The LEOS Distinguished Lecturer Awards are presented to honor interesting speakers who have made significant contributions to the field of lasers and electro-optics. The program is designed to honor excellent speakers who have made technical contributions of high quality and to enhance the programs of the LEOS Chapters. Consideration is given to having a balance of speakers who can address a wide range of topics of current interest in the fields covered by LEOS. LEOS presents up to eight Distinguished Lecturer Awards annually.
The LEOS Distinguished Lecturer Awards program has been successful program for many years, and LEOS is proud to present profiles of the 2005-2006 recipients.

Sergio D. Cova

It was an honor to be selected as LEOS Distinguished Lecturer for 2005-2006. Receiving the news was great, but the real pleasure has been to discover how rewarding it is to visit various LEOS chapters and research groups, to share my research experience and findings and to have a stimulating exchange of views, opinions and expectations. I was worrying that a lecture on “Photon Counting Microdetectors and their Applications” might look quite specialized and not appealing to many people, but it turned out to be quite the opposite and I was impressed by the broad interest denoted by the number of invitations arriving from sites all over the world. Many of them were far away and implied long distance travels: I had to define a plan of lectures on one hand compatible with my teaching duties and on the other able to satisfy various requests and minimize the travel costs. This has been possible thanks to the very collaborative attitude that I met everywhere and to the great assistance that I had from my friend Nick Bertone of Optoelectronic Components for taking contacts and defining schedules.
The first lecture was on October 27, 2005 at the LEOS Scottish Chapter. I was invited in May from the Chapter Chair Catrina Bryce, University of Glasgow, but the lecture was given at Heriot Watt University in Edinburgh as Ajoy Kar had taken over as Chapter Chair. The session was chaired by Gerald Buller as representative of the Chapter Chair, who attended the LEOS Annual Meeting in Sydney. It was indeed a good start: at HWU there is intense research activity on photon counting, the audience was very interested and active and Gerald is a good friend!
I managed to have a couple of weeks free in January 2006 for a tour in the US and Canada, committed to a set of lectures. On January 16 Monday evening I gave a lecture to the Boston Chapter. I was cordially welcomed by the Chair Matt Emsley and other chapter members and it was interesting to visit the old GTE research labs where the chapter meeting was located. There was a wide attendance of people coming from research laboratories and high-tech companies of the Boston area and this naturally brought stimulating discussions and exchange of views and opinions. The next lecture was scheduled on January 18 evening at the Northern Virginia chapter in Maryland University, College Park, very efficiently coordinated by Lucy Zheng. I traveled by air and by car with Nick Bertone and we had the opportunity to visit also the NIST laboratories at Gaithersburg and NASA Goddard Space Flight Center where I had stimulating interactions with researchers interested in photon counting. At Maryland University the attendance was remarkably wide and I was impressed by the enthusiasm and the attention dedicated to my lecture. The next lecture was scheduled on January 19 at the Hampton Roads chapter in Norfolk, VA. We traveled by car and I enjoyed the green landscape of South Eastern Virginia, where Spring appeared to be much nearer than it was in the Boston area. At Old Dominion University we were warmly welcomed by the Chapter Chair, Prof. Amin Dharamsi, who gave us a wonderful tour of the campus. With respect to the previous talks the audience was remarkably different, composed by EE students of the university. They followed with attention and interest and set not only naïve queries, but also some penetrating and insightful questions. It was very interesting to compare this experience with students to that made in Italy. We traveled then by air from Norfolk to Albany and by car from Albany to Canada for the next lecture, agreed by kind invitation of Kexing Liu, Chair of the Ottawa chapter. The lecture was given on January 20 at the National Research Council, as invited contribution to the IEEE-LEOS, OPRA, NRC (IMS) 2nd Workshop on “Recent Advancements in Photonics”, chaired by Ruth Rayman of OPRA. It was a nice and well focused meeting and I enjoyed being there and listening to the other speakers. I had also a wonderful tour of the NRC facilities for the fabrication of III-V semiconductor devices. I admired the concrete support that the Canadian government has been able to give to technological research, much better indeed than what I have seen in European countries in general and in my country in particular. We travelled then to California and in the weekend I had the opportunity of attending part of the SPIE Bios conference in S. José. On January 23 Monday I gave my last lecture of the tour at the Sacramento LEOS Chapter. I was welcomed at the UC Davis campus by the Chair S. K. Ramesh and other chapter members. It was a special session with two LEOS Distinguished Lecturers, which offered to the audience an interesting mix of scientific and technical themes and gave to me the opportunity to listen to the lecture of David Plant. I appreciated the attention and interest that the audience showed for the broad range of topics illustrated by the speakers. This lecture was the last lecture of the tour and I traveled then back to Milano. A note on travel issues: I had thought that in January complications to the travel by car from the US to Canada could arise from heavy snowfall, but this didn’t happen. What happened was a heavy snowfall in Milano just at the time I was getting back: Milano airports were closed and I was left stuck at London airport one full day!
In May 2006 I will make another tour at various chapters in the US and I will give my lecture to the LEOS Italy chapter. I will be able in the future to satisfy various other requests that arrived to me from LEOS chapters. In fact, my term has been extended to 2006-2007 and this will give me the opportunity of continuing this pleasant and stimulating experience.
Sergio Cova is full professor of Electronics since 1977 at Politecnico di Milano (Italy), where he had received a doctor degree in Nuclear Engineering in 1962. He worked then as post-doc, assistant and associate professor at Milano and University of Parma (Italy) and in 1976 he was appointed full professor at University of Bari (Italy). He is a Life Fellow of the IEEE and coauthor of over 180 papers in international journals and conferences and of 5 US and European patents. His research contributions are mainly on detectors for optical and ionizing radiations, on microelectronic devices and circuits, on electronic and optoelectronic measurement instrumentation. In collaboration with researchers in other fields (physics, astronomy, biochemistry and molecular biology) he carried out also interdisciplinary work and devised new dedicated techniques and devices.
He has given extensive contributions to the introduction and development of single-photon counting techniques, first with PhotoMultiplier Tubes (PMT) and then with solid-state detectors. He pioneered the development of Single-Photon Avalanche Diodes (SPAD), inventing in 1975 the active-quenching circuit (AQC), which opened the way to their application. He has been leading a research group where various generations of brilliant young scientists grew up working on SPADs and related matters. The group developed AQCs in successive generations and in 1995 was the first one to implement them in monolithic integrated form, thus making possible miniaturized photon counting instrumentation and complete photon-counting modules on a chip. The group developed in successive generations new planar epitaxial silicon SPAD devices with picosecond photon-timing capability, developing CMOS compatible technologies and working in collaboration with various silicon foundries in industry and academy. From 1992 the group pioneered the extension of single-photon techniques to the infrared spectral range with Germanium and InGaAs/InP avalanche diodes. The group contributed to diversified applications of photon-counting detectors, such as: fluorescence measurements for DNA and protein analysis and single-molecule studies; characterization of optical fibers and lasers; adaptive optics systems in telescopes; non-invasive testing of ULSI circuits; and others.
In 2005 S. Cova with some colleagues established the Politecnico di Milano spin-off company “Micro-Photon-Devices” MPD for producing and making widely available to experimenters the photon counting micro-detectors developed in their research.

