IEEE TRANSACTIONS ON EDUCATION, VOL. E-23, NO. 2, MAY 1980

M. .T.'s Modern Optics Project Laboratory

CARDINAL WARDE, MEMBER, IEEE

Abstract-This paper describes the Modern Optics Project Laboratorycourse offered within the Department of Electrical Engineering andComputer Science at the Massachusetts Institute of Technology (M.I.T.)With a combination of lectures, laboratory exercises, and projects, thiscourse provides the students with a broad exposure to the principles ofmodern optics and quantum electronics, and gives them an opportunityto develop basic experimental skills in optics.

INTRODUCTIONPROJECT-TYPE laboratories were introduced at M.I.T.

about 16 years ago because the existing laboratory courseswere said to be "dull and cookbookish," thereby discouragingrather than stimulating the students. The one-semester ModernOptics Project Laboratory was first offered in the fall of 1967in what was then the Department of Electrical Engineering.'Since that time, the course has undergone several revisions instructure, scope, and content. Its goal is to provide the stu-dents with the opportunity to develop basic experimental skillsin modern optics and quantum electronics by teaching themhow to plan experiments, formulate hypotheses, solve prob-lems associated with instrumentation and data processing, ob-serve the phenomena being investigated, and report the findingsin a professional manner. This is accomplished through aseries of lectures, laboratory exercises, and projects.Most of the students taking this course are juniors or seniors,

and this is generally their first exposure to an optics laboratory.They have had one semester of linear systems theory and onesemester of electrostatics, and are either taking or have takena follow-on course in electrodynamics; thus, at the very least,the typical student is familiar with the one-dimensional Fouriertransform, Maxwell's equations, and the wave equation.The students carry out their laboratory exercises in the Mod-

ern Optics Laboratory, which now occupies about 750 squarefeet of space on a floor dedicated to the department's under-graduate laboratories. The laboratory is furnished with threeoptical tables, one of which is sufficiently vibration-isolated tobe adequate for holography and interferometry. In addition,the laboratory is equipped withSeveral multimode 2 mW, 6328-A, He-Ne lasers;One single-mode TEMo0, 5 mW, 6328-A, He-Ne laser;One homemade CW, 10.6 ,um, CO2 laser;

Manuscript received December 28, 1979, revised January 28, 1980.The author is with the Department of Electrical Engineering and Com-

puter Science, and the Center for Materials Science and Engineering,Massachusetts Institute of Technology, Cambridge, MA 02139.

' The words "and Computer Science" were added in January of 1975.During the period from 1967 to 1975, several faculty members wereinvolved with the Laboratory: these include Profs. T. Bridges, H. A. Haus,P. Hoff, E. Hoversten, T. S. Huang, R. S. Kennedy, and J. H. Shapiro.The author has been in charge of the Laboratory since September 1975.

One homemade flashlamp-pumped dye laser;Two pulsed infrared semiconductor diode lasers;One scanning Fabry-Perot spectrometer;One homemade Fabry-Perot interferometer;Two electrooptic modulators (1 commercial ADP and 1

homemade LiNbO3 modulator);One 2 m scanning grating spectrometer (Jarrell-Ash);One infrared prism spectrometer (Perkin-Elmer);One lock-in amplifier;One 10 kG water-cooled electromagnet;Two 1 km spools of multimode graded-index optical fiber;Several photomultiplier tubes and silicon photodiodes;An adequate number of standard optical elements and instru-

mentation, such as lenses, filters, polarizers, photographic andholographic film, power supplies, amplifiers, and oscilloscopes.

