Remembrances of Conrad Phillippi

Bill Woody:

Conrad Phillipi spent his early years within the AF Research establishment at Eglin AFB.  My understanding was that Conrad did spectroscopic research on targets, backgrounds, and aerosols related to weapon missile development. This research was not specifically on the weapons themselves but was more related to the environment for operation.

 

Later Conrad sought and found a position within the Materials Laboratory, in the System Support Division I believe, continuing analytical spectroscopic work related to Failure Analysis.  Should I receiver further information from the family, I will update this paragraph.

 

I joined the Laser Hardened Materials team in Sept 1981.  Conrad was part of the New-Technology Team as the innovative thought leader.   He had joined the team at the request of Gary Denman the branch chief at that time.  I believe that Conrad had started as part of the laser effects team (1975-78?) of the Laser Hardened Materials (LHM) team.  This included joining the team that was establishing the LHMEL (Laser Hardened Materials Evaluation Laboratory) Laser Test Facility in B 71.  Here he worked on all aspects of the test facility as well as conducting research on Laser Effects on Materials.   

 

Conrad then became the innovative thought leader for Sensor and Eye - Laser Protection Technologies.  In this role, Conrad led a team which generated and explored new hardening concepts; started new in-house efforts and new contract activities for a wide diversity of optical devices, sometimes electromechanical contraptions (his words) and the most innovative solutions in the country.  Some are still in development for practical solutions today.  Several have found broad application in the past 40 years.

 

My first memories were of two national meetings in 1982, one hosted by the LHM team and Conrad with a high-powered group of academic professionals.  Conrad described the problem, the difficulty of the problem, and this generated a report of new approaches to deal with difficult sensor protection technical issues of the program which were not being addressed at that time.  The second meeting was hosted by DARPA seeking approaches to the same difficult problem, and it was at this meeting when the concept of Rugates was first publicly presented and discussed by Conrad and Walter Johnson also of the LHM Team. 

 

One of the academics at the DARPA meeting stated;  “You have certainly picked a difficult problem……and, a very difficult solution.” He later (in that day) commented, “I now understand why” and later at the same conference, “now that I understand the problem, I have a few thoughts to contribute to the solution.”  This was Angus Mcleod of University of Arizona Optical Sciences Center.  Angus was the leading academic in thin film optical filters in the United States, and continued to be a friend of the LHM team for many years. Some industrial scientists also claimed to finally understand the larger problem and why the Rugate technology was so innovative and critical, and they went home to work the problem, as did our team in the LHM group.

 

It was indeed a most difficult technology.  It would occupy some of the most brilliant engineers of the US industrial base.  One of them, Bill Southwell, whose contributions to optical devices and systems go far beyond Rugates, said when I first met him: “I got the (classified) paper from the DARPA meeting late in the day. It was attached to the request for proposal, members of our team had attended the presentation; they were excited, but I thought ‘nothing new!’ But I opened the paper at quitting time, and I was still at my desk after 10:00 pm, I could not put it down.  Many designers had thought of such a concept, sine waves, but NAH, ’too difficult’.   But Conrad and his team had assumed that it was possible to produce and extended the concept to many other things that became possible if it were doable! (producible). It is the most conceptually simple thing that expanded the realm of possibility beyond anything ever conceived.”  The paper presented at the “closed” DARPA conference showed many of the things possible which no one had ever imagined, simply because of the assumed difficulty of fabrication.

 

Today, three industrial teams can make these filters and have transitioned them to many applications of the military.  Applications to-date include Direct-view optics, Airborne sensors of all types, Eyes, many space applications, and have enabled improvements to core basic operations as well as special tests at the AFRL Starfire Optical Range.

 

The US Air Force will appreciate the contributions of Conrad Phillipi long after his name and our names are forgotten.  The term, “Rugate” invented by Conrad, to fit the optical design of his invention, may live forever.

 

A personal story.  Conrad retired about 1984 or 1985.  One of the research team members, Joe Davidson, who did early modeling using a remote terminal tied into the base computer system, Conrad Phillipi, Walter Johnson, and I went to lunch together; it was likely about 2010, so 25 years after Conrad retired.  Walt brought samples and final products of optical devices which had resulted from the early work, produced through several cycles of development process.  The devices included Laser Eye Protection Devices, sensor protection filters, and some prototypes of special filters that the team had done for Starfire Optical Range…, things not doable without the Rugate technology.  Conrad said little, but the smile seemed to be perfect and unerasable.