Summary of lecture:
Photon Counting Microdetectors and their Applications
Photon counting is the technique of choice for attaining the ultimate sensitivity in measurements of optical signals. This occurs essentially because it is completely digital, starting from the photodetector, and therefore completely avoids the limitations set by the noise of electronic circuits in the analogue measurements of light, which are carried out by measuring the output current signals of photodetectors. It requires, however, photodetectors with an internal amplification mechanism that generates in response to single optical photons macroscopic electrical signals, with amplitude well above the level of noise in circuits. Photon counting was introduced and developed with photomultiplier tubes, but it received new impulse from the introduction of microelectronic detectors, called Single-Photon Avalanche Diodes SPAD. This device exploits the avalanche phenomenon in a junction not for linear amplification as ordinary Avalanche PhotoDiodes (APD) do, but instead with an approach conceptually similar to that of Geiger-Mueller counters of ionizing radiation. SPADs thus produce in response to a single photon a standard current pulse with macroscopic (milliampere) size and fast (subnanosecond) rise, which marks the arrival time of the photon. Besides the general advantages of semiconductor devices versus vacuum tube devices, such as reduced size and cost, higher reliability, ruggedness, suitability to integrated systems, SPADs offer remarkably improved basic performance in terms of higher photon detection efficiency, lower dark-counting rate and higher resolution in photon-timing, capability of efficient operation up to very high photon counting rate. The lecture outlines the evolution of the SPAD devices and of the associated electronics and points out the physical phenomena that underlay the detector operation. It illustrates significant examples of recent applications of SPAD detectors, from the analysis of DNA and proteins to studies of single molecules to adaptive optics systems in modern telescopes to non-invasive testing of ULSI circuits. It finally discusses the prospect of further progress in this field.

