Archive for the 'Optics' category

My talk on "Forgotten milestones in the history of optics"

Mar 18 2010 Published by under History of science, Optics

I just got finished giving a talk to the graduate students of my department on "Forgotten milestones in the history of optics".  The talk seemed to be very well-received, and I've already had faculty suggesting that I should give it again in the engineering department.

The talk was scheduled at 1 hour, and I prepared 45 slides.  My only miscalculation was that I didn't take into account how long-winded I get when I'm talking about a subject I'm really passionate about -- I ended up speaking for 1h10m!

Here is the presentation:  2010_historyofoptics

Three of the four topics are essentially adapted from history of science posts I've put on this blog before, though the first one -- on Ibn al-Haytham -- is new.

If any departments are interested, I could be coaxed into coming to give a presentation... 🙂

12 responses so far

A new optics blog: Internal Reflections

Mar 11 2010 Published by under Optics

There's a new optics-related blog out there!  A friend and colleague sent me notice that the company he works for, ASE Optics, has started its own blog, called Internal Reflections.  Quoting their "about" page,

This blog is a place to share our thoughts on the science and the business of optical engineering.

As it stands, they've only just begun, but already have a nice short post on “Productive Stupidity” or “Failure Is the Only Way to Win the Nobel Prize”.

I'm normally a little hesitant to follow industry blogs, but I know the folks at ASE Optics and expect to see some interesting stuff from them in the future.

(Note: For the conspiratorial-minded, I received no compensation for this post, other than Damon's promise to contribute to The Giant's Shoulders!  I will hold him to that.)

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Rolling out the (optical) carpet: the Talbot effect

Mar 04 2010 Published by under Optics, Physics

ResearchBlogging.orgOne of the wonderful things about having a career in science is that a deeper understanding of the science leads to a greater appreciation of its beauty.  In physics, this usually requires a nontrivial amount of mathematics, but there are some phenomena that are self-evidently beautiful; unfortunately, many of these are also not very well known!

In working on my textbook on optics, I delved rather deeply into one of these phenomena, known as the optical Talbot effect.  First observed in 1836 by Henry Fox Talbot, the effect went unnoticed for nearly fifty years before being rediscovered by the great Lord Rayleigh in 1881. The true subtlety of the phenomenon was still not understood, however, for another hundred years!

In short, the Talbot effect can be described as the self-imaging of a diffraction grating: at regular distances from the grating, the light diffracted through it forms a nearly perfect image of the grating itself. This simple statement does not do justice to the Talbot effect, however, which results in stunning images such as:

This is an example of what is known as a Talbot carpet,  presumably because it is reminiscent of an ornate Persian rug:

(Why isn't it called a "Talbot rug"?  That I can't answer.)

There's a lot to explain in order to understand the significance of the Talbot carpet, starting with an explanation of what exactly a diffraction grating is!

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8 responses so far

Announcing: Mathematical Methods for Optical Physics and Engineering!

Feb 10 2010 Published by under Optics, Personal, Physics

I've mumbled various random things in the past about my upcoming textbook project; this week, I finally got approval from the publisher to start hyping it on the blog.  (Actually, they never prohibited it, but I just got around to asking them last week if it was okay.)

Announcing:  Mathematical Methods for Optical Physics and Engineering, by Greg Gbur, to be published by Cambridge University Press!  The raw image that I have submitted to be turned into beautiful cover art is shown below:

(I'll leave it for the readers to guess what the image represents; feel free to speculate in the comments.)

There are plenty of "mathematical methods for physics" books out there -- why did I feel the need to write another one?  Well, I've been teaching a graduate course on mathematical methods in my department for five years -- and actually taught one while still a grad student, too.  My department focuses on optical science and engineering, so most of the students I get are (a) interested specifically in optics, and (b) often coming from an engineering background with much less abstract mathematics.

Most mathematical methods for physics books are geared towards a general student of physics.  This was a bit irksome for both me and the students while I taught the class, because optics requires a slightly different set of mathematical tools, in particular more emphasis on signal processing, integral transforms, and Green's functions.

Furthermore, math methods books typically draw from a wide variety of physical topics for exercises and examples.  This is, in my opinion, sometimes futile -- for most students, examples drawn from general relativity (or even statistical mechanics) are no better than abstract mathematical ones.