 

Returning to Conrad’s contributions as a research leader.  The team he inherited was a collection of folks with a very diverse background, many not schooled in optical materials.  Some were retrained, some passed and retired, but the team evolved - adding some of the most innovative people within the Materials Laboratory.  Many of these folks went on to become senior leaders within both the Materials Lab and AFRL headquarters.

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John Bagford (via Rob Hall):

Conrad was working in Bldg. 71A, with Charlie O, Don Stevison, Chuck Strecker, etc., in the original LHMEL, when I began working in August 1974. They all moved to Building 651 after Charlie and I set up the new lab, in the new building (what is now, the mushroom). While that move was going on, Doug Rabe and others built the first LHMEL I in 71-A. They turned the laser over to us in March 1976.

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Conrad always had snow-white hair and a distinguished mustache, drank tea out of a lab beaker, smoked a pipe and always worked, standing at his desk, no chair.

Sorry to hear of his passing. He was a good guy.

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Merrill Minges:

If you travel to Hawaii to tour the big space telescopes atop Mona Kea on the Big Island and Haleakala on Maui you will find that the astronomers there, from around the world, know about Conrad Fillippi’s rugate filters. Using these filters is very important in their work. On Haleakala there are Air Force space surveillance telescopes as well, so these astronomers have worked directly with Conrad.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

A set of mathematical tools has been developed for the optical design of very thin rugate films tailored so that specific wavelengths of light are reflected while still allowing the rest of the light to shine through. The mathematics of these design tools are well established but rather complex (inverse Fourier Transform analyses).

 

Conrad’s first important insight was that these analytical tools could be used to design a rugate filter which might solve an important AF problem which had just emerged: is there a way to reflect/reject a laser beam which could damage sensitive optical systems? At that time lasers were proliferating eventually becoming ubiquitous; they could be very small devices, but the beams could be very intense and damaging. 

 

Sunglass optics, for example, filter out lots of light but only let some through. So, the scene viewed would be somewhat dark. This simply won’t be acceptable for a pilot of a high-performance fighter or even for an airline pilot. The pilot must see everything bright and clear. If the laser energy rejection was very precise the view would be essentially unaffected.

 

In Conrad’s research group in ML dealing with laser threats had become immensely important so he set about applying the mathematical tools to design laser rejection optical films.

 

Conrad’s second important insight involved some serendipity. The technologies for depositing thin optical films had recently made major advances and these processes (e.g., chemical vapor deposition - CVD) were highly adaptable and controllable for depositing films of different chemical composition. Conrad understood that the challenge was adapting these processes to produce sharp laser rejection features necessary for AF applications.  The mathematical recipe showed that the necessary chemical composition profile across the optical film was very complex. Literally hundreds of wiggles or wrinkles were required. Furthermore, these wrinkles had to be very thin, a few atoms thick, and very precise.

 

Conrad was in the right place at the right time. The Air Force manufacturing program (MT) offices were located in ML. Conrad could simply walk down the hall to consult these manufacturing experts. This partnership was successful and within a relatively short time several small companies, under contract with Conrad and MT, were able to produce practical and economical rugate filters. 

 

 

 

 

 

        

                                                                            

                                                                                

 

 

 

 

 

It is quite amazing to see the very complex commercial machinery in operation producing rugate filters. Directed by the mathematical recipe, these machines automatically deposit many precisely controlled layers of different composition in a continuous manner. The change in chemical composition and therefore the change in optical properties of each layer can be adjusted real-time without interrupting the delicate deposition process.  The final product is an optical film, much thinner overall than a Saran Wrap sheet which has hundreds of unique layers. It was even possible to fabricate multiple filters in a single rugate film so that laser beams of different frequency could be reflected simultaneously.  This was an extremely important feature because ‘threat’ lasers might operate at several different wavelengths.

 

Conrad’s team set about adding these protective filters to many different types of Air Force optical equipment. Protection of the human eye was an especially important applications arena. Rugate films were successfully applied to combat fighter pilot helmets. Commercial airlines were able to quickly adapt the technology for use by their pilots. ‘Laser hardening’ of optical devices with rugate films was also adopted by the other services. They were especially important for the Army which had many different types of optical systems deployed in the field.

And it is clear why astronomers worldwide used rugate filters. They could quickly design and build optical (and infra-red) rugate filters so that specific wavelength regions of the light from distant space objects could be viewed unencumbered by unwanted light.

 

Conrad’s contributions were more than his key insights. He was dedicated and focused on bringing all the pieces together so that the Air Force had practical cost-effective solutions available to protect against a whole range of threats posed by lasers. Over time AF use of rugate filters in critically important applications became wide-spread -  his contributions were extraordinary. It was a pleasure to have known and worked with him – a very pleasant, low key AF innovator and leader.

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