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Fourth national quantum electronics conference
The CO2 laser cannot yet be efficiently transmitted by fibre optics so it cannot be used in endoscopic or similar applications but only in 'open' surgery in accessible areas. The 'internal' use of lasers in applications such as endoscopy seems to me to be a very beneficial way of using lasers in the future; just like retinal welding much can be achieved without having to perform risky operations. There is also much less risk of stray laser light to endanger personnel during the operation. Apart from Carruth's paper on safety precautions and medico-legal aspects of laser use there were several other papers of interest. Dr. C.K.N. Patel described some general work with the CO2 laser and the state of the art in fibres for efficient CO2 laser transmission. He was confident that a 50-75% transmission fibre would be produced in the near future although fibre tip damage was still a great problem and the development of diamond capping to overcome this was described. It seems that only 25% of CO2 laser applications need a fibre - a mirror system can be used for the remainder. Two papers from Munich and Japan give interesting results from studies of laser radiation on tissue. It is difficult to perform controlled trials on these effects but some workers have attempted experiments on tissue and organs removed from animals which may give unreliable results due to the lack of blood flow in the samples. A paper from the USA discussed the possible applications of photacoustic spectroscopy in medicine. This technique is proving a useful tool in non-medical-applications and may well have great promise for the future but the crude results presented at the conference hardly demonstrated this. One of the best pieces of scientific work presented was by Dr. Saunders of Richmond, Virginia on the use of lasers in neurosurgery. He correlated morphological tissue changes with functional changes. The interest lay in the promise of being able to remove brain tumours sited close to vital nerves without damaging these nerves. The standard of presentation in the gastroenterology session was far superior to that in other sessions. This was probably due to the fact that the CO2 laser is not a candi-
date for the most exciting application, ie endoscopic photocoagulation and the chairmen were quick to shoot down the one or two dubious papers which did appear. The main speakers were R.M. Dwyer (USA) and P. Kiefhaber (FDR). Their considerable practical experience was apparent and both, especially Kiefhaber, had taken great pains to classify their successes and failures during several years experience with the Nd: YAG laser. An interesting paper of Konigsmann (FDR) discussed the relative cutting and hemostatic effects of CO2, CO and Nd: YAG lasers. His results showed that the CO2 laser is best for cutting tissue and the Nd:YAG laser is best for sealing blood vessels. Other speakers showed that the Nd: YAG is superior to the Argon laser for sealing large blood vessels. A general point noticed during the congress was the increasing participation of Japanese speakers and delegates over the first two congresses. One speaker from Japan revealed that several million pounds is being spent in his country to develop second generation medical laser systems by 1981. Since the next congress will be held in Tokyo in 1981 it is easy to see that it will be almost completely dominated by the Japanese who clearly see a large market for such equipment. A technical exhibition was held during the conference with most of the well established manufacturers present. It was no surprise to find a CO2 laser system in a prominent position. Many delegates had great fun performing laser surgery on oranges and similar items; the complete absence of any shielding to prevent stray laser light being scattered all over the place was rather alarming. Indeed one exhibitor had a hole burned in the curtain at the back of his booth after a laser was left running accidentally! On the whole then, an unsatisfactorily conference. There is a major role for lasers in medicine but it will be a few years before sufficient reliable information will be available to sort out the really useful applications from the gimmicks. The conference proceedings will be published. A.F. Purdie
Fourth national quantum electronics conference Edinburgh, UK, 19-21 September 1979
scientific contributions were augmented by twenty exhibits of commercial laser and optical equipment, and by a conference bookstall. The exhibition was interesting, of excellent quality, and in our view contributed significantly to the general value of the meeting.