STRUCTURE

For the first six weeks of the semester there are two lecturesand one group of complementary laboratory exercises eachweek. These initial lectures focus on the fundamentals of op-tical phenomena, devices, systems, and techniques, and thecomplementary laboratory exercises provide direct observationor measurement of the phenomena discussed in the lectures.Each group of laboratory exercises remains assembled for atwo-week period. This provides the scheduling flexibilitynecessary to accommodate those students who may occa-sionally be absent for some legitimate reason.The combination of lectures and complementary laboratory

exercises is designed to rapidly increase the students' compe-tence in handling optical systems (including safety aspects)and to provide, as quickly as possible, a sufficiently broadexperimental and theoretical background to enable them tostart the projects that they undertake in the second half ofthe course.For the remaining seven weeks of the semester, the students

engage in projects in the areas of modern optics and quantumelectronics. The projects are conducted in the Modern OpticsLaboratory and in the laboratories of faculty and staff mem-bers engaged in research in these areas. These faculty and staffmembers serve as supervisors of the projects. During this pe-riod, the focus of the lectures shifts from a development ofthe fundamentals to a survey of contemporary and specializedtopics in modern optics and quantum electronics.To encourage outside reading, one homework problem is

assigned each week for the entire semester. A set of notescovering the material in the lectures and describing the six setsof laboratory exercises is made available to the students at thebeginning of the semester. Each lecture is supplemented with

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a recommended reading assignment from at least one of severaltextbooks [11-[7].

INITIAL LECTURES AND LABORATORY EXERCISES

The lectures begin with a review of Maxwell's equations andthe derived wave equation. Particular attention is paid to thepolarization states of the electromagnetic field, Brewster'sangle, and the Fresnel equations. The complementary groupof laboratory exercises consist of four experiments.

1) The student learns how to find the axes of a sheet oflinear polarizer, and then measures and plots the curves for ex-ternal reflection from a glass block as a function of the angleof incidence for light polarized parallel and perpendicular tothe plane of incidence.2) The student simulates the various states of polarization

of the electromagnetic field. This is done by admixing twosinusoidal voltage signals (of the same frequency) and adjustingtheir phases and amplitude to form Lissajous figures on anoscilloscope.3) The student is assigned the task of finding the fast and

slow axes of a quarter-wave plate.4) The student is given a flexible sheet of "magic material"

that transmits light when folded in one direction about a givenaxis and blocks light when folded in the opposite directionabout the same axis. The student is asked to design and carryout simple polarization experiments to determine the op-tical elements that constitute the "magic material," and therelative orientation, if any, that exists between the elements.The magic material is a sheet of circular polarizer.The next topic covered is interference. The lectures comprise

a qualitative discussion of spatial and temporal coherence,methods of creating mutually coherent beams, and two-beamand multiple-beam interferometers. In the discussion of multi-ple beam interference produced by a thin, plane-parallel, di-electric medium, the Airy formulas are derived; the dependenceof the transmitted and reflected intensity patterns on angle ofincidence, thickness, refractive index, and finesse are discussedin detail. The complementary group of laboratory exercisesconsists of five experiments.

1) The setting up and alignment of a Mach-Zehnder inter-ferometer, with 5-cm optics, and the use of it to measure theparallelism of microscope slides.2) The setting up and operation of a homemade laser Michel-

son interferometric velocimeter.3) Analysis of the fringe pattern produced by the homemade

Fabry-Perot interferometer with 6328-A light.4) Analysis of the multiple beam interference pattern from

a thin (-150,m thick) Lummer-Gehrcke plate (made from acover glass slide and a small prism) [8] illuminated with 6328-A laser radiation.

5) Qualitative analysis of the Haidinger fringes from a thincover glass slide in collimated laser light. The student is askedto observe and explain the changes in, and the relationshipbetween, the reflected and transmitted fringe pattems as theangle of incidence is varied.The rudiments of scalar diffraction theory are covered next.