Bishnu P. Pal

Circa April 2005 I was pleasantly surprised to learn through a congratulatory email from my old pal from our Graduate study days at IIT Delhi namely, Dr. Ram Gopal Gupta, who chairs the India LEOS chapter about my selection as DL. I consider it to be a privilege and great honor for being bestowed this title by a great professional society like IEEE/LEOS and also for having been chosen for this honor for the first time from India. I was flattered by the sheer number of invitations from various LEOS chapters around the world that followed. As I had a deadline at hand to meet during the summer of 2005 to complete proof checking and editing of my recent book entitled Guided Wave Optical Components and Devices: Basics, Technology, and Applications (Academic Press/Elsevier, 2006) I had to postpone my first visit as a DL till fall of 2005. My first visit took place in September to the Crimean city Yalta at the invitation of Ukraine LEOS chapter chair Prof. Igor Sukhoivanov, who organized a special 1-hour DL session for my talk during the IEEE/LEOS conference on Advanced Optoelectronics and Lasers (CAOL). At the conference I had the pleasure of also meeting LEOS Vice President Dr. J. Buus (a report on CAOL has appeared in the February 2006 issue of this newsletter). Interestingly it turned out during one of the dinner table discussion that both he and I had participated at the first round robin fiber measurement (in which the same fiber was sent around four different identified laboratories in the four Scandinavian countries for its characterization under well defined identical experimental condition) meeting organized by Nordforsk (Nordic Science Council) way back in 1976 at Sigtuna near Stockholm. I had gone there as a member of the Norwegian measurement team from the then Norwegian Institute of Technology at Trondheim, where my responsibility involved refractive index profiling of optical fibers as a Royal Norwegian CSIR Post Doctoral Fellow. Prof. Sukhoivanov and his team from Kharkiv National University of Radio Electronics, who organized the conference, were very pleasant as hosts and the conference was quite a success. I had opportunity to meet several scientists from that part of the world. One of their Ukrainian national TV channels also interviewed me about the conference on the last day of the conference through an interpreter. On way to Ukraine I had stopped by at Moscow for three days for delivering a seminar and also for technical interactions at the Fiber Optics Research Center (FORC) located within the General Physics Institute (GPI) of the Russian Academy of Sciences, who collaborates with us on Bragg fibers. GPI is an incredible institute as it boasts of having produced 7 Noble Laureates in Physics!
My next DL talk was at the LEOS India chapter in Calcutta on January 3, 2006 organized by Prof. P.K. Basu jointly with a DL talk of IEEE/EDS delivered by Prof. H. Iwai from Tokyo Institute of Technology. It was organized one day before the international conference on Electronics and Photonic Materials, Devices, and Systems (EPMDS), which took place in Calcutta (now known as Kolkata). Many students from the Institute of Radio Physics and also from the Department of Electronic Science of Calcutta University attended it. I was happy to find keen interest shown by some students after the talk. The local chapter office bearers also treated Prof. Iwai and me to a sumptuous dinner at a Chinese restaurant.
In February this year we had a short teaching break of three days and I used this opportunity to honor invitations from the LEOS chapters from Singapore and Korea. The talk at Singapore was held on February 6th at the EE Department of Nanyang Technological (NTU); my hosts were Prof. Perry Shum Ping, Director of the Network Technology Research Center and Prof. Sheel Aditya of the EE Department. It was great to see that the lecture theater was full with several faculty and many students. The animated discussions that took place with the bunch of enthusiastic students before and after the talk were very stimulating. I also met few of our past students from my Institute, who are either pursuing graduate studies or are serving different research centers as members of the technical staff. There after I moved to Seoul (Korea) where Prof. Namkyoo Park and Prof. Byoungho Lee of the Korean National University