography, and
focused ion beam lithography with basic instructions for the beginner are
presented. Basic error analysis and error-correction techniques for a few cases are
also discussed. It must be noted that this book will focus only on passive DOEs;
SLMs are not required for demonstration. However, the MATLAB codes provided
can be used for displaying DOE designs on SLMs as well. Thus, we hope that this
book will help not only new students but also scientists in the industry to quickly
learn techniques to help with the design, simulation, and testing of DOEs.
The book consists of eight chapters. A brief summary of the content of each
chapter is as follows:
Chapter 1 introduces the fundamentals of diffractive optics and compares
diffractive and refractive optics. A quick review of the theoretical formulation of
diffraction are presented, along with different theoretical approximations and their
validity regimes.
Chapter 2 presents the fundamentals of design and far-field analysis of simple
binary DOEs such as 1D and 2D gratings, axicons, and Fresnel zone plates (FZPs).
It shows the beginner how to make simple calculations to extract the intensity
values and spacing between the different diffraction maxima.
Chapter 3 discusses the design, simulation aspects, and far-field analysis of
multilevel and blazed DOEs such as multilevel gratings, diffractive axicons, blazed
FZPs, axilenses, spiral phase plates, etc. It also discusses the basic algorithms for
designing DOEs to obtain any desired intensity profile.
Chapter 4 describes the design and analysis of DOEs in the Fresnel diffraction
regime to simulate diffraction patterns at different planes in the propagation
direction. It also discusses some interesting phenomena such as the Talbot effect.
Chapter 5 presents the basic aberration correction techniques used to reduce
and avoid errors while designing DOEs.
Chapter 6 introduces the art of creating different advanced multifunctional
DOEs, along with their design, simulation, and analysis. The important properties
of multifunctional DOEs are also discussed.
Chapter 7 describes the design and analysis of holographic optical elements
for different applications. Computer-generated Fourier and Fresnel holography
techniques are also discussed.
Chapter 8 presents the fundamentals of designing lithography files and the
fabrication of DOEs using photolithography, electron beam lithography, and
focused ion beam lithography, with basic fabrication recipes provided.
The content of the chapters is supported throughout by clearly commented
MATLAB codes, making this book useful even to a novice programmer.
Happy Diffracting!
A. Vijayakumar and Shanti Bhattacharya
November 2016