The Fresnel diffraction formula is derived via the Green'sfunction approach, and the necessary approximations aremade to derive the Fraunhofer diffraction formula. The con-cept of spatial frequency is introduced, and the relationshipbetween the Fraunhofer diffraction pattern and the Fouriertransform of the aperture transmittance function is established.The Fraunhofer patterns from simple apertures (for example,single slit, rectangular aperture, circular aperture) are thencalculated. Finally, the Fresnel zone approach is presentedas a technique of limited usefulness that can be of some helpin understanding the qualitative features of the near-fielddiffraction pattern from apertures with circular symmetry.The group of laboratory exercises on diffraction involves theanalysis and interpretation of the Fraunhofer and Fresneldiffraction patterns from slits, diffraction gratings, rectangularand triangular apertures, rectangular grids, and small circularopenings and obstacles.The principles of Fourier optics follow naturally, especially

now that a relationship has been established between theFraunhofer diffraction pattern and the Fourier transform ofthe aperture. In the lectures on Fourier optics, the phasetransformation for a thin lens is derived from first principles,and the Fourier transforming property of the thin lens is de-veloped. Spatial ffltering and simple optical processing systemsthat perform the operations of convolution, correlation, andmatched flUtering, for example, are discussed next. In thecomplementary group of laboratory exercises, the experimentsinvolve

1) setting up a simple optical processor for spatial filteringexperiments; and2) using the optical processor to observe the Fourier trans-

forms of a number of objects (for example, a rectangular grid,a collection of random apertures) and to demonstrate spatialfiltering; included in the spatial flltering demonstrations arethe Abbe-Porter experiments on the rectangular grid and theSchleiren phase contrast technique.Attention then shifts to the modulation of optical radiation.

Because of time constraints, the emphasis is primarily onelectrooptic modulation (acoustooptic modulation is discussedbriefly and the student is encouraged to consult the supple-mentary reading assignment from [2] for the details). Thelectures on electrooptic modulation provide a brief descriptionof wave propagation in anisotropic materials; the electroopticeffect and the electrooptic tensor are discussed, and the phaseretardation for the linear longitudinal effect in a 42m crystalis calculated. The intensity transmission as a function ofappliedvoltage for a longitudinal modulator is developed in the class-room, and the analogous derivation for a transverse modulatoris assigned as a homework problem. In the associated labora-tory exercise, the following experiments are carried out:

1) The student sets up a homemade transverse LiNbO3 mod-ulator (the product of a project carried out a few years earlier)between crossed polarizers, and measures and plots the trans-mitted intensity for 6328-A laser light as a function of applieddc voltage. The student is asked to identify the halfwavevoltage and compare the experimental with the calculatedcurve.

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WARDE: MODERN OPTICS PROJECT LAB

2) The student then electrically biases the modulator at anoperating point near the most linear region of its transmissioncurve, measures the frequency response of the system withsinusoidal voltage inputs, and explains the results.3) The student assembles a short-range atmospheric optical

communication system, in the laboratory (similar to that de-scribed on p. 259 of [2], and compares its performance withthat of a flber optic system that he or she assembles using thesame modulator and a few meters of multimode fiber.

Three lectures highlighting the interaction of optical radia-tion with matter and culminating with the principle of the laserare presented next. The lectures cover the distinction betweenspontaneous and stimulated transitions, between homogeneousand inhomogeneous broadening, and discuss the use of absorp-tion and fluorescence spectroscopy as tools for studying atomicstructure. Pumping, the rate equations for a three-level system,population inversion, resonant frequencies, gain saturation,and other laser phenomena are also discussed. Finally, thescanning Fabry-Perot spectrometer is examined as a high-resolution spectrum analyzer for studying the wavelengthdetail of laser radiation. The laboratory exercise associatedwith this material consists of the following two parts.

1) First is an experiment in absorption spectroscopy inwhich the student uses a 2 -m Jarrell-Ash grating spectrom-eter to record the absorption spectrum of a rare-earth ion insolution. The student learns (a) how to optimally couple lightin and out of a spectrometer, (b) how to perform wavelengthcalibration of a spectrometer, (c) how to use a lock-in ampli-fier, and (d) how, in principle, the dielectric constant can bededuced from the data.2) The second part involves using a scanning Fabry-Perot

spectrometer to study the longitudinal modes of one of thelaboratory's multimode He-Ne lasers.