organized a seminar on February 8th at the EE Department and on 9th I had the privilege of delivering my DL talk as a plenary talk at the annual meeting of the Korean Optical Society. My talk was followed by another plenary talk by Prof. Peter Delfyett from CREOL, Florida. It was a well-organized meeting with poster sessions as well as a technical exhibition. It was my first visit to Korea, which I greatly enjoyed and also meeting several outstanding researchers and graduate students was a bonus. It was a pleasure to meet LEOS (Korea) chapter chair Professor El-Hang Lee, who was very appreciative of my talk. So far out of the 17 invitations that I have received I could honor only the above-mentioned four and I intend to cover a large number in the US during May-June 2006 summer vacation time. I have been already informed by the LEOS Secretariat about my extended DL term till June 30 2007 and I am eagerly looking forward to visiting as many LEOS chapters in different countries till June next year. As a LEOS DL it has indeed been a great opportunity to exchange views/scientific ideas with so many research scientists and research students around the world and I doff my cap to the LEOS Board of Directors for having created and established this Distinguished Lecturers program and I also to record my appreciation of the staff, who manages this program at the LEOS Secretariat at Piscataway, New Jersey.
Bishnu P. Pal was born in Shillong, India on 3rd December 1948. He received M.Sc. and Ph.D. degrees in Physics from Jadavpur University and IIT Delhi in 1970 and 1975, respectively. He has worked as Visiting Scholar/Visiting Professor in the area of Fiber Optics and Applications for various periods at the Norwegian Institute of Technology (Trondheim, Norway), the Fraunhofer Institute für Physikalische Messtechnik (Freiburg, Germany), the National Institute of Standards and Technology (Boulder, CO, USA), University of Strathclyde (Glasgow, UK), City University Hong Kong, and Universities at Nice and Limoges (France). In late 1977 he joined the academic staff of IIT Delhi, where he is a Professor of Physics since 1990. He had been a member of the founding Editorial Advisory Board of the International Journal of Optoelectronics (1988-93) published by Taylor and Francis from UK and is currently a Member of the Editorial Board of Optoelectronics Letters (China) and IETE (India) Journal for Students. He Guest Edited special issues of Journal of Optics (India) devoted to Guided Wave Optical Components and Devices (2004), Proc. IEE (Optoelectronics) devoted to Guided Wave Optics on Silicon (1996), International Journal of Optoelectronics devoted to Optoelectronics in India (1993) and Joint issue of JIETE and IETE Tech Review devoted to Optoelectronics and Optical Communication (1986). Prof. Pal has extensive teaching, research, sponsored R&D, and consulting (for Indian and US industries) experience on various aspects of Fiber Optics and he has published and reported over 100 research papers and research reviews in peer reviewed international journals and conferences. He is co-author of the book entitled Fiber Optics and Instrumentation (in Russian, Mashinostroenie Publishing House, Leningrad, 1987) and has edited the books: Fundamentals of Fiber Optics in Telecommunication and Sensor Systems (Wiley Eastern, New Delhi and John Wiley, New York, 1992, 3rd reprint 2001) and Guided wave Optical Components and Devices (Academic/ Elsevier, Burlington, 2006). He has also contributed by invitation 12 chapters in books. Prof. Pal is a Fellow of Optical Society of India and IETE and is a Member of the Optical Society of America and IEEE/LEOS. He has been an invited speaker at over 20 international conferences held in India and abroad. He is a co-recipient of the First Fiber Optic Person of the Year award in 1997 instituted by Lucent Technology in India and also the Gowri Memorial Award for the year 1991 of IETE. Prof. Pal is currently a member of the Executive Council of the Optical Society of India and he has been chairperson of the National Technical Panel on All-fiber Components for the Department of Information Technology of the Indian Government. His current research interests concern all-fiber components for DWDM and optical networks, dispersion compensators, photonic bandgap fibers, and fiber optic sensors for civil engineering structures.

