Idle Diffractions

An Update on The James Webb Space Telescope

T – 7.5 π x 10⁷

Last week found me at, among other things, the NASA SBIR conference on mirror manufacturing.  The main attraction being the last day visit to the Goddard Space Flight Center (GSFC) to see what can be seen of the integration and test of the mirrors and the instruments (NIRCAM, NIRSPEC, MIRI, and FGS).  There is encouraging news.  It does appear that most of the hardware now exists for both the telescope and the instruments.  Each of the instruments arrived at GSFC during this year and they are in some phase of initial testing.  GSFC is the facility where the thermal and vibration testing will occur as well as integration and testing. 

At the conference, Glatzel (yes, the son of the optical designer who inspired Juan Rayces optical design algorithm, found in Eikonal) reported that Tinsley (the L3/SSG version, not the ZYGO/ASML version) has delivered the last of the mirrors and yes, they are defining the state-of-the-art.  The numbers are not yet packaged for public dissemination, but, they are impressive. 

Now, what about that title?  I have no idea how many of you know that the number of seconds in a year is conveniently close to the number π x 10⁷ (365x24x60x60=31,536,000), something that was pointed out to me back in undergraduate days.  So, although it did “feel” like the JWST is moving out of the one challenge after another (which can be fun, but expensive) phase and into the relatively routine.  This probably not quite the case, but, the project does appear to have moved to an important to phase.  Below is a shot of one of the spare segments in a GSFC clean room (a really big one, as are most of the facilities at Goddard.

 

A spare segment from the JWST.

Following the center tour, Joe Howard, working with the host Phil Stahl and Peter Blake arranged for the group to see the “Science Sphere”.  This is pretty fun.  It is a suspended sphere, about 4-5 ft in diameter that forms for the screen for 4-6 projectors that are nicely integrated.  Perhaps most impressive, the projectors can be fed by real-time data.  There is the weather, including for example the worldwide weather in the summer of hurricanes, including, of course, Katrina.   But, the most compelling was to watch the air traffic world-wide, in real-time – fascinating (and then we had to catch the airplane).  One of the colorful earth resource images (somewhat fuzzy due to the lighting and motion) is below.  If you get near the GSFC visitor center, be sure to arrange to see The Sphere.

 

An image from “The Science Sphere” at the GSFC Visitor Center.

Faster, Smaller, (Higher), but, Maybe not Cheaper

Report from Laser Munich

I was at Laser Munich last week, again.  And, again, it seemed that Europe is continuing to emerge as a hotbed for optics.  Laser Munich makes other similar conferences in the U.S. look, to be generous, anemic.  I consider this good; it seems to be reinvigorating the field (at least for us classical optics types).  I only made it to half of the exhibits and 1/5 of the posters, but, in that I saw many things of interest.  As always, things seem to be going towards faster (femto is becoming atto), smaller (nano is almost a standard), and more complex (freeform is everywhere, even if we cannot measure it).

 

The Synopsys spread at Laser Munich.  There was a definitive “race for the top” (e.g. ceiling), which it appears that we won.  A nice touch came at the end of the day when some key vendors, including Melles Griot, conveniently next door, would bring in cases of German beer and one evening a vendor even brought bratwurst for dinner (perhaps unfortunately for them, I never figured out who the vendor was, unless it was the conference itself).

There were two major technical conferences of interest to me (this is where EOS, SPIE, and OSA all sponsor technical conferences).  The first was the EOS conference on Manufacturing of Components in combination with the SPIE conference on Metrology.  Here, some of the latest thinking in how to manufacture and measure (still unsolved) freeform surfaces was at the center of the discussion.

The other conference was, as was the case two years ago, the OSA/SPIE conference on OCT (optical coherence tomography).  This year was as excellent as the last, with one of the fastest overviews of 20 years of technology I’ve ever seen, presented by Prof. Drexler and an excellent tutorial by the founder of the field, Prof. Fujimoto.  To me, this is one of the most interesting cases of combining a shopping list of the courses that are taught in graduate school and from that emerges a technology.  It uses interferometry (white light Michelson), exotic sources (femto lasers, super continuum, super luminous diodes (I wonder what will be the adjective after “super”, ultra perhaps? – we’ll see), high resolution spectrometers, Fourier transforms, and a lot of tricks, developed over 20 years to create, recently, images of layers under the skin. 