LECTURES ON CONTEMPORY TOPICSAfter the formal laboratory exercises are completed, the

students spend all their assigned laboratory periods workingon their projects. As mentioned previously, the lecturesthen shift from the fundamental material to contemporaryand specialized topics in modern optics and quantum elec-tronics; occasionally, other faculty members are invited to givesome of these lectures.Holography is generally the first topic. The lectures on holog-

raphy include a discussion of photographic film, its linearity,spatial resolution, and sensitivity. Also included are discus-sions of the Gabor hologram, the Leith-Upatnieks hologram,effects of film emulsion thickness, and the principles of white-light reflection holography. A few of the scientific applica-tions of holography are discussed. Because the students alwaysappear to be fascinated by holograms, an optional laboratoryexercise is offered that provides them with the opportunity to"play with" commercially made holograms and to make andanalyze their own transmission or reflection holograms.The other contemporary lecture topics include specific laser

systems, Gaussian beams and resonators, principles and charac-terization of optical detectors, fiber optics, optical communi-cation systems, and nonlinear optics.

PROJECTSAt the beginning of the semester, faculty and staff members

engaged in research in modern optics and quantum electronicsare asked to contribute written descriptions of projects theycan support and supervise. Each project is designed to be com-pleted in a period of six weeks, assuming the student spendsthe assigned eight hours per week on the project. The projectsare grouped by field, and a complete listing is distributed tothe students during the third week ofthe semester. Frequently,faculty members contribute projects that may be expandedinto bachelor's theses, and those are so labeled. The studentsselect the projects on a first-come-first-served basis. Seniorswho have not yet selected theses are encouraged to choosethose projects that may be expanded into theses. Should asenior accept this option, a specific portion of the task is carvedout to satisfy the requirements ofthe project laboratory. Uponcompletion of the work for the project, the student continuesresearch on the same or a related problem for the bachelor'sthesis. In this way, the project laboratory serves as a vehiclefor seniors who are in search of a thesis.In those cases where the students generate ideas that they

would like to pursue as projects, they are required to submitproject proposals that describe the ideas. If a proposed projectsatisfies the standards of the subject, if the required apparatus isavailable, and if a supervisor can be found, the student is al-lowed to carry out the project.After choosing a project, the student is expected to 1) im-

mediately start planning the experiment, 2) formulate anyneeded hypotheses to explain the expected results, 3) solveany problems that may arise with the instrumentation or thedata processing, 4) devise a satisfactory means of observingand recording the phenomenon being investigated, and 5)write a report of the findings in a format consistent with oneof the leading journals in optics.The projects are carried out in the Modern Optics Labora-

tory and in the laboratories of the faculty and staff memberswho contributed the projects.Examples of successfully completed projects include:Construction of an argon ion laser;Construction of a flashlamp-pumped dye laser;Construction of a CO2 laser;Construction of fiber-optic communication systems with

both LED and diode lasers as sources;Vibration analysis using multiple exposure holography;Fabrication of electrooptic modulators;Construction of matched spatial filters for a character recog-

nition system;Construction of a middle ultraviolet atmospheric communi-

cations system using a germicidal lamp as the source and a 2 ftaluminum dish to collect the light at the receiver;Forced mode locking of a pulsed CO2 laser.

REFERENCES

[li J. W. Goodman, Fourier Optics. New York: McGraw-Hill, 1968.[21 A.Yariv,IntroductiontoOpticalElectronics,2ndEd. NewYork:

Holt, Rinehart and Winston, Inc., 1976.[31 G. R. Fowles, Introduction to Modern Optics, 2nd Ed. New

York: Holt, Rinehart and Winston, 1975.

