- Email: [email protected]
Laser damage conference
Chapters 5 and 6 discuss resonators and phase conjugation. It is the latter that attracts many to the subject: the notion that one can ‘time-reverse’ waves and thereby undo distortions in optical systems. There is a good description of the various possible mechanisms of selfpumped phase conjugators. Chapter 7 develops the diffraction properties of gratings in photorefractive media and the following chapter is devoted to volume holography. The remaining chapters deal with potential applications in interferometry, optical ‘computing’ and various other fields. The problems, as mentioned earlier. are that photorefractive media are not very sensitive (however you choose to define sensitivity), are physically small (useful dimensions of typically 10 x 10 x 10 mm3) and
Laser Damage NIST,
Chris Dainty Imperial College
Conference
Boulder, Colorado, 24-26 October 1994
This conference, which is the main conference dealing with all aspects of the power and energy handling capabilities of optical materials and components, was attended by 112 scientists, all engaged in the high-power laser field. Eighty papers were presented (39 read, 41 poster) over the three-day period and these, as usual, covered the fields of laser and optical component materials, laser induced damage measurements and characterization, thin film deposition and characterization, and fundamental mechanisms. In addition, there was a special mini-symposium on diamond optics for high-power lasers. Both the attendance and the bias of the papers have oscillated over the years. This year the main emphases were on diamond and on the test and supply of ultra-violet resistant optical materials for the ultra high-power, short-wavelength fusion lasers, The main problem with these lasers is that the short wavelengths induce colour centres in most materials, which result in the presence of highly transient excited state absorption. The mini-symposium on diamond optics indicated that although both Type IIa and CVD grown materials are superior to other materials in terms of dual band transmission, both laser and mechanical hardness and thermal shock resistance, these properties are not so superior as to make the use of them mandatory. Either the cost per substrate must reduce or the numbers of components ordered must increase markedly if the technology is to be used to its full potential. It is relevant to note that the best CVD grown material is now equal in terms of laser hardness to that of natural Type IIa diamond and that the VNIR LIDTs of this material have
0030-3992/95/$10.00 xiv
expensive ($lOOOs), so that in most proposed applications there are other much cheaper and more effective technologies available now. Strangely enough, one of the most promising areas of application in optical metrology and vibration analysis is not discussed. The book was written from notes prepared for a graduate course and a few problems are given at the end of each chapter (but there are no solutions). It would be an excellent text for a course on photorefractives, perhaps supplemented by one the volumes from the Leningrad School. All in all, I thoroughly recommend Yeh’s book.
been shown to be dominated by the - 5 pm second-order phonon intrinsic absorption band. The main remaining problems (after those of cost and markets) are the protection from high ambient temperatures (in the presence of oxygen) and the necessity for developing efficient AR coatings. It was argued that both problems could be overcome by the use of transmissive nitrides (for example, BN and Si,N,) and some research is being done on these coatings. One of the great steps forward, in terms of depositing high quality oxide coatings, was that it was shown that it is possible to deposit these at room temperature using vapour phase precursors. The other high point of the conference was that there were several papers discussing, both from experimental and theoretical viewpoints, the variation of the LIDT with pulse duration. It was demonstrably shown that below 30 ps the rate of ionization of the laser induced plasma dominates the damage process and that, in radiation hard materials, the laser beam energy density required for breakdown increases as the pulse length decreases. This was first predicted in 1969 but only now has the experimental evidence been available. The date for the 1995 symposium has already been set for the 30-31, October and the 1 November at NIST, Boulder. Colorado. Although giant strides have been made over the years in understanding the power handling capacity of laser component materials there is plenty of scope for useful advances still to be made. It will be interesting to see what topic dominates the next symposium.
@ 1995 Elsevier Science.
R. M. Wood All rights
reserved Optics
& Laser Technology Vol 27 No 2 1995
Laser Damage NIST,
Chris Dainty Imperial College
Conference
Boulder, Colorado, 24-26 October 1994
This conference, which is the main conference dealing with all aspects of the power and energy handling capabilities of optical materials and components, was attended by 112 scientists, all engaged in the high-power laser field. Eighty papers were presented (39 read, 41 poster) over the three-day period and these, as usual, covered the fields of laser and optical component materials, laser induced damage measurements and characterization, thin film deposition and characterization, and fundamental mechanisms. In addition, there was a special mini-symposium on diamond optics for high-power lasers. Both the attendance and the bias of the papers have oscillated over the years. This year the main emphases were on diamond and on the test and supply of ultra-violet resistant optical materials for the ultra high-power, short-wavelength fusion lasers, The main problem with these lasers is that the short wavelengths induce colour centres in most materials, which result in the presence of highly transient excited state absorption. The mini-symposium on diamond optics indicated that although both Type IIa and CVD grown materials are superior to other materials in terms of dual band transmission, both laser and mechanical hardness and thermal shock resistance, these properties are not so superior as to make the use of them mandatory. Either the cost per substrate must reduce or the numbers of components ordered must increase markedly if the technology is to be used to its full potential. It is relevant to note that the best CVD grown material is now equal in terms of laser hardness to that of natural Type IIa diamond and that the VNIR LIDTs of this material have
0030-3992/95/$10.00 xiv
expensive ($lOOOs), so that in most proposed applications there are other much cheaper and more effective technologies available now. Strangely enough, one of the most promising areas of application in optical metrology and vibration analysis is not discussed. The book was written from notes prepared for a graduate course and a few problems are given at the end of each chapter (but there are no solutions). It would be an excellent text for a course on photorefractives, perhaps supplemented by one the volumes from the Leningrad School. All in all, I thoroughly recommend Yeh’s book.
been shown to be dominated by the - 5 pm second-order phonon intrinsic absorption band. The main remaining problems (after those of cost and markets) are the protection from high ambient temperatures (in the presence of oxygen) and the necessity for developing efficient AR coatings. It was argued that both problems could be overcome by the use of transmissive nitrides (for example, BN and Si,N,) and some research is being done on these coatings. One of the great steps forward, in terms of depositing high quality oxide coatings, was that it was shown that it is possible to deposit these at room temperature using vapour phase precursors. The other high point of the conference was that there were several papers discussing, both from experimental and theoretical viewpoints, the variation of the LIDT with pulse duration. It was demonstrably shown that below 30 ps the rate of ionization of the laser induced plasma dominates the damage process and that, in radiation hard materials, the laser beam energy density required for breakdown increases as the pulse length decreases. This was first predicted in 1969 but only now has the experimental evidence been available. The date for the 1995 symposium has already been set for the 30-31, October and the 1 November at NIST, Boulder. Colorado. Although giant strides have been made over the years in understanding the power handling capacity of laser component materials there is plenty of scope for useful advances still to be made. It will be interesting to see what topic dominates the next symposium.
@ 1995 Elsevier Science.
R. M. Wood All rights
reserved Optics
& Laser Technology Vol 27 No 2 1995