I was honored to speak at Moscow State University last week for the 60th anniversary of laser nonlinear optics. But in fact, the first nonlinear effects in optics were observed in the pre-laser era by Vavilov in Moscow in 1926! Here are some slides from my talk (thread).
Sergey Ivanovich Vavilov (Серге́й Ива́нович Вави́лов) was a giant of physics. He invented the term "nonlinear optics" in his 1950 book & was co-discoverer of Cerenkov radiation. Regrettably he died before the Nobel Prize for Cerenkov radiation was awarded in 1958.
Brown and Pike give the translation of how he introduced nonlinear optics in a chapter in the wonderful book Twentieth Century Physics (Eds Brown, Abraham Pais, A. B. Pippard 1995).
An excellent overview of how both Western & USSR-era optics developed post-laser is given in @jeffhecht 's fantastic article in @OPNmagazineosa-opn.org/home/articles/… The article includes the photo of the first self-focusing experiment that kicked off the study of spatial solitons.
Chiao, Garmire and Townes published the theory of spatial solitons in October 1964, which included the first statement of the cubic NLSE in optics and the sech-soliton solution.
But was it the first? In June 1965 Townes published a correction, acknowledging earlier work by Askarjan and Talanov. Reprints of these hard to find early papers are in the edited volume by @BoydNLOLab et al.
In December 1966, Akhmanov, Sukhorukov and Khokhlov published further independent theoretical studies studying the cubic NLSE, giving many references from Russian authors!
The experimental confirmation came from Bloembergen's group, and were published in December 1965. Bloembergen made sure to cite Askarjan and Talanov!
Akhmanov, Sukhorukov and Khokhlov published a long review paper in 1967 and established the Russian school of nonlinear and coherent optics.
Ahkmanov, Khokhlov and Bloembergen became friends, with mutual visits between the USA and Russia.
In 1967, Khokhlov & Akhmanov received the Lenin Prize, celebrated with a mural of them both riding a horse upon an SHG crystal converting red to green. It was on the wall for many years at Moscow State University. This photo is from @jeffhecht 's article. Where is the mural now?
Much early Russian work foreshadowed current areas of research that we are only just beginning to fully understand. For example, pulse buildup in mode-locked lasers.
Interestingly, the Dispersive Fourier Transform (DFT) technique which is now a key tool in measuring such laser buildup dynamics dates back to the 1980s - Akhmanov described the DFT stretched pulse as the "spectron"
Conclusion. Although the work at Columbia, Hughes, Harvard, Bell Labs & elsewhere was pioneering & vital to the technologies we now enjoy, we mustn't forget that the early days of laser and nonlinear optics were extremely international, and we owe all these giants our gratitude!
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Following up my rainbow thread, I starting thinking about the tertiary bow and indeed you can see it on a semi-transparent screen placed behind the glass sphere (i.e. in the same direction as the incident rays). The vertical metal post in the photo blocks the focussed light.
So the photo above shows simultaneously primary, secondary, and tertiary bows! Very nice. For completeness, I am going to now show some raytracing pictures for this case of all three caustics. First with one ray comparing ray paths in water and glass.
It is easy to scan over the incident angle (impact parameter y/R) and we can use false colour to show the caustics of the primary, secondary, and tertiary bows.
Preparing my 2025 Day of Light outreach lectures, I bought a glass sphere and made a rainbow. But I saw some odd things, and so here’s a thread with some photos & raytracing pictures to try to explain what's going on. First the basic setup showing the primary bow.
Where is the secondary bow? It took longer than it should have to find it, and it turns out it’s a long way away, nearly perpendicular. An angled screen helps and the secondary is then clearly seen with inverted colours as expected. But why is it so far away from the primary?
Moreover, fiddling with the alignment and moving the screen very close to the sphere, I can actually make the secondary bow appear inside the primary! What?? What is happening?
Feynman's QED: The Strange Theory of Light and Matter, was first published in 1985. In response to two completely unconnected queries in the last few weeks, here's a thread on how the lectures on which the book were based were first given in New Zealand.
The story begins in 1979 when Feynman gave the Sir Douglas Robb Lectures at the University of Auckland in New Zealand. These talks were a testing ground for his 1983 UCLA Alix G. Mautner Memorial lectures, widely considered to be the basis of the 1985 book.
But Feynman's Introduction to the 1985 book clearly explains that the lectures were first delivered in New Zealand.
This year is the 600th birthday of the University of Franche-Comté, the 10th university created in France in 1423. For @IDLofficial I gave a talk on optics history here since the science faculty was created in 1845. First batch of tweets follow; text in English, slides in French.
The story begins with our project with @SSAC_Univfc to save the lab archives that date back over 100 years. We found many old cans of photographic negatives from the 1970s and one was especially intriguing – who were these "ancestors"?
This single roll of film kicked off a 6 month study! It contained in it a photograph showing portraits of all the Chairs of Physics since 1845! (The dates in the photo show when they occupied their posts in Besançon.) Now for the detective work. Who were they?
Something different! Delighted to announce that a paper I wrote 22 years ago (!) on a supposed portrait of English scientist Thomas Harriot (c1560-1621) is finally online: TL;DR: Sorry but there's no real evidence that the portrait is Harriot ... 🧵 hal.archives-ouvertes.fr/hal-03839673
Harriot was a polymath. He produced the first telescopic drawing of the moon before Galileo, he discovered the law of refraction before Snell or Descartes, and he explored Virginia, learning Algonquian to translate. It would be nice to know what he looked like.
It was @libroraptor who first got me interested in Harriot. And even 22 years ago, books and websites were often reproducing a portrait from the University of Oxford which was “claimed to be” Harriot. This wording intrigued me, so I started to look into it.
To kick off the week, here is an updated (and long!) thread on the history of nonlinear optics. First a real surprise! The explicit use of the terminology “nonlinear optics” can be traced back to Erwin Schrödinger in 1942. Yes you read that right. Schrödinger himself!
Although this paper isn’t really what we would describe today as non-linear optics. Rather it describes “vacuum light-light scattering” or nonlinear QED. But the wording Schrödinger used definitely sounds familiar! It builds on earlier work by Born, Infeld, Euler.