Summary of lecture:
Photonic Bandgap Bragg Fibers: A New Platform for Realizing application- specific Specialty Optical Fibers and Components
Consequent to the mind boggling progress in high-speed optical telecommunication witnessed in late 1990s, it appeared for a while that it would only be a matter of time before the huge theoretical bandwidth of 53 THz, offered by low-loss transmission windows (extending from 1280 nm to 1650 nm) in low water peak high-silica optical fibers would be tapped for telecommunication through dense wavelength division multiplexing techniques! In spite of this possibility, in recent years there has been a considerable resurgence of interest amongst researchers to develop application-specific specialty fibers. Research targeted at such fiber designs in the early 1990s gave rise to a new class of fibers, known as Photonic Crystal Fibers (PCF), characterized with wavelength scale periodic refractive index features. These structures were found to exhibit photonic bandgaps, which is a consequence of a periodic distribution of refractive index in a PCF. However by introducing a defect region in an otherwise periodic structure, light (within the bandgap) could be localized in the defect region thereby mimicking a fiber core. The defect region could be a medium of refractive index lower (e.g. air) than the surrounding also. Such PCF’s are known as photonic bandgap (PBG) fibers. Bragg fiber is an example of an 1D-PBGF, and because of a multitude of physical parameters that could be altered independently, their propagation characteristics can be tuned relatively with ease to control and maneuver light guidance for a variety of applications, ranging from telecommunication to sensors. The Bragg fibers can also be formed around silica core through the route of well-known MCVD process of fiber manufacture. By configuring a dispersion managed Bragg fiber one could alternatively enhance nonlinear optical effects in it and exploit the same to achieve for example, supercontinuum generation in such structures. In this talk our focus will be to highlight the basic functional principle of propagation in Bragg fibers, modeling methods implemented by us, and realization of few attractive designs of several application specific Bragg fibers like dispersion compensating fibers of ultra-high figure of merit and transmission fibers for metro networks as well as all-fiber components potentially feasible around this technology platform e.g. supercontinuum generator for applications in optical coherence tomography in the near-infrared wavelength region .

David V. Plant

It has been an honor and pleasure to serve as a LEOS Distinguished Lecturer for 2005 – 2006, and I am looking forward to continuing during my extended term in 2006 – 2007. I have had the pleasure of visiting several LEOS chapters throughout Canada and the United States.
My first stop was to the Sacramento LEOS chapter where I was warmly greeted by Professor S.K. Ramesh. This visit was particularly eventful because Professor Ramesh was able to coordinate two distinguished lectures on the same evening, the second one being given by Professor Servio Cova.
I greatly enjoyed visiting the Toronto LEOS Chapter through the invitation Dr. Emanuel Istrate. While in Toronto I had the pleasure of visiting a number of researchers and their laboratories at the University of Toronto where I learned a great deal about ongoing research in photonics and microwaves.
I was thrilled to visit the Washington/Northern VA LEOS chapter where my visit was coordinated by Dr. Lucy Zheng and Dr. George Simonis. Having never been to the University of Maryland at College Park, I was excited to visit the campus. In addition, it was enjoyable catching up with George who I have known for many years.
My “home” lecture was to the Montreal LEOS chapter where my visit was coordinated by Dr. Peter Noutsios, Professor Lawrence Chen, and Professor Ke Wu. The Montreal LEOS Chapter is particularly active given the large number of students and high-tech companies located in the city.
One highlight of my travels was the opportunity to give a talk at the Dallas LEOS chapter where my visit was coordinated by a long time friend Professor Duncan MacFarlane. Duncan and I went to school together but had not seen each other for some time and so we enjoyed getting “caught-up”. I am also grateful to Duncan for arranging visits to local companies while in the area.
During the remainder of this term and my second term I am excited about the visits I have planned which include stops at Queen’s University, the Ottawa Chapter, the Central New England/ Boston Chapter, the Orlando Chapter, the Hampton Roads/Norfolk Virginia Chapter, the Rochester Chapter, and the San Diego Chapter. In addition, I am looking forward to visiting the Benelux Chapter in December 2006 to participate in the Annual Symposium of LEOS which is held every year, as well as visiting the St Petersburg, Russia chapter in connection with Optoinformatics/ IP2006 which will be held in Sept. 2006.
Once again I would like to express my gratitude to LEOS and the LEOS Chapters for the opportunity to participate in this program. Everyone involved is extremely dedicated to the program which is certainly reflected in the successes achieved.