Optics has become a significant field of science in its own right, with dedicated schools in Arizona, Rochester, Orlando, and Charlotte (my home base).  Plenty of other departments of physics and engineering have a strong focus on optical science.  I decided to take a stab at revising the curriculum for those optics-centric programs, and introduce my own mathematical methods book that would complement an optics undergraduate or graduate education.

One of the biggest problems in teaching mathematics is making the connection between the math itself and the application of said math.  To try and address this, (almost) every chapter begins with an introductory application for the technique to be studied, and ends with a more detailed study of how the math is used in solving an optical problem.  I've tried to pick optical problems that don't typically appear in other optics textbooks, for instance: the Talbot effect, Zernike polynomials and aberrations, optical vortices, X-ray crystallography, computed tomography, and even optical cloaking!  I've also taken the unusual step of including essay questions in the exercises: read a given scientific paper and answer questions about its relation to the given mathematical topic.

Though academic optics programs are becoming more common, I'm hoping the book will catch the attention of instructors teaching general math methods for physics courses.  I've tried really hard to approach many of the traditional topics from a slightly different angle.  I'm endeavoring to pass through a very narrow opening between "qualitative understanding" and "mathematical rigor" -- I only include the rigor when it genuinely helps in applying the given methods.

I've also tried to make this book a little more portable!  Most math methods books are well over 1000 pages, but mine is targeted at 850.

Obviously, this book won't be for everybody, and probably won't appeal to many of the readers of my blog, for instance those interested in non-technical explanations of optical phenomena!  (This project was conceived long before I started a blog; my next writing project will be a more popular science/history book.)  Hopefully everyone will benefit from my efforts, however -- over the next few months, I'll write non-technical descriptions of many of the optics examples that I've used in the book.  I'll also give more descriptions of the book and the process of finishing the book at time progresses.

16 responses so far

Kepler's contributions to optics, at Renaissance Mathematicus

Dec 28 2009 Published by under History of science, Optics

Those who follow this site for optics and history of science posts should take at look at this nice post by The Renaissance Mathematicus.  It covers the contributions of Johannes Kepler (1571-1630) to the modern theory of optics.  Kepler is most known for his astronomical observations, but optics and astronomy go hand-in-hand, for obvious reasons!

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Reversing optical "shockwaves" using metamaterials (updated)

Nov 20 2009 Published by under Optics

ResearchBlogging.orgIn a recent issue of Physical Review Letters was an article with the intriguing (to me) title of "Experimental verification of reversed Cherenkov radiation in left-handed metamaterial," by a collaboration from Zhejiang University in China and MIT.  The paper is an experimental verification of an effect predicted for metamaterials way back in 1968 by the originator of metamaterials research, Victor Vesalago, in his original paper, "The electrodynamics of substances with simultaneously negative values of ε and μ."

Čerenkov radiation (I prefer this spelling) is an effect analogous to the sonic boom created by projectiles moving faster than the speed of sound.  Čerenkov radiation is emitted by ultra-high speed charged particles moving in matter.  In ordinary matter, this radiation travels along the direction of motion of the particle; in a negative refractive index material, Vesalago predicted that Čerenkov radiation will travel in a direction opposite of the direction of the particle. Now, we have some preliminary experimental evidence supporting this prediction.

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6 responses so far

Boo! The optics behind "ghost" imaging

Oct 31 2009 Published by under Optics

ResearchBlogging.orgHalloween seemed like the perfect time to talk about an unconventional sort of optical imaging, referred to as "ghost" imaging.  I should point out at the beginning, however, that I'm not talking about this sort of ghost imaging:


Don't get too disappointed, however!  Ghost imaging is in fact a fascinating and relatively new technique in which a detector can produce an image of an object that it cannot see!  The physics behind this effect is somewhat subtle, and resulted in at least one minor controversy since its introduction.  Let's take a look at it...

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2 responses so far

Frontiers in Optics: T,W,Th

Oct 17 2009 Published by under Optics, Science news

One of the things that happens to me as the years go by is that I spend less time at meetings listening to talks and more time talking to friends and colleagues and planning new research collaborations.  From discussions with said colleagues, I get the feeling that this shift in emphasis is not unique to me.  (I suppose this is why young professionals make better conference bloggers.)