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E. Hecht and Z. Zajac, Optics. Reading, MA: Addison-Wesley,1974.M. Bom and E. Wolf, Principles ofOptics, 5th Ed. London:Pergamon, 1975.F. A. Jenkins and H. E. White, Fundamentals ofOptics, 4th ed.New York: McGraw-Hill, 1976.J. M. Ziman, Principles of the Theory ofSolids. London: Cam-bridge University Press, 1964.C. Warde, "Lummer-Gehrcke interferometer modified for thespectroscopy of thin dielectric films,"AppL Opt., vol. 15, p. 2730-2735, 1976.

Cardinal Warde (M'76) was bom in Barbados, West Indies. He receivedthe B.Sc. degree in physics in 1969 from the Stevens Institute of Tech-nology, Hoboken, NJ, and the M.PhiL and Ph.D. degrees in physics in1971 and 1974, respectively, from Yale University, New Haven, CT.

Since 1974 he has been an Assistant Professorin the Department of Electrical Engineering andComputer Science, Massachusetts Institute ofTechnology, Cambridge. His primary teachingresponsibilities have been in the areas of net-work theory, hnear systems theory, opticalelectronics, and the development of the ModemOptics Project Laboratory; he has been incharge of the Modern Optics Project Labora-tory for the past five years. His major researchactivities include the development of optically-

addressed and electron-beam-addressed spatial lght modulators for usein optical information storage and processing, as well as for high-resolution adaptive optical applications. He is also engaged in experi-mental and theoretical studies of the influence of electron beams on theoptical properties of materials. To date, he has published fifteen papersin these areas, and has presented his work at several conferences both inthe U.S. and abroad. He is currently on a year's leave of absence at theM LT. Lincoln Laboratory. Prior to this appointment, he had servedas a consultant to Lincoln Laboratory.

A Profile: The Teaching of Optics by the Facultyof The Institute of Optics

NICHOLAS GEORGE, SENIOR MEMBER, IEEE, AND KARIN STRAND

Abstract-The Institute of Optics is committed to training leaders inthe field. To do so, it draws on the excellent resources of its facultyand facilities, and emphasizes the inportaace of a broad education inoptics for students all lvels. The underpaduate and gaduate pro-

gamms are based upon a seines of required care courses that examine indepth the fundanentals of optical science and engneeing

OPTICs TODAYTHE past twenty years have been a time of unremittingTchange and renaissance in the field of optics. With the in-

vention of the laser, the hologram, and the optical fiber, opticshas emerged on the scientific scene as both an important branchof physics and an exciting field of engineering. Over the lastfifty years, The Institute of Optics has maintained its positionas one of the educational leaders in the field. Since severalarticles have chronicled its history [I] - [3], the purpose ofthis one is to focus instead on the current educational pro-

grams of The Institute of Optics.

Manuscript received January 18, 1980; revised January 29, 1980.The authors are with The Institute of Optics, University of Rochester,

Rochester, NY 14627.

Today especially, optics is a science that greatly enrichesother areas of science and technology. In physics, chemistry,and biology laboratories, for example, optical techniques are

used to measure lengths, to illuminate samples, to form images,and to detect emitted radiation. Optical data acquisition isalso a key aspect of many space programs, ranging from thedetection of environmental pollutants to the discovery of thecharacteristics of the Martian landscape. In addition, lasersare now used in everyday life, in applications such as layingdrain pipe, providing automatic scanners for supermarketcheckout systems, and automating industrial quality control.As the telephone industry switches from conventional copper

cable to fiber optics, it will require the services of many more

engineering scientists trained in optics. Advanced optical tech-nology now includes lasers, fast electrooptic and acoustoopticmodulators, low-loss fibers, wideband detectors, integratedcircuits, and holographic recording.So optics is a field with far-ranging appeal. Whether students

aspire to become theoreticians, experimentalists, engineeringscientists, or design engineers, the field of optics is broadenough to provide a challenging career and a rewarding profes-

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