Summary of Lecture:
Agile All-Photonic Networks
Abstract: Recent advances in fiber optic technology have prompted researchers to envision a future all-photonic network that is capable of supporting multiple access and services at very high bit rates. The confluence of optical transmission and optical network functions opens up new paradigms for network architectures that are enabled by emerging photonic technologies. Characteristics of these architectures and technologies that distinguish them from existing ones include: (1) networks in which the transmission of information is based on optical packets (burst-switched or packet-switched networks, with and without all-optical header recognition), (2) optical code-division multiplexing for allocating bandwidth-on-demand in bursty, asynchronous traffic environments, and (3) practical implementations for optical generation, shaping, and processing. The bursty nature of these networks imposes new design constraints on transmitters, receivers, and optical components. We review various system and technology considerations for such networks.
David V. Plant received the Ph.D. degree in electrical engineering from Brown University, Providence, RI, in 1989. From 1989 to 1993, he was a Research Engineer at UCLA. He has been a Professor and Member of the Photonic Systems Group, the Department of Electrical and Computer Engineering, McGill University, Montreal, QC, Canada, since 1993, and the Associate Dean – Research and Graduate Education since 2006. He is the Director and Principal Investigator of the Centre for Advanced Systems and Technologies Communications at McGill University (www.sytacom. mcgill.ca). He is also Scientific Director and Principal Investigator of the Agile All-Photonics Networks Research Network (www.aapn. mcgill.ca). Dr. Plant currently serves as the Editor of the LEOS Web Portal and as a Topical Editor of the OSA’s Applied Optics, and he has served as an Associate Editor of the LEOS Newsletter in 2004 and 2005. He is a member of numerous technical program committees, including the LEOS Annual Meeting (Local Arrangements Chair for 2006), the LEOS Workshop on Interconnections within High-Speed Digital Systems, and the OSA Annual Meeting.
His research interests include optoelectronic-VLSI, analog circuits for communications, electro-optic switching devices, and optical network design including OCDMA, radio-over-fiber, and agile packet switched networks. He has authored or coauthored over 185 refereed journal publications and conference papers, one book chapter, and one patent. Dr. Plant has received numerous awards from McGill, most recently and the Carrie M. Derick Award for Graduate Research Supervision and Teaching in 2004, and the Samuel and Ida Fromson Award for Outstanding Teaching in 2006. He was named an inaugural James McGill Professor in 2001, an IEEE Distinguished Lecturer for 2005-07, a Fellow of the Optical Society of America in 2006, and is the recipient of the 2006 R.A. Fessenden Medal from IEEE Canada. He is also a Senior Member of the IEEE and a member of Sigma Xi.