The fourth in a biennial series of conferences organized by the quantum electronics group of the Institute of Physics was held at Herriot-Watt University (Riccarton Campus), Edinburgh, from 19-21 September 1979. The meeting was co-sponsored by the Chemical Society and the IEE. The resulting interdisciplinary nature of the proceedings attracted an audience of over 200. Following a pattern established in previous meetings of the series, eleven tutorial review papers were used to introduce (or to summarize) topics treated by thirty-eight contributed papers in a similar number of related sessions. These
The conference departed in two respects from previous practise: no 'poster' sessions were held, and the proceedings are to appear in book form. In retrospect the lack of poster sessions may possibly have contributed to the rather muted questioning of speakers. (In particular it seemed a pity that the cut and thrust of scientific debate was the exception, rather than the rule, at the close of
46
OPTICS AND LASER TECHNOLOGY. FEBRUARY 1980
the scheduled contributions). The second innovation simplifies the task of a review such as this: we shall highlight those papers which appear of general interest, and refer those interested in a detailed account of particular work to the conference proceedings, which will be published by John Wiley & Sons Ltd. The opening session featured two 'keynote' talks. The first, given by Arthur Schawlow and entitled 'The laser revolution', covered the wide variety of applications which have been proposed for lasers since their first invention. These included the 'death-rays' of the science fiction novelist, to a slightly more practical 'laser eraser' for typing or insect elimination! More seriously, the review briefly covered the now numerous engineering, chemical, telecommunications and medical applications of the laser and proceeded to the speaker's present scientific speciality: high-resolution spectroscopy. Here indeed there has been a revolution in both the resolution and sensitivity available to spectroscopists, using techniques such as Dopplerfree saturation spectroscopy and intermodulated fluorescence. Professor Bradley, giving the second of the two opening talks went on to speak of new lasers and la~er systems, in particular describing the free-electron laser and phaseconjugation techniques. He indicated a strong enthusiasm for the potential of the free-electron laser, noting a recent American proposal for such a laser with a capability of 12 kWcw in the visible. Phase conjunction he characterized as a technique permitting the construction of a 'magicmirror': one that exactly reverses the wave in such a way that aberrations introduced along an optical system are cancelled out over the return path. This concept is likely to find application in a number of field, including laser fusion and communication systems. The overall scene having been set, the conference moved on to discussing the details of atomic laser-spectroscopy, an invited talk by J.A.R. Griffith opening the session. This talk dealt with the use of heterodyne techniques applied to the resolution of isotope shifts in Samarium using dye lasers. Spectral resolution down to only 20 kHz was described. Contributed papers in this session included the observation of laser induced disappearance of Rydberg states (A.M. Scott, Hull University) and the resolution of structure in the far wings of HeI lines at intensities as low as 10-s of line centre (D.D. Burgess, Imperial College). P.L. Knight opened the nonlinear optics session with an invited paper detailing the multiphoton absorption effects ~hich result from near resonance of intermediate transitions. R. Wyatt went on to describe an order of magnitude improvement achieved in a Cs vapour stimulated Raman experiment using an additional heater to ensure dissociation of absorbing Cs2 dimers. The first of two sessions on lasers commenced with a discussion of a closed cycle 1 to 10 Hz iodine laser (H.J. Baker, Manchester), and proceeded through various papers on CO2 lasers. These ranged from the injection control of a kilojoule, e-beam system (A.C. Walker, Culham) through
OPTICS AND LASER TECHNOLOGY. FEBRUARY 1980
the stabilization of cw oscillators (S. Moffat, St. Andrews) down to the miniature wave-guide devices described by D. Hall in an invited talk rounding off the last session of the first day. The subject of laser-plasma interactions was dominated by contribution from the Rutherford Laboratory, Dr A.F. Gibson introduced the first of two sessions on this topic by summarizing the broad requirements for thermonuclear power production using inertial-confinement techniques. In his view, compression of simple spherical targets would be most readily achieved by using near-uv lasers; thus reducing unwanted target pre-heat from energetic electrons which are generated at longer wavelengths. American proposals for generating uv wavelengths at sufficiently high intensities included the possibility of OC Se photodissociation lasers, and (Raman) pulse-compression of the output from existing KrF lasers. He reiterated the potential advantages for beam-quality control which might accrue on layered targets at intensities of 5 x 1014 W cm -~ (at k = 0.53 #m) and 2 x 10 Is W cm -2 (at X = 1.06/am); similar bulk coronal electron 'temperatures' ( ~ 440 eV) and densities (~1022 cm-3) were measured, but the burn-depth was several times greater at the shorter wavelength. In a related experiment Bond et al showed that the 6 - 20 keV 'hot' electron component which causes this ablation accounts for some 0.1 ~ 0.2 of the incident energy; however in low-density ( ~ 