Optical Physics:LABORATORY 
PHYS 307 
Optical Physics:LABORATORY 
Center for Natural Science: We have a windowless room We have a windowless room Let there be LIGHT! 
Gabe Spalding
Office Hours: CNS, room C006B 5563004 gspaldin@iwu.edu 
Course Description:
Whereas Optics in PHYS 106 considered only a few "sample rays," more powerful treatments consider the superposition of "many paths", and you want that kind of power! Our primary text, entitled Optics f2f: from Fourier to Fresnel, notes that "the essential insight of Fresnel was that all light propagation is [an interference phenomenon]." Fresnel's methods involve summing curved wavefronts emanating from each source point (and Fraunhofer's methods are simpler cases of Fresnel's). On the other hand, Fourier Optics involves summing plane waves. For all forms of interference (and hence all optical phenomena), phase differences between the contributing waves play a defining role, and so phasor diagrams will be stressed throughout.
 This course emphasizes handson instructional laboratory engagement supported by classroom discussion of mathematical modeling and the useful range of validity of various approximations. Labs begin with qualitative observation of polarization, followed by reminders of singleslit diffraction and multibeam interference that were encountered in earlier coursework  but now put to use to find the "filling fraction" of various Digital Optics devices. These examinations extend to inexpensive Digital Micromirror Devices (DMDs), to transmissive "Spatial Light Modulators" (SLMs) taken from classroom projectors, and (very quickly) onwards to (much more useful) reflective SLMs such as the LCoS chip shown above. Because these LCoS devices allow simple programmatic control of phase and/or amplitude (or polarization) within many local regions across the field of a beam of light, they serve as tools for direct exploration of the mathematical models contained in the text, while avoiding the excessive burdens associated with manual alignment and realignment (and realignment and...) that would be required for systematic studies based on traditional (fixed) optical components.
 Students engage in qualitative observation of aberrations, using handheld lenses, then "walking a laser" through "cloned apertures" on an optical breadboard, use shearplate interferometers to test collimation, and build "optical cloaking devices" as a means of teaching ABCD matrices. Again, SLMs allow direct control of amplitude and phase modulation of beams, which is useful for teaching Fresnel Diffraction, Fraunhofer Diffraction, and Fourier Optics, as well as spatial filtering, computergenerated Holograms, Aberration Correction, Laser Modes, and much, much more (e.g., encoding information, the linear momentum, spin angular momentum, and orbital angular momentum of light beams). As time and student interest allows, structured investigations should lead to exploratory conversations, and onwards to independent projects, such as the design and construction of holographic optical trapping systems, or opensource "DIY" advanced imaging systems for use in local research projects. Each station has a 6.5digit multimeter, a fibercoupled photometer, a highspeed oscilloscope, a lockin amplifier, and an RF supply for acoustooptic elements (for chopping or deflecting a beam), as well as steppermotorbased motion control.
 Prerequisites: students are expected to have completed an universitylevel introductory sequence in physics (e.g., PHYS 101102 or 105106) providing a basic introduction to geometric ("ray") optics, as well as coursework in the "Mathematical Methods in the Physical Sciences" (e.g., PHYS 304, which uses the text by Mary Boas) providing facility with matrix multiplication, the mathematics of complex numbers, vector operators (divergence, gradient, curl, and all that), and some introduction to Fourier transforms.
This course complements "Scientific Imaging" (PHYS 308), as well as "Quantum Optics: the Momentum of the Photon" (PHYS 317), a new course that provides further introduction to singlephoton quantum mechanics.
Reading material:
Perusing Sources that describe cuttingedge projects for your (electronically maintained) "Articles of Interest Log" is a key part of the course. You are required to add four new articles of interest each week, at minimum, to your log. This exercise becomes much more powerful when conversationally shared with others, and so such conversations are also required (and enter into your course grade!) You are encouraged to post notes on (or links to) projects of interest to any of our local student clubs:
The IWU SPS chapter is an open group. Membership in the national Society of Physics Students includes subscription.
The IWU IEEE student chapter is an open group. IEEE originally stood for the Institute of Electrical and Electronics Engineers, but the society has expanded its purview to become "the world's largest technical professional organization for the advancement of technology." National IEEE student membership includes: The Photonics Society.
The IWU SPIE student chapter is an open group. SPIE originally stood for the Society of Photographic Instrumentation Engineers but, like KFC, the acronym has been divorced from its origins, and the organization is now merely identified as "the international society for optics and photonics." National SPIE student membership is strongly encouraged, as SPIE does provide significant funds for the IWU student group if enough students at our institution join the national.
IWU has not yet established a student chapter of Optica (formerly known as the Optical Society of America, OSA). Historically, SPIE was oriented towards engineering and OSA was more academic; however, each society has evolved to the point where they are hard to tell apart. At most institutions, the Optica and SPIE student chapters are a single, combined entity, with the financial support coming from each national organization pooled to enhance awesomeness. So, national Optica student membership is something you may wish to encourage your peers to consider, as Optica does provide significant funds for student groups if enough students at our institution join the national.
Prepare For Each Lab:
There will only be two and a half hours of regularly scheduled lab time per week, but your activities must extend beyond this class time in order to achieve a desirable outcome.
Seek understanding of the appropriate reading materials before coming to lab!
Your laboratory notebook (maintained electronically or in handwritten form) should contain thorough sections covering each of the following areas, most of which require time outside of the regularly scheduled meetings (i.e., consider these tasks to be your homework for the laboratory portion of the course):
 Lab Notebooks, whether maintained electronically or in handwritten form, must be accessible by the instructor and TA, for examination. Your lab notebooks are graded each weekend and are officially due every Saturday morning, by 9 am. Unexcused failure to work on your lab projects during a given week, results in a significant penalty.
In grading your lab notebooks, I am looking for evidence of thought and analysis  and the degree to which you pursue clarity.
 Let it be clear: the course is called "Optical Physics," and not "Optical Engineering." The end goal here is not a product; instead, you are expected to maintain a focus on trying to understand the underlying principles (which will serve you well even if you go into engineering).
Grading notes:
Final course grades will very heavily weight your laboratory performance.
Written work in lab notebooks will be assessed according to whether or not it compellingly presents clear attempts at application of physical and experimental principles. That is, you are to engage in argumentative writing (attempting, at each level, to present a cogent argument).
Writing aimed at (working towards or) conveying understanding is key!
Week 
Readings to expect random quizzes on 
Handson Grapplings 
Pen & Paper Exercises  Computer Exercises  Links  
1 