While OCT is aimed at axial (1-D) resolution for application to the eye, OCM (optical coherence Microscopy) is directed at collecting images in 3D of cells under the skin.  The University of Rochester is the first to develop subcelluar 3D microscopy, biopsy level images in a configuration that can move to the clinic.  The latest image, acquired last week in the latest configuration, is shown below.  This technology has one of the fastest growth curves ever seen and demonstrates that exponential growth in technology is continuing to sprout up all around us. In optometry, the first clinical use was 2002, and since then it has grown to approaching 10 million procedures, at $48/each.  This would make a nice topic for Harvard Business Review.   One of the UofR recent images, which represents the state of the art, is included below, courtesy of Prof. Jannick Rolland, the Brian Thompson Chair Professor of Optical Engineering at the Institute of Optics.  These images are created through the application of optical engineering to advance complex ideas in science, an ongoing theme.

 

No scalpel was involved in acquiring these images of cellular structure under the skin.  Article currently posted in pending publication in Optics Letters.

P.P. Ewald?

I happened to need to learn something about X-Ray diffraction the other day and this led me to one of the unheralded (at least in my circles), P.P. Ewald.  Prof. Ewald, based on a semibiographical book on him and his accomplishments edited by D.W.J. Cruickshank, P.P. Ewald and his Dynamical Theory of X-ray Diffraction should be a household name in physics it would seem.  He was a student of Sommerfeld and is commonly associated with the likes of Hans Bethe in addition to living to 97 and clearly was well liked by his colleagues.  All of these features lead me wonder why, for example, I know of Bragg so well, but know nothing of Ewald who in many ways appears to have brought the graphical, mathematical conceptual context to a field of science that has generated more than 10 Nobel prize winners and was the foundation of key work by a cast of hundreds, including the likes of Bragg, Brillouin, deBroglie, von Laue, Lorentz, and many more of the household names of physics in the early 20^th century. 

The reason may be that only the names above and others in that league were able to comprehend and then leverage his work.  At least based on the book, which I would expect is a remembrance of the good times and glorification of the bad, Ewald was nothing short of a visionary.  He was one of the rare, like Feynman, who thought graphically.  It is clear that mathematics, no matter how complex became parametric plots in his world.  His first contribution was, as is sometimes the case, truly revolutionary.  It was a graphical view, in 1912, of a physical process that even today eludes us, birefringence.  His classic figure is below.  And, no, I cannot really explain it, yet.    I do know that even now, optical ray trace codes cannot directly handle the analysis of a birefringent material in all its aspects, including for example polarization.  Yet, Ewald, before X-rays were even discovered, was developing a fundamental graphical view of what they would do when they were discovered. 

I am continually amazed by the period from 1885-1930.  It was a time like no other in science.  With the recent accessibility to the original material of this time, it is becoming increasingly valuable to research the original works.  As much for what they say, in a simpler time, as for an understanding of how they were thinking.  Although much earlier, last week I was able to add the works of Thomas Young (yes the double slit experiment) to my library.  Written in 1807, one can only be amazed at how much original science he both conducted, but, simultaneously published.  In reading of Ewald, one struck by how the struggle of everyday life for him and his family is lost in the triumph of the science.  The most striking for me is the photo below. AFTER, completing his PhD that anticipates the science of X-rays, and after the discovery of X-rays, a photo from the book shows Ewald at the reins of a four horse power (literally) carriage, which was a “portable” X-ray machine as he embarked for the Russian front.  It is very difficult to realize that the same calm professor in pictures from the 1970s is the same person as the one driving off to THE war.

Figures from P.P. Ewald and his Dynamical Theory of X-ray Diffraction, Ed. D.W.J. Cruickshank, H.J. Juretschke, and N. Kato, Oxford Science Publications and The International Union of Crystallography, 1992