So for my discussion of the last three days of the conference, let me just point out a few general observations that I had while attending.

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4 responses so far

Other blogging of Frontiers in Optics

Oct 14 2009 Published by under Optics, Science news

By the way, if you're looking for other blogging about the Frontiers in Optics meeting, there are 3 official  bloggers this year, and they can be read here.  I actually know Adam and Bob, and I'm absolutely convinced they're trying to muscle in on my turf!  I'm posting a mental note to crush them sometime in the future...

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Frontiers in Optics: Monday

Oct 14 2009 Published by under Optics, Science news

The main "act" on Monday at the conference was the Plenary Session/Awards Ceremony.  Lots of scientists I'm familiar with (and whom I've met at one point or another) were given awards, including Joseph Goodman (known to students for his books on Fourier and statistical optics), Anthony Siegman (known to students for his Lasers book), and Roland Winston (a pioneer in the development of solar concentrators).  Victor Vesalago, whose 1968 paper on negative refractive index ushered in the era of metamaterials, was given an award for this contribution.  (I was surprised; with apologies to Dr. Vesalago, I always assumed he was dead.)  The OSA Student Chapter of Laval University won an award -- if only there was somebody from Laval here at the meeting that I could congratulate!

Roy Glauber, who was a joint winner of the Nobel Prize in Physics in 2005, was awarded honorary membership in the optical society.  He gave a charming short speech in which he described his early (pre-age 14) experiments in optics.  Among other things, he built his own refracting telescope, and thought for a while that he had discovered "rainbows on the moon"!

Although the Physics Nobel this year went to three optics researchers, and Society members, none of them could come to the meeting.  Apparently a podcast with one of the winners is available on the OSA website, but I haven't been able to dig it up yet.

The winner of the Frederic Ives Medal (the highest award conveyed by the society) was Robert L. Byer, a pioneering researcher in laser technology.  He gave a very nice talk about the historical development of the laser, from devices which could produce milliwatts of power with an electrical to light conversion of 0.2% to current devices which can produce megawatts of power and have 70% conversion efficiency.  Such powerful lasers have applications which are both practical and scientific.  On the scientific size, such powerful beams are to be used to accelerate electrons to ultra-relativistic speeds at the SLAC linear accelerator for particle physics research.  On the practical side, such beams are being used in attempts to generate nuclear fusion, at the National Ignition Facility.  Such attempts have been going on for years without success, so it was eyebrow-raising to hear that they think that they will actually achieve fusion in October of 2010!  If accurate, the implications for the world's energy needs is huge.

The first plenary lecture was by Andrea Ghez, an observational astrophysicist at the University of California at Los Angeles.  Her talk, "Unveiling a supermassive black hole at the center of our galaxy," was quite fascinating.  Certain galaxies, known as active galaxies, radiate massive amounts of energy, a process which we are confident is due to mass accretion by one of these supermassive black holes (SGHs).  But active galaxies are rather uncommon, which raises the question: do all galaxies have SGHs in their center, just "quiet" ones?  Our own galaxy is the best place to look, since we're obviously in it.  The trick is to look near the very center of the galaxy.  An SGH would be an object with 4 million times the mass of the sun in a very tiny, planet-size or smaller area.  By looking at the orbit of stars near the galactic center, one can estimate the amount of mass at the center and a lower limit of the area contained by that mass.  Work by Ghez has shown that 4 million masses of the sun is contained in an area the size of the solar system; this is not quite small enough to prove that it is a black hole in the center, but it is unlikely to be anything else at that scale.  Future experiments to make more precise measurements will require larger telescopes, with even staggering 30m aperture telescopes proposed!  (The Keck observatory has a 10m aperture.)

The second plenary was a talk on X-ray microscopy by Janos Kirz.  It was interesting, but couldn't compare to black holes, and I found my mind wandering during the talk and myself not recalling much of the details.

Later in the day, I went and listened to Victor Vesalago's talk on negative refractive index.   There was nothing much new in the talk -- the original research was done 40 years ago -- but it was really neat to hear the original "inventor" of negative refraction describe his ideas.

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