Hurry to lab, for a QUIZ on implementing Ashley Carter's "Optics Rules to Live By!" Review notes on inclass handson demos: Rope Wave and Microwave Polarization with discussion of resistive losses Lab 0: Visible light polarizers, Birefringent Waveplates: prequel to Discussion of liquid crystals You might also expect inlab handson demos: Secret Monitors, 3D Glasses 
Pen&Paper HW #1 due Sept. 3: Exercises 1, 2, 4 from Ch 6 of Peatross & Ware Pen&Paper HW #2 due, start of class Sept. 5: Exercises 5, 6, and 10, 11 from Ch 6 of Peatross & Ware Plan your next steps, and schedule your time commitment for a productive week Philosophy Student become a Philosopher? at the RSO Fair!) 
I provide sample code written in IDL It is so readable it constitutes good pseudocode for those of you who prefer a different language. On a computer with a 2nd monitor, set to 1920x1080 resolution, I begin with two lines of code: window, xsize=1920, ysize=1080 tv, make_array(1920, 1080, /byte, VALUE = 128) This creates a window (that can either be programmatically positioned or simply dragged onto the 2nd monitor) and then displays an image with a uniform "grayscale level," where VALUE determines the brightness of each pixel (allowed values range between 0255, which is why the array elements were declared to have the "BYTE" data type). With the simple command given above, the "grayscale level" applied to all pixels is the same, but programmable: eventually, you will systematically vary this "grayscale level," to control the retardance of an optical device. Coding HW#1 due by 1:00pm, Saturday: Processing and Analysis applied to your own data from this week's LAB 
Here's a classic note by Jearl Walker, about how to make your own birefringent waveplates. of the same article.] 