0.1 gm cm -3) substrates spacecharge inhibited the effects of this fast electron preheat. In another experiment, time-resolved x-ray shadowgraphy had demonstrated ablatively-driven compressions to core densities > 10 gm cm -3, and had provided some evidence for (Rayleigh - Taylor) mixing of successive wall-layers on the microsphere target. The second of these sessions included a review by Professor Boyd on the theory of laser-plasma interactions. Other - generally excellent - invited papers included that by Professor Dixon on 'Laser spectroscopy' (which gave some feeling for the potential of infra-red lasers in studying the evolution of excited molecule states, a topic also covered by several contributed papers), and an interesting survey by Dr J.K. Wright of some industrial uses of Nd-YAG lasers. The Heriot-Watt home-team led by Professor S.D. Smith stimulated discussion, and some light (on 'Transphasor' action), with their interesting work on optical bistability in semiconductor crystals. Colourcentre lasers (H. Welling, Hanover) and x-ray lasers (G. Pert, Hull, brought the formal proceedings to a close Many individual scientific contributions, such as that by Dr. Vaughan on measuring the elastic properties of biological materials, cannot be adequately summarized in a 'snap-shot' report such as this. However, these, and the contacts established during the less formal proceedings, ultimately provide the rational for such meetings. The conference was fortunate in its choice of Edinburgh for its venue, and in Dr Brian Wherett for his hard work, organization and hospitality. I.J. Spalding, A.C. Walker
47
date for the most exciting application, ie endoscopic photocoagulation and the chairmen were quick to shoot down the one or two dubious papers which did appear. The main speakers were R.M. Dwyer (USA) and P. Kiefhaber (FDR). Their considerable practical experience was apparent and both, especially Kiefhaber, had taken great pains to classify their successes and failures during several years experience with the Nd: YAG laser. An interesting paper of Konigsmann (FDR) discussed the relative cutting and hemostatic effects of CO2, CO and Nd: YAG lasers. His results showed that the CO2 laser is best for cutting tissue and the Nd:YAG laser is best for sealing blood vessels. Other speakers showed that the Nd: YAG is superior to the Argon laser for sealing large blood vessels. A general point noticed during the congress was the increasing participation of Japanese speakers and delegates over the first two congresses. One speaker from Japan revealed that several million pounds is being spent in his country to develop second generation medical laser systems by 1981. Since the next congress will be held in Tokyo in 1981 it is easy to see that it will be almost completely dominated by the Japanese who clearly see a large market for such equipment. A technical exhibition was held during the conference with most of the well established manufacturers present. It was no surprise to find a CO2 laser system in a prominent position. Many delegates had great fun performing laser surgery on oranges and similar items; the complete absence of any shielding to prevent stray laser light being scattered all over the place was rather alarming. Indeed one exhibitor had a hole burned in the curtain at the back of his booth after a laser was left running accidentally! On the whole then, an unsatisfactorily conference. There is a major role for lasers in medicine but it will be a few years before sufficient reliable information will be available to sort out the really useful applications from the gimmicks. The conference proceedings will be published. A.F. Purdie
Fourth national quantum electronics conference Edinburgh, UK, 19-21 September 1979
scientific contributions were augmented by twenty exhibits of commercial laser and optical equipment, and by a conference bookstall. The exhibition was interesting, of excellent quality, and in our view contributed significantly to the general value of the meeting.
The fourth in a biennial series of conferences organized by the quantum electronics group of the Institute of Physics was held at Herriot-Watt University (Riccarton Campus), Edinburgh, from 19-21 September 1979. The meeting was co-sponsored by the Chemical Society and the IEE. The resulting interdisciplinary nature of the proceedings attracted an audience of over 200. Following a pattern established in previous meetings of the series, eleven tutorial review papers were used to introduce (or to summarize) topics treated by thirty-eight contributed papers in a similar number of related sessions. These
The conference departed in two respects from previous practise: no 'poster' sessions were held, and the proceedings are to appear in book form. In retrospect the lack of poster sessions may possibly have contributed to the rather muted questioning of speakers. (In particular it seemed a pity that the cut and thrust of scientific debate was the exception, rather than the rule, at the close of
46
OPTICS AND LASER TECHNOLOGY. FEBRUARY 1980