M. Selim Unlu

He has visited and given talks at the following Chapters: September 2005, Hampton Roads Chapter, invited by Prof. Amin Dharamsi; October 2005, Ottawa, Montreal, and Central New England Chapters, invited by Drs. John Bernard, Peter Noutsios, and Matthew Emsley; December 2005, Washington/N. VA Chapter, hosted by Dr. Lucy Zheng; February 2006, Ft. Worth, TX and Northern NJ Chapters, hosted by Professors Weidong Zhou and Haim Grebel.
M. Selim Ünlü is a Professor of Electrical and Computer Engineering, Biomedical Engineering, and Physics at Boston University. Prof. Ünlü received the B.S. degree in electrical engineering from Middle East Technical University, Ankara, Turkey, in 1986, and the M.S.E.E. and Ph.D. in electrical engineering from the University of Illinois, Urbana-Champaign, in 1988 and 1992, respectively. In 1992, he joined the Department of Electrical and Computer Engineering, Boston University.
Dr. Ünlü’s career interest is in research and development of photonic materials, devices and systems focusing on the design, processing, characterization, and modeling of semiconductor optoelectronic devices, especially photodetectors, as well as high-resolution microscopy and spectroscopy of semiconductor and biological materials.
During 1994-1995, Dr. Ünlü served as the Chair of IEEE Laser and Electro-Optics Society, Boston Chapter, winning the LEOS Chapter-of-the-Year Award. He was awarded National Science Foundation Research Initiation Award in 1993, United Nations TOKTEN award in 1995 and 1996, and both the National Science Foundation CAREER and Office of Naval Research Young Investigator Awards in 1996. He has authored and co-authored over 200 technical articles and several book chapters and magazine articles; edited one book; and holds several patents. His professional service includes the former chair of the IEEE/LEOS technical committee on photodetectors and imaging and currently, the current chair of IEEE/LEOS Nanophotonics committee. He is also serving as an Associate Editor for IEEE Journal of Quantum Electronics and a VP of LEOS.

Summary of lecture:
Nanoscale Imaging of Semiconductor and Biological Systems
We present two innovative approaches to go beyond the capabilities of standard optical microscopy which is limited to a transverse resolution of approximately half a wavelength due to the diffraction, also termed the Rayleigh or Abbe limit. The resolution is inversely proportional to the Numerical Aperture (NA). One method to increase the NA is to increase n, the refractive index of the material in the object space. We recently developed a new technique involving a Numerical Aperture Increasing Lens (NAIL) for diffraction limited subsurface microscopy. The NAIL technique is demonstrated by near-IR inspection of Si integrated circuits yielding a 230 nm resolution at 1050 nm wavelength representing a factor of 4 improvement over the state-of-the-art. We have applied this technique to photoluminescence and PLE measurements of InAs/GaAs quantum dots and demonstrated high collection efficiency and spatial resolution better than 400 nm. We also used NAIL technique in subsurface thermal emission microscopy of Si integrated circuits and achieved improvements in the amount of light collected and the spatial resolution, well beyond the limits of conventional thermal emission microscopy. We experimentally demonstrate a lateral spatial resolution of 1.4 µm and a longitudinal spatial resolution of 7.4 µm, for thermal imaging at free space wavelengths up to 5 µm. We also examine in detail the ability of sharp metal tips to enhance local optical fields and describe a new approach to nano-optics, that of combining solid immersion microscopy with tip-enhanced focusing and show how such an approach may lead to 20 nm resolution with near-unity throughput.
Spatial resolution can also be improved beyond the diffraction limit by collecting spectral information. We have built on our experience on resonant optoelectronic devices and developed a novel application to fluorescence microscopy that promises nanometer resolution in biological imaging. Over the past 20 years fluorescence microscopy has developed into a standard tool in biological sciences. Today, confocal microscopy provides three-dimensional resolution on lateral length scales of 0.5 micron and axial length scales of 0.75 micron with good imaging speed for studies of biological systems. In the past few years, the increased resolution achieved through advanced fluorescent probes and two-photon sources has made possible the coarse examination of structures at the subcellular level, complementing decades of molecular biology with the nascent ability to localize subcellular processes. We have developed an alternative method, spectral self-interference fluorescent microscopy. The technique transforms the variation in emission intensity for different path lengths used in fluorescence interferometry to a variation in the intensity for different wavelengths in emission, encoding the high-resolution information in the emission spectrum. Using monolayers of streptavidin, we have demonstrated better than 5nm axial height determination for thin layers of fluorophores and built successful models that accurately fit the data. Initial experiments on fluorescently labeled lipid layers successfully determined the binding of fluorescent molecules in membranes with sub-nanometer precision. Recently, the orientation of ss and dsDNA monolayers on silicon oxide is studied by tracing the location of a fluorescent label attached to the DNA.

MARCUS K. WELDON
Information not available at time of print.