2 

Lab I: "Diffraction Noise" & Filling Fraction of various devices 
Pen&Paper HW #3 due Sept 10: Optics f2f Ch 1: Exercises # 1.2, 1.6 
Are you set to use LabVIEW for image and video capture? Coding HW#2 due by 1:00pm, Saturday: Processing and Analysis applied to your own data from this week's LAB As a step beyond coding arrays with uniform grayscale level, consider these four lines of IDL code: GSL = 128 image = make_array(xpix, ypix, /byte, VALUE = GSL) halfpix = xpix/2 image[0:halfpix, *] = 0 
Embrace who we are: 

3 

Lab II: Part A: Alignment "Walking" a laser through "cloned" apertures, Beam expansion & Tests of collimation Part A': Aberrations Qualitative observation, using handheld lenses, + Discussion Part A'': Amplitude Modulation Direct writing of spatial patterns within a beam 
Pen&Paper HW #4 due Sept 12: Optics f2f Ch 1: Exercises # 1.10, 1.13, 1.14, 1.15 Pen&Paper HW #5 due Sept 17: Optics f2f Ch 2: Exercise # 2.1 (A multipart problem) 
Coding HW#3
due by 1:00pm, Saturday: Processing and Analysis applied to your own data from this week's LAB Read my IDL code: pistonbatch.pro, which creates sets of arrays with different grayscale levels 
This week in Lab: Explore how lens misalignments (e.g., tilt?, displacement from optic axis?, misplacement along optic axis?, etc.) yield distinct types of Aberrations in a beam expander or telescope. Be prepared to use the terms below to describe, on a QUIZ, these kinds of observations: Ray tracing credit: W M (Steve) Lee, now at The Australian National University 

4 

Lab III: Towards computercontrolled holograms: Calibration of Phaseonly Modulation You depend, critically, on keeping EVERY LITTLE THING organized! 
Pen&Paper HW #5 due Sept 17: Optics f2f Ch 2: Exercise # 2.1 (A multipart problem) Pen&Paper HW #6 due Sept 19: Optics f2f Ch 2: Exercises # 2.4, 2.5, 2.6 Pen&Paper HW #7 due Sept 24: Optics f2f Ch 2: Exercises # 2.7, 2.8, 2.9 
Coding HW#4
due by 2:30pm, Sunday: Analysis of your own data from this week's LAB Images are stored as arrays, where each element is an unsigned integer ranging in value from 0 to 255. Such elements are said to be of the "BYTE" data type. Sometimes your method for calculating an array might yield some OTHER data type. For example, "blaze.pro" is my code for creating a "phase profile" that is linear in some cartesian direction, ... but because I often ADD these phase profiles on top of other calculated phase profiles, and want to avoid rounding errors, the result is NOT converted to the BYTE data type, but is left as a "floating point number." Therefore, any array produced by this code will not be recognized as a valid image and therefore will not be displayed by a command such as "tv, image" in IDL. To fix this, add a line like the following: image = bytscl(image) Details are available online 
Imposing simple phase profiles can create and redirect multiple focal spots (which, if aberration is minimal, can act as Optical Traps, for micromanipulation of micro and nanocomponents, or cold atoms) A prism imposes local time delays equivalent to a linear phase lag Similarly, a lens is equivalent to a parabolic phase profile. For continuous wave illumination, we can write these phase profiles modulo 2π: Simple phase profiles can be added (modulo 2π) to place multiple foci in three dimensions. Note, too, that we can use such profiles to remove aberrations of the sorts you explored last week (e.g., due to displacement from optic axis, displacement along optic axis, etc.) 

