Welcome to LOPE at University of illinois at Urbana-Champaign
Professor James Gary Eden and Sung-Jin Park
Laser and microcavity plasma applications
The website of the Laboratory for Optical Physics and Enginnering (LOPE). We are dedicated to the pursuit of new and efficient sources of visible, ultraviolet (UV), and vaccum ultraviolet (VUV) radiation. LOPE people have developed novel laser spectroscopic techniques and devlopment of microcavity plasma devices and their application.
The new Zacuto PlaZma Light
by Joseph T. Verdeyen  (Click to show/hide...)
The Gaseous Electronics Laboratory was started in 1950 when Dr. Ladislas Goldstein joined the Department of Electrical Engineering after a very productive career at ITT Research Laboratories at Nutley, NJ. This was a significant phase in the Department's history in that this was also the period when the Department also attracted Paul Coleman and John Bardeen, and of course, John changed the course of the world to say nothing of the Department. A bit of the history of Prof. Goldstein is most interesting (and has a 60% probability of being true):
- He came from Hungary to France to study Physics in M. Curie's Laboratory and supported himself during his graduate career playing professional football (European Style). As a consequence, he had an amazing ability to "kick" virtual anything into any desired target - graduate students being the exception. As Graduate students, we would leave wads of paper on the floor for him to kick into the nearest garbage can when he thought we weren't looking. He also indicated that he learned French by ushering at the theater and copying the diction of the actors.
- One of his first jobs at the Curie Laboratory was to tip off the flask collecting the Radon emerging from the nuclear decay of radium. He did this without any protection since much of the heath hazards were not yet identified (or maybe believed). One of long term effects was that he switched fields from Nuclear Physics to Gaseous Electronics. He related one incident that illustrates some of the carelessness of the times: Their Vandergraph generator kept arcing to the ceiling and to solve the problem, the placed open pans of carbon disulfide to increase the electron attachment and increase the dielectric strength of the air. While that practice was discontinued, that experience was one reason for the open bay design of the Gaseous Electronics Laboratory built in 1962.
- He finished and defended his thesis one week before Germany invaded France and being Jewish decide that Paris was not the best place to be and started for the coast heading for England. During that trip, he was fired upon by a German sniper and hit! Fortunately, the bullet was stopped (or passed through) a can of sardines resulting in a slow drip of a sticky liquid. He first thought that he was bleeding but was very happy to find otherwise.
- Prof. Goldstein was very formal in his relations with the graduate student and other faculty members. For instance, he always addressed me as Mr. Verdeyen while I was a graduate student, Prof. Verdeyen after I graduated and joined the faculty, and finally "Joe" on the day he retired and left for France.
- Prof. Goldstein retired in 1972 and died in France in the summer of 1995.
For those who are not familiar with the TR switch in radar, let me explain: Most radar systems use the same antenna for the transmitter (kW to MW) and receiver (sensitivity = nW to pW). The TR switch uses part of the transmitter power to ionize the gas in a cavity in front of the receiver which de-tunes the pass band of the cavity from the transmitter's frequency and thus protects the sensitive receiver. There was always a small "spike" leaking through and this could wreck the system. To analyze and quantify this "spike" was one of the first research problems addressed by the laboratory.
There is a very interesting ionospheric phenomena, the Luxemburg Effect, that was exploited in the early days of the laboratory and was a precursor of many perturbation techniques now used in many fields. Telegren was the person who discovered the effect, namely that Radio Luxemburg would heat the electrons in the ionosphere and thus transfer the audio envelope on its signal to any wave traversing that portion of the ionosphere by modulating the absorption. Prof. Goldstein exploited and expanded this phenomena in the laboratory to identify and quantify many electron temperature dependent processes such as e-i recombination, electron-ion collision frequency, and any other electron collision process. He used to microwave signals, the "heating" wave and the "sensing" wave to examine these processes in the decaying portion or "afterglow" of a pulsed discharge. One of the unique modifications was to subject the plasma to a static magnetic field so that the electrons were in cyclotron resonance with either wave. All sorts of nonlinear phenomena from harmonic generation to modification of rate processes could be observed with relatively small microwave power (횇 200 mW or less).
In the late 1950's, research on controlled fusion was declassified and the Laboratory broadened its viewpoint to include this highly ionized that might be found in a fusion reactor as well as in shock waves associated with a re-entry plasmas. At that time, Prof. Golstein was assisted by Prof. A. A. Dougal (now at the University of Texas at Austin), Prof. Julius Cahn (Prof. (Emeritus) in Astronomy at U of IL), Prof. C. D. Hendricks (Emeritus of ECE at U of I and a major player in the US effort in the laser driven pellet fusion effort at Livermore), and Prof. Thomas Marshall (now at Columbia) who helped the lab start the quantum physics work in Gaseous Electronics by the study of ESR and NMR of neutral species resulting from the discharge.
After the invention of the laser, much of the Laboratory effort shifted into the Quantum Electronics Area and slightly away from plasma physics. The route followed for that change is interesting in that global plans failed but dumb luck prevailed. Let me illustrate.