the scheduled contributions). The second innovation simplifies the task of a review such as this: we shall highlight those papers which appear of general interest, and refer those interested in a detailed account of particular work to the conference proceedings, which will be published by John Wiley & Sons Ltd. The opening session featured two 'keynote' talks. The first, given by Arthur Schawlow and entitled 'The laser revolution', covered the wide variety of applications which have been proposed for lasers since their first invention. These included the 'death-rays' of the science fiction novelist, to a slightly more practical 'laser eraser' for typing or insect elimination! More seriously, the review briefly covered the now numerous engineering, chemical, telecommunications and medical applications of the laser and proceeded to the speaker's present scientific speciality: high-resolution spectroscopy. Here indeed there has been a revolution in both the resolution and sensitivity available to spectroscopists, using techniques such as Dopplerfree saturation spectroscopy and intermodulated fluorescence. Professor Bradley, giving the second of the two opening talks went on to speak of new lasers and la~er systems, in particular describing the free-electron laser and phaseconjugation techniques. He indicated a strong enthusiasm for the potential of the free-electron laser, noting a recent American proposal for such a laser with a capability of 12 kWcw in the visible. Phase conjunction he characterized as a technique permitting the construction of a 'magicmirror': one that exactly reverses the wave in such a way that aberrations introduced along an optical system are cancelled out over the return path. This concept is likely to find application in a number of field, including laser fusion and communication systems. The overall scene having been set, the conference moved on to discussing the details of atomic laser-spectroscopy, an invited talk by J.A.R. Griffith opening the session. This talk dealt with the use of heterodyne techniques applied to the resolution of isotope shifts in Samarium using dye lasers. Spectral resolution down to only 20 kHz was described. Contributed papers in this session included the observation of laser induced disappearance of Rydberg states (A.M. Scott, Hull University) and the resolution of structure in the far wings of HeI lines at intensities as low as 10-s of line centre (D.D. Burgess, Imperial College). P.L. Knight opened the nonlinear optics session with an invited paper detailing the multiphoton absorption effects ~hich result from near resonance of intermediate transitions. R. Wyatt went on to describe an order of magnitude improvement achieved in a Cs vapour stimulated Raman experiment using an additional heater to ensure dissociation of absorbing Cs2 dimers. The first of two sessions on lasers commenced with a discussion of a closed cycle 1 to 10 Hz iodine laser (H.J. Baker, Manchester), and proceeded through various papers on CO2 lasers. These ranged from the injection control of a kilojoule, e-beam system (A.C. Walker, Culham) through
OPTICS AND LASER TECHNOLOGY. FEBRUARY 1980
the stabilization of cw oscillators (S. Moffat, St. Andrews) down to the miniature wave-guide devices described by D. Hall in an invited talk rounding off the last session of the first day. The subject of laser-plasma interactions was dominated by contribution from the Rutherford Laboratory, Dr A.F. Gibson introduced the first of two sessions on this topic by summarizing the broad requirements for thermonuclear power production using inertial-confinement techniques. In his view, compression of simple spherical targets would be most readily achieved by using near-uv lasers; thus reducing unwanted target pre-heat from energetic electrons which are generated at longer wavelengths. American proposals for generating uv wavelengths at sufficiently high intensities included the possibility of OC Se photodissociation lasers, and (Raman) pulse-compression of the output from existing KrF lasers. He reiterated the potential advantages for beam-quality control which might accrue on layered targets at intensities of 5 x 1014 W cm -~ (at k = 0.53 #m) and 2 x 10 Is W cm -2 (at X = 1.06/am); similar bulk coronal electron 'temperatures' ( ~ 440 eV) and densities (~1022 cm-3) were measured, but the burn-depth was several times greater at the shorter wavelength. In a related experiment Bond et al showed that the 6 - 20 keV 'hot' electron component which causes this ablation accounts for some 0.1 ~ 0.2 of the incident energy; however in low-density ( ~ 0.1 gm cm -3) substrates spacecharge inhibited the effects of this fast electron preheat. In another experiment, time-resolved x-ray shadowgraphy had demonstrated ablatively-driven compressions to core densities > 10 gm cm -3, and had provided some evidence for (Rayleigh - Taylor) mixing of successive wall-layers on the microsphere target. The second of these sessions included a review by Professor Boyd on the theory of laser-plasma interactions. Other - generally excellent - invited papers included that by Professor Dixon on 'Laser spectroscopy' (which gave some feeling for the potential of infra-red lasers in studying the evolution of excited molecule states, a topic also covered by several contributed papers), and an interesting survey by Dr J.K. Wright of some industrial uses of Nd-YAG lasers. The Heriot-Watt home-team led by Professor S.D. Smith stimulated discussion, and some light (on 'Transphasor' action), with their interesting work on optical bistability in semiconductor crystals. Colourcentre lasers (H. Welling, Hanover) and x-ray lasers (G. Pert, Hull, brought the formal proceedings to a close Many individual scientific contributions, such as that by Dr. Vaughan on measuring the elastic properties of biological materials, cannot be adequately summarized in a 'snap-shot' report such as this. However, these, and the contacts established during the less formal proceedings, ultimately provide the rational for such meetings. The conference was fortunate in its choice of Edinburgh for its venue, and in Dr Brian Wherett for his hard work, organization and hospitality. I.J. Spalding, A.C. Walker
47