5 

Lab IV: (Wavefront Modification) You will create plane waves, and curved wavefronts that travel along different directions by imposing simple phase profiles (and explore aliasing) & Computergenerated Holograms Version 1.0 (Noniterative algorithms) 
Pen&Paper HW #8 due Sept 26: Optics f2f Ch 3: Exercises # 3.1, 3.2, 3.4 
Coding HW#5
due by 2:30pm, Sunday: To explore what an SLM might do, create and display your own arrays: begin by imposing basic symmetries, each of which yields a distinct set of BASIS states: A linear phase gradient, in cylindrical coordinates, along the radial direction yields a Bessel beam ("drum head" modes that form, e.g., a basis set for all 2D wave physics with cylindrical symmetry). Here is my IDL code: bessel.pro A linear phase gradient, in cylindrical coordinates, along the azimuthal direction yields Orbital Angular Momentum, in beams called "LaguerreGauss" modes. Here is my IDL code: LG.pro Adding OAM and Bessel phase profiles yields "HigherOrder Bessel Beams" (HOBBs). Learning about such beams can unify much of what you've learned in other courses. A linear phase gradient along a cartesian direction (or superposition thereof) yields a plane wave deflected to some ANGLE (the basis of "Fourier Optics"). Here's my IDL code: blaze.pro A quadratic phase gradient yields a SPHERICAL wave (the basis for HuygensFresnel Optics). Here's my IDL code: lens.pro What might a cubic phase gradient yield? 
iHologram renders Fraunhofer holograms that can be used, e.g., for Holographic Optical Tweezers and for Computational Ghost Imaging and is now at Univ. of Bath 

6 

Lab V
: Diffraction & Interference (Redux) now using Amplitude Modulation to create Virtual Slits! 
Pen&Paper HW #9 due Oct 3: Optics f2f Ch 3: Exercises # 3.5, 3.6, 3.11 Pen&Paper HW #10 due Oct 8: Optics f2f Ch 5: Exercises # 5.2, 5.3, 5.4, 5.5 
Coding HW#6
due by 2:30pm, Sunday: Processing and Analysis applied to your own data from this week's LAB "Fringe Science" 
Charles Adams describes this simulation superimposing two copropagating waves of opposite handedness (Adjusting their relative phase difference will rotate the Polarization of the resultant wave): 

7 

Lab VI: Michelson Interferometer & Discussion of LIGO & Interference between a Reference Beam and a Shaped Wavefront (for several cases) 
Pen&Paper HW #11 due Oct 10: Optics f2f Ch 5: Exercises # 5.7, 5.8, 5.9 Pen&Paper HW #12 due Oct 15: Optics f2f Ch 5: Exercises # 5.13, 5.14, 5.15 
Coding HW#7
due by 2:30pm, Sunday: Processing and Analysis applied to your own data from this week's LAB 
Explore the effects of the radius of a circular aperture in this simulation from Optics f2f, showing both a transverse slice (i.e., the imaging screen view), as well as, a longitudinal slice (i.e., tracing out the beam propagation): Charles Adams provides a quick overview/perspective in his blog 

8 

Holograms
: Functional Holographic (Magic Cube) Keyboard, Diffractive Optic Elements, ComputerGenerated Holograms Version 2.0 (Towards Iterative algorithms), Holograms of Physical Objects (LitiHolo Kits & the magic of cut glass), Chess (Up)Sets 
Pen&Paper HW #12 due Oct 15: Optics f2f Ch 5: Exercises # 5.13, 5.14, 5.15 Pen&Paper HW #13 due Oct 17: Optics f2f Ch 6: Exercises # 6.1, 6.2, 6.3, 6.4, 6.5 Pen&Paper HW #14 due Oct 22: Optics f2f Ch 6: Exercises # 6.6, 6.7, 6.8, 6.9 (which simply asks you to write up Sect. 6.34, plugging in a few numbers for perspective). 
Coding HW#8
due by 2:30pm, Sunday: Processing and Analysis applied to your own data from this week's LAB 
Explore
online visualizations and the #PhysicsFactlet series tweeted by Jacopo Bertolotti of the Univ. of Exeter, such as this one: For all of his pedagogical visualizations, Prof. Bertolotti makes his Mathematica code available on Wikimedia Commons 

9 

Lab VII:
Dispersion studied using Digital Optics to create a virtual spectrometer 
Pen&Paper HW #14 due Oct 22: Optics f2f Ch 6: Exercises # 6.6, 6.7, 6.8, 6.9 (which simply asks you to write up Sect. 6.34, plugging in a few numbers for perspective). Pen&Paper HW #15 due Oct 24: Optics f2f Ch 6: Exercises # 6.10, 6.11 Pen&Paper HW #16 due Oct 29: Optics f2f Ch 6: Exercises # 6.18, 6.19, and Appendix B: Exercise B.3 
Dispersion (e.g., in a prism) and diffraction (as shown below in
a figure from Optics f2f) can both induce changes in the propagation direction of light. Explain why, with dispersion higher frequencies are deflected most, but for diffraction the higher frequencies see the least displacement. 

