Polarization effects in lasers and spectroscopy

Abstract

This special issue includes a wide range of papers contributed by the participants in the International Workshop on Polarization Effects in Lasers and Spectroscopy, held at the University of Toronto in June 1997. Participants were not restricted to manuscripts reporting the work they presented, rather they were invited to present new and current research activities they might wish to report that fell within the topics of the meeting. In addition, some manuscripts in this special issue are more tutorial or review in nature at our request; these are for the most part from the invited speakers at the conference or from the lecturers at the graduate-level two-day school held prior to the Workshop. The effects of polarization of the electromagnetic field and its interaction with magnetic sublevels of material systems are, of course, fundamental to a practical understanding of almost all field - matter interactions. However, what has now become conventional training in laser physics, and in quantum mechanics more generally, has often restricted the theoretical analyses to `two-level' systems and scalar fields for simplicity, to such an extent that the intuition of many working in both laser dynamics and spectroscopy is often less sensitive to subtleties of polarization of either the material or the fields. This workshop was organized to re-emphasize the importance of the states of polarization of both the material and the field, to illustrate the current activities which take advantage of these phenomena and to bring together several otherwise disconnected topics. The history of polarization effects in lasers and spectroscopy is a venerable one. Well developed schools of thought are embodied in the work of van Haeringen and de Lang [ 1 ] and Sargent and coworkers [ 2 ] in the 1960s and texts and review articles of Professor Voitovich and his colleagues in Minsk, Belarus [ 3 ]. Much of the early work showed the importance of polarization-sensitive spectroscopy in atomic gases as laser media. As applications of lasers required more intense sources, laser science turned to dyes and solid state lasers, in which many polarization phenomena observed in atomic gas lasers seemed absent. However, polarization phenomena are important today in the dynamics of nonplanar ring lasers, fibre lasers, microchip lasers and vertical cavity surface-emitting, semiconductor lasers, as emphasized by various manuscripts in this special issue. It is also worth noting that when interest in nonlinear dyanamics (optical bistability and optical instabilities) in field-atom interactions was revived in the 1980s, polarization-selective optical pumping techniques were required to create the experimental analogue of the two-level atom so popular for theoretical analyses. Furthermore the principles of laser-based trapping and cooling of atoms which merited the recent award of the Nobel Prize in physics would not be realizable experimentally without the subtleties of the interaction of polarized light and transitions among magnetic sublevels, which find their roots in Kastler's work on optical pumping [ 4 ]. Polarization degrees of freedom in the electromagnetic field also bring new `channels' for noise to enter dynamical systems and new opportunities for studying coupled modes or the effects of classical and quantum noise including correlations at various orders. The range of spectroscopic interests is illustrated by the early work of Hänsch and coworkers [ 5 ] and is standard fare in textbooks of chemistry and physics on spectroscopic methods. The importance of considering polarization continues through modern studies of such phenomena as dark resonances and coherent population trapping [ 6 ], lasing without inversion [ 7 ] and electromagnetically induced transparency [ 8 ]. Polarization is also of importance in the consideration of fast processes in solids, which can be resolved by ultrashort optical pulses [ 9 ]. The range of interest in polarization-sensitive dynamics spans the parity nonconserving decays in nucleii and atoms and the advantages of polarized electromagnetic waves for subtle probings of materials [ 10 ]. We are grateful for the response of participants in the conference and school, and are appreciative of the support of the members of the organizing committee (N B Abraham, USA (co-chair); M A Gubin, Russia ; S Haroche, France ; A Klehr, Germany ; L A Lugiato, Italy ; A D May, Canada (local co-ordinator); R A Morgan, USA ; K Otsuka, Japan ; W J Sandle, New Zealand ; G M Stephan, France (co-chair); L Svirina, Belarus ; C Tang, USA ; R Vilaseca, Spain ; J P Woerdman, The Netherlands ; N I Zheludev, UK ). We are also grateful for the support and encouragement of the honorary editor of Quantum Semiclass. Opt. , Professor P Mandel, the editorial staff of the Journals of the European Optical Society and of the publisher, IOP Publishing, for their patience and persistence in bringing this larger-than-usual special issue to fruition. We look forward to a continued expansion of work in this field which will be illustrated in the next conference on Polarization Effects in Lasers and Spectroscopy to be held at the University of Southhampton, UK just before the IQEC/Euro-CLEO in September 2000. The local organizer will be Dr N I Zheludev (E-mail: n.i.zheludev@soton.ac.uk; websites: http://www.nonlinear-optics.phys.soton.ac.uk/ and PELS conference website: http://www.phys.soton.ac.uk/PELS/INDEX.HTM ). We would like to particularly acknowledge the scientific inspiration that we have drawn personally from our colleague A D May and to express our gratitude for his boundless energy and tireless organizational skills that brought the meeting at the University of Toronto to such a successful conclusion. The help of our sponsors is also gratefully acknowledged, particularly the Embassade de France au Canada, the University of Toronto, and the French organizations region de Bretagne and departement des Cotes d'Armor. Other sponsors included JDS Fitel Inc (Canada), John Wiley and Sons, the Universitat Politecnica de Catalunya, Bryn Mawr College, and the Université de Rennes (Lannion). We are also grateful for the co-sponsorship of the following cooperating societies: European Optical Society, Quantum Electronics Divsion of the European Physical Society, American Physical Society and Optical Society of America. As a final note, we call to the attention of the readers of this special issue that three other manuscripts accepted too late for inclusion in this issue will appear in later issues of Quantum and Semiclassical Optics : Polarization of radiation amplified by dye solutions A Chernayavsky, L G Pikulik, K I Rudik and A F Grib Competition of active medium and empty cavity anisotropies in a single-mode gas class-A laser L Svirina Intensity and intermode beat frequency fluctuations in a two-mode He - Ne laser with synchronized modes N V Naumov, V N Petrovskiy, E D Protsenko and V M Yermachenko . 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B 13 no 6 [10] Schutz G and Fischer P 1996 X-ray circular magnetic dichroism Europhys. News 27 101 Guest Editors N B Abraham Department of Physics, Bryn Mawr College, 101 N Merion Ave, Bryn Mawr, PA, 19010-2899, USA G M Stephan ENSSAT, 6 Rue de Kérampont, Lannion, France