High Power Technological Lasers
High Power Technological Lasers with Self-Adaptive Resonators
Tech Area / Field
- PHY-OPL/Optics and Lasers/Physics
3 Approved without Funding
VNIIEF, Russia, N. Novgorod reg., Sarov
- Russian Academy of Sciences / Institute of Applied Physics, Russia, N. Novgorod reg., N. Novgorod
- QinetiQ, UK, Malvern\nSchafer Corporation, USA, NM, Albuquerque\nAir Force Research Laboratory(AFMC)/DELG, USA, NM, Kirtland\nElectro-Optics Research Center TRW, USA, CA, Redondo Beach\nLasers,Plasmas and Photonic Processes Laboratory(LP3), France, Marseille\nLawrence Livermore National Laboratory, USA, CA, Livermore
Project summaryThe purpose of the proposed project is to construct high power technological lasers of a new type (average more than 500W) on the basis of self-adaptive resonators, which are adjusted to attain diffraction quality radiation with nonhomogeneous laser media or fundamental traverse mode, taking the whole volume of homogeneous laser medium of large cross section. The adjustment of these self-adaptive resonators for obtaining given spatial radiation parameters should be automatically controlled by the generation of volume dynamic holographic gratings in nonlinear media with the help of laser radiation itself. Research has demonstrated that lasers with self-adaptive resonators on the basis of dynamic volume holographic gratings can have unique properties. These include large average radiation power at high beam quality, stability of propagation direction and long coherence length. There is a distinct lack of lasers with such potential on the market.
The object of the proposed project will be to investigate the processes, responsible for the appearance and dynamics of the development of volume structures of refraction coefficient, of gain coefficient, induced by radiation of oxygen iodine and Nd-lasers in media with significant electrical striction nonlinearity and in Nd-laser crystals themselves at stimulated scattering and four-wave mixing (FWM). The effects of nonlinear refraction and self-action of radiation will also be the object of the project investigation.
The results on forming laser resonators at stimulated Brillouin scattering (SBS), recently obtained by the project participants, research of the instabilities and parametric phase conjugation (PC) in laser amplifiers, have demonstrated the potential for integrating the named nonlinear processes and ordinary laser media on luminescent centers into the unified functional system with feedback, the hybrid laser. The process of generation in the hybrid laser should be developed simultaneously with the creation, with the produced radiation itself in nonlinear media volume, holographic gratings with certain spatial characteristics, which permit these gratings to operate as PC-mirrors in the laser resonator. High noise characteristics (determined by luminescence) of laser media with inverse population, exciting the hypersonic grating with the opposing beams in the media with striction nonlinearity, allow a decrease in the excitation threshold for nonlinear effects and the production of hybrid laser oscillation on laser media with low gain coefficients and low levels of pumping. For example, it enables Nd lasers to produce radiation with average power of 200-250 W and above, and chemical oxygen-iodine laser to potentially operate on zero mode (on lateral index) with resonators, having a large Fresnel number. In addition, laser media and nonlinear media, used for SBS excitation, are transparent in the wide range of the spectrum. The gratings recorded in this media have high forming velocity (s and below). Such peculiarities of nonlinear media allow one to extend the spectral range of hybrid laser radiation and to obtain new operation qualities.
Taking into account the considerable volume of research, carried out by various teams over the world, one should note, nevertheless, that the physics of nonlinear optical processes in active laser media, the opportunities of technical application of already familiar nonlinear-optical phenomena, problems of intracavitary interaction between radiation and induced volume structures are still not clearly understood. At the same time, existing interest in high power technological lasers (Nd, chemical oxygen iodine lasers) with a high-quality radiation beam for precision treatment of industrial products stimulates hybrid laser research. This requires a clear understanding of nonlinear optical processes, which take place in nonlinear media, and of opportunities for their application in hybrid lasers.
The prospects of creating technological hybrid lasers with high radiation quality are very attractive. In the context of the project we plan to perform fundamental research of hybrid laser physics, to create adequate calculative-theoretical models of hybrid laser operation and to bring them to a level of engineering calculative methods. The result of these activities will be the creation of experimental prototypes of commercial hybrid lasers.
The project participants represent two leading scientific schools in Russia. They have long-standing experience of cooperation and are now deeply involved in laser technology and nonlinear optics.
