CLEO '86—IQEC '86

broad coverage of the current understanding of optical instabilities through a series of tutorial reviews and to offer a representative selection of present research activities in this area. As such the book is valuable both to workers currently active in this field and to anyone wishing to make a first acquaintance with the subject.

pages length, and divided into seven areas. These are: (I) Instabilities in Single-Mode Lasers, (II) Instabilities in Multimode Lasers, (III Lasers Containing Saturable Absorbers, (IV) Lasers wi s’h External Perturbation, (V) Instabilities in Bistable Optical Systems, (VI) Instabilities in Nonlinear IOptical Systems, (VII) Effects of Noise.

Perhaps more laser users than realize it need to become acquainted with aspects of this subject since laser instabilities of a fundamental nature (that is, not arising from technical imperfections) are by no means all confined to contrived situations - they are quite readily induced under familiar operating conditions.

In the research contribution there is a roughly equal balance between theoretic 1 and experimental papers. In the tutorial reviews the e is a greater emphasis on theory. Overall however, t ere is a good balance between theory and expe d ment which suggests a good interaction between and experimentalist. This is a healthy sign and this ook should certainly contribute to a of this of this fruitful interaction.

Of the 396 pages that make up the book somewhat more than half is devoted to tutorial reviews (16 in all) ranging in length from 10 to 20 pages. This is followed by a collection of research contributions, each of three

D.C. Hanna

CONFERENCES CLEO ‘86 San Francisco,

IQEC ‘86

California,

USA, 9-l 3 June, 1986

This conference, probably the largest of all the laser conferences, was held in the Moscone Convention Centre in downtown San Francisco. The technical sessions comprised eight parallel sessions running from 8.30 am to about 5 pm each day which, together with three large poster paper sessions and several postdeadline paper sessions, contained more than 750 papers in 138 sessions. In such a comprehensive programme there was naturally a very wide range of topics to cover all aspects of lasers developments, laser applications and laser related physics. Areas which were noted for their large and expanding contributions were: picosecond and sub-picosecond technology and applications (eight sessions), non-linear optics (21 sessions), semiconductor lasers and integrated optics (12 sessions), tibre-optics and optical communications (eight sessions), medical, chemical and biological applications (11 sessions). The development of sub-picosecond pulse sources is seeing major advances especially in the variety of techniques and wavelengths which access the region around 100 fs. With commercial systems now available offering tunability at pulses well below 1 ps there has been a rapidly growing community of groups using sub-picosecond sources for various applications notably in semiconductor physics, photochemistry and biology and in the new physics associated with high intensity multiphoton interactions with atoms. This latter work led to several papers from groups

VOL 18 NO 5 OCTOBER 1986

reporting on sub-picosecond lasers with very high power and irradiance: 50 GW sources giving focal intensities of 10” W cmvz were described by University of Chicago, University of Rochester and University of Tokyo, with the potential, using large aperture KrF or glass amplifiers, of powers greater than 10 TW and focal intensities as high as 102’ W cm-*. One of the most popular sessions described recent developments in x-ray lasers. Three groups (Lawrence Livermore Laboratory, Rutherford Laboratory and Princeton University) now report significant gain at wavelengths around 20 nm using schemes relying either on collisional pumping (Se) or recombination (C). Using two of the NOVA beams at the LLNL x-ray super-radiant powers of 1 MW were achieved with gain lengths of 4 cm. The output of 200 @ is within sight of extracting an appreciable fraction of the stored energy. Considerable success is also being achieved now with free electron lasers. Several practical devices are now in operation giving wavelengths from the visible to the far infra-red and microwave region. An impressive 30% efficiency has been achieved in the far infra-red by LLNL using a LINAC driven FEL. High efficiencies and high powers are much more difficult at shorter wavelengths and are still a long way off for visible devices. There is still considerable the gradual development

interest in laser fusion with of larger and more sophis-

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ticated laser systems and improvements in target irradiation uniformity. Three groups reported increased yields from fusion targets with measured energies in thermonuclear neutrons up to 25 J with an efficiency (laser to thermonuclear energy) of 0.1%. However it has proved very difficult to achieve the high fuel density of 200 g cu cm-’ to approach the Lawson criteria for significant bum. Current peak densities lie at definite 20 g cu cm-‘. There were detectable trends in the direction of development of laser systems. The last couple of years has seen a major interest in tunable solid state lasers and a number were reported at CLEO. For example the Ti: sapphire laser was reported to be tunable at room temperature from 700 to 1000 nm with high efficiency. This is very impressive in comparison with say ‘tunable’ dye lasers. Other tunable lasers reported were chromium doped garnets and Ti: YAG. The increasing interest in excimer lasers continues with a number of papers adding to the understanding of these systems and leading to improvements in spectral irradiance, repetition rate, pulse energy and lifetime. Many of the conference topics were covered in the ‘theory’ sessions. The current interest in quantum optics is in ‘squeezed states’ which suggest the possibility of reduced noise at well below the quantum noise limits, and hence attracts the attention of those working in optical communications. The conference showed a noticeable input from the SD1 programme even at this fairly early stage. Results of work funded by SD1 were reported in the following areas: excimer laser developments; Raman systems, phase conjugation and free electron lasers. We can

look forward to some significant areas over the next year.

advances

in these

The conference was complemented by a very large, well laid out and comprehensive exhibition with some 300 exhibitors from many countries. A galaxy of high tech equipment was on display to a value which was also astronomical. In particular evidence on the laser side were excimer lasers (one from Lambda Physik even played the German national anthem by continuously varying its repetition rate into an air spark - a good example of an all-singing-all-dancing laser perhaps !), picosecond laser systems and semiconductor lasers. The use of microprocessors are now much in evidence in many of the devices on sale to assist in control and data processing. Considering the size and scope of the conference and exhibition, the organisation was excellent with very few problems. However delegates found it impossible to do justice to what was on offer in the time available, even taking a personal view with specialized interests. It is certainly not possible to do it justice in a personal review. The conference welcomed delegates from a great many countries including an notable increase from the Republic of China and a large group from Japan who are very strong in the fields associated with semiconductor lasers and optical communications. With so many countries represented it was a particular disappointment to see so few from the USSR especially in fields in which its workers, having made notable contributions to those fields, were invited to give review papers. LN. Ross

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OPTICS AND LASER TECHNOLOGY