Although we had plenty of experience with microwaves, its applicability to the high density theta-pinch plasmas was small at best and thus we were forced to use some rather painful diagnostics such as "Stark Broadening" spectroscopy to infer the electron density in space and in time. While modern instrumentation has made that technique easy, it was most painful in the early 1960's. There were two approaches followed by the lab: to use the the Thompson scattering of ruby laser light from the electrons and ions measure the electron density and temperature and if we were lucky we could also get the ion temperature. As it turns out, T. V. George did verify Rayleigh scattering cross-section and, after much money and a lot of effort, H. Merkelo did get the Thompson scattering to work but after the contract ran out and thus we were never able to exploit it.
During the course of that work, Goldstein got a request-for-a-proposal which was to be classified (still allowed at that time), and because of that issue, J. B. Gerardo and J. T. Verdeyen, who had security clearances, were asked to research the issues and write the proposal, which we did. We were very dismayed when a new RFP came out using many of our ideas but require its performance in a government lab.
We did not get that contract, but Jim Gerardo and I got interested in the laser area and were determined to improve our frequency capability by moving the decimal point and started on laser interferometry. At that time, we only had three dielectric coated mirrors, 2 curved ( 100cm radius) and one flat, and no laser tube. So we made a He:Ne tube with microscope slides for windows for operation at 1.15 microns and decided to couple the laser to an external cavity in which the plasma was located. We had some mistaken ideas about Fabry-Perot cavities and in any case we only had one extra mirror, a curved one, and thus had to make the flat serve a dual purpose. We had a dim view that maybe the plasma cavity should be confocal but had no logical reason to justify that choice other than the plasma did "fit" in the 50 cm space. Gee, we got some beautiful fringes when the theta -pinch was fired in that cavity but a fringe count predicted a electron density a factor of 4 higher than that inferred from Stark Broadening. Eventually, we realized that the extra factor of 4 came from the spacing between the transverse modes of the external cavity and thus this coupled cavity interferometer was a factor of 4 more sensitive than the conventional FP system. This approach was successful and led to quite few other contracts and many publications.
When Prof. Goldstein retired in 1975, Prof. Joseph T. Verdeyen was appointed Director by the Department Chairman, E. C. Jordan and remained in that position until August, 1994 when he retired and Prof. J. Gary Eden was appointed Director by T. Trick.
There have been many faculty associated with the laboratory and their current position and approximate location are given below:
|A. A. Dougal||Prof. (Univ. of Texas)|
|C. D. Hendricks||Prof. (Emeritus, U of I); Lawrence Livermore Labs|
|J. Cahn||Prof. (Emeritus, U of I)|
|T. C. Marshall||Prof. of EE at Columbia|
|B. E. Cherrington||Prof. University of Texas at Dallas|
|H. Merkelo||Assoc. Prof., ECE, U of I|
|T. V. George||Department of Energy|
|J. T. Verdeyen||Prof. (Emeritus, U of I), but still harassing the troops|
|J. Gary Eden||Prof.,ECE, Director of the Lab|
|M. Kushner||Prof. ECE, U of I|
The laboratory has sponsored over 85 PhD thesis' and supported over 150 MS efforts. It has such a wide and diverse history that many groups check with us for borrowing (or stealing if they can get away with it), or to find if we still have a stock of some discontinued vacuum tube. We may have although our stock is decreasing. As one student remarked, this lab has 2 of every device ever made (and probably needs repair).
The Lab is famous for their athletic ability and usually stomp the candy-ass semiconductor groups into the ground unless many of them go together and come up with an all-star team. We also meet on some Fridays at Murphy's for a beer or a coke and political or scientific discussion. Indeed, one of our graduates, Dr. Gary Johnson sends $5-10 each year to support a St. Patrick's Day celebration for which every one is grateful.
The lab is also well known for its relaxed atmosphere, easy give-and-take on almost any subject, famous goofs, and good natured jokes on JTV on St. Patrick's Day with examples of the latter two given below.
- When Blake Cherrington was in the Lab, he almost always wore an orange shirt to off-set JTV's wearing of the green.
- Wired up the John with a telephone which rang just as JTV was trying to catch up on the literature. Of all persons, it was Al Wilson who ask "What'cha doing little buddy".
- Papered the door-way closed while JTV was in the John.
- Filled up his car with newspaper.
- Constructing and then hiding four pulsed oscillators which went off at random intervals from 4 different locations in JTV's office.
- Filling the coating tubes from the Polaroid film with dry-ice, capping with tape, and storing them in LN2 until I came back from running. Then placing them in the waste-paper basket, the desk and other places in my office to "expand", rather quickly, while I was eating my lunch.
- Running with JTV while singing "Ol Danny boy". It wasn't the bad singing, but rather the realization that they could run and sing while I was gasping for air.
- Hiding a full case of beer behind books, in drawers, and in file cabinets. I am not sure that I have found all of them yet.
There were two famous goofs made on the same day when JTV referred to Fabry and Perot as two French men from France and Gary Eden referred to a Coal-fired Nuclear power plant.
The lab is continuing to evolve and I am sure that Gary Eden will keep it the fun place to work that it has been for the last 46 years.