In the process of project realization we will perform activities, the results of which will be useful for any types of laser (gas, solid state etc.). However, our main efforts will be directed towards the creation of solid state and iodine-oxygen hybrid lasers, capable of satisfying the demands of modern technologies.
We plan to obtain the following results, which are of fundamental importance
- Peculiarities of resonance nonlinearity for the most promising laser crystals, used for building high power lasers with diode pumping, will be investigated. In particular, it is supposed to research nonlinear polarizability of laser crystals (such as Nd:YAG; Yb:YAG). It depends upon different polarizability of excited and non-excited ions-activators of Nd3+ and Yb3+ under the condition of strong diode and lamp pumping.
- The effects of multiphoton absorption and absorption from the excited state in laser crystals, containing Nd3+ ions (Nd:YAG, Nd:YAP, Nd:YVO) and Yb3+ ions (Yb:YAG) and also in Nd3+ - containing laser glasses at various types of pumping (diode, laser, lamp pumping) will be studied.
- It will be determined under which conditions resonance nonlinear refraction and light beam self-action (with pulse duration from nanoseconds to millisecond), plus stimulated resonance scattering in laser amplifiers on the base of crystals with large gain coefficient will take place.
- Mechanisms, responsible for fundamental mode selection and conditions of their efficient operation at the SBS of opposing beams in photo-dissociated iodine and chemical oxygen iodine laser resonators, and the influence of optical non-homogeneities of the laser medium itself on dynamic resonator formation will be determined. Measurements of possible optical non-homogeneities, appearing in the SBS medium, will be performed. Their part in the process of SBS for opposing beams will be investigated.
- Possible applications of dynamic gratings, excited by light waves at nonlinear media, for beam spatial-temporal parameter control in laser oscillators will be determined. Radiation self-organizing effects in the new type of lasers (hybrid lasers), the resonators of which are formed with the help of dynamic holograms induced by the oscillated beams themselves, will be studied. The adaptive properties of such resonators in compensating laser medium optical distortions are to be researched.
The results of the following research must have great applied value for developers of new laser systems:
- Determining the physical principles of laser design (both with lamp and diode pumping), which has dynamic resonators based on nonlinear holographic mirrors, and their technical opportunity to produce radiation with high (average on time) power (more than 500 W) and with beam quality, close to diffraction limit.
- Creation of an operating model of a hybrid solid state laser with dynamic resonator on the basis of holographic mirrors, capable of producing radiation with an average power of 500 W and more with beam quality, close to diffraction limit, with stable direction of propagation and large coherence length.
- Demonstration of the potential to produce diffraction quality radiation with a chemical oxygen-iodine laser with large aperture dynamic resonator.
Lasers with such radiation parameters can be applied widely. In particular, they can be used for precision material treatment, for projection photolithography, for remote probing of the atmosphere, in scientific research and for controlling thermonuclear fusion.
It is planned to achieve the project purposes through the following series of steps. The following has to be performed:
1. To research resonance nonlinearity for certain laser crystals (Nd:YAG; Nd:YAl03, Nd:YVO4 and Yb:YAG) at lamp and diode pumping;
2. To research laser crystal luminescence spectra in the range of violet-green wavelengths under the combined influence of laser and diode pumping;
3. To research lasers on crystals (both with lamp or diode pumping), with dynamic resonators, capable of producing high-power beams (average on time) with high quality.
4. To research photodissociative iodine and chemical oxygen-iodine laser with dynamic resonator on the basis of the SBS of opposing beams in compressed Xe. To research the SBS of opposing beams beyond the laser resonator.
5. Theoretical analysis and calculation simulation of the processes, which take place in the formation of the phase conjugated mirror of the dynamic resonator at the SBS of opposing beams of produced radiation in photodissociative iodine and oxygen iodine lasers.
6. To measure optical non-homogeneities, induced by laser radiation, in compressed Xe. To research the influence of these non-homogeneities on hybrid iodine laser operation.
7. To research hypersonic iodine laser, with large aperture dynamic resonator (Fresnel Number N >> 1).
The results, obtained from these investigations, can be presented to companies, which manufacture industrial lasers and, primarily, to collaborators, participating in the project, after project completion.
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