10 

Optical Cloaking:
a means of teaching ABCD matrices ABCD Matrix Tutorial 
Pen&Paper HW #17 due Oct 31: Optics f2f Ch 7: Exercises # 7.1, 7.7, 7.8 Pen&Paper HW #18 due Nov 5: Optics f2f Ch 8: Exercises # 8.1, 8.2, 8.3, 8.4 
Coding HW#9
due by 2:30pm, Sunday: Processing and Analysis applied to your own data from this week's LAB 
"Cloaking" device using ordinary lenses to hide objects across range of angles: 

11 

Lab VIII: Signal Processing in the Fourier Domain INVENT your own procedure before coming to lab! Ask, in advance, for any needed items This is your lab practical EXAM! 
Pen&Paper HW #19 due Nov 7: Optics f2f Ch 8: Exercises # 8.5, 8.6, 8.7 Pen&Paper HW #20 due Nov 12: Optics f2f Ch 9: Exercises # 9.1, 9.2, 9.3, 9.4 
Coding HW#10
due by 2:30pm, Sunday: Processing and Analysis applied to your own data from this week's LAB 
As described in this short blurb by Charles Adams, explore Temporal Coherence effects, using the slider at the bottom of this figure from Optics f2f: 

12 

Lab IX: Talbot SelfImaging Invent your own procedure before coming to lab! 
Pen&Paper HW #20 due
Nov 12: Optics f2f Ch 9: Exercises # 9.1, 9.2, 9.3, 9.4 Pen&Paper HW #21 due Nov 14: Optics f2f Ch 9: Exercises # 9.5, 9.6, 9.7 
Coding HW#11
due by 2:30pm, Sunday: Processing and Analysis applied to your own data from this week's LAB 
Scroll down within this pane for a celebratory discussion of Talbot SelfImaging:  
13 

Lab X: Phaseshifting Digital Holography & ComputerGenerated Holograms Version 3.0: Iterative algorithms & The Optimization Conundrum 
Pen&Paper HW #22 due
Nov 19: Optics f2f Ch 10: Exercises # 10.1, 10.2, 10.3 Summer Internship Applications (A required, graded exercise) 
Coding HW#12
due by 2:30pm, Sunday: Processing and Analysis applied to your own data from this week's LAB 

14 

Enter your analysis of the Optical Tweezers app (at left) into your lab notebook Pipe up (!) if you wish to supplement the simulation by constructing your own (live, handson) version of Optical Tweezers or Holographic Optical Traps 
Pen&Paper HW #23 due
Nov 26: Optics f2f Ch 10: Exercises # 10.5, 10.7, 10.10 
Coding HW#13
due by 2:30pm, Sunday: Processing and Analysis applied to your own data from this week's LAB 
Sometimes, information carried by light appears to be lost: If we are clever enough, there can be ways of recovering "lost" information: 

15 

Release Schrödinger's Cat! Mull over the concept of "Thing"ness 
Summer Internship Applications (A required, graded exercise) 
Remember, all information is physical: I'm interested in ways to recover information that appears to be dissipated during transmission. Wanna play? 

16 
Final Exam: Thursday, Dec. 12, 3:305:30PM Room E101 Center for Natural Sciences 
...You might be interested in discussing articles we've produced on these topics:
Your Dungeon Master:  Office Hours 

Gabe Spalding (wishing you grand adventure) 
(In CNS room C006B) Monday: 2:00  3:50pm Thursday: 2:30  4:20pm Friday: 2:00  2:50pm 
Grow the Conversation:
Our primary electronic form of communication is not email, but is via the Class Discussion Page on Piazza,