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Light Beams Apodization

#0651


Development of the Nonlinear Optical Element for Light Beams Apodization and Large Aperture Laser Amplifiers Decoupling

Tech Area / Field

  • PHY-OPL/Optics and Lasers/Physics

Status
8 Project completed

Registration date
28.05.1996

Completion date
11.01.1999

Senior Project Manager
Malakhov Yu I

Leading Institute
VNIIEF, Russia, N. Novgorod reg., Sarov

Supporting institutes

  • FIAN Lebedev, Russia, Moscow\nNIOPIK (Organic Intermediate Products and Dyes), Russia, Moscow

Collaborators

  • University of Electro-Communication / Institute for Laser Science, Japan, Tokyo

Project summary

The objective of the Project is to create a new high-aperture optical decoupling element for powerful lasers at the simultaneous improvement of the beam spatial structure.

In order to avoid the serf-excitation in high-power laser systems with different wavelengths the active (Kerr, Pockells and Faraday cells) and passive (sprayed bismuth layers, iodine shutters, crystals with color centers, dyes in a polymer matrix and liquid solutions) optical decoupling elements are presently used. The active-type units are of higher contrast (the ratio between the transmission in the "open" and "closed" states), although they require additional control systems, and they are very expensive in high-aperture amplifiers. The passive-type units do not require any external control electrical signals, however, not all units of this type are convenient in operation. For example, in iodine lasers the bismuth elements are, in principle, of single use, the iodine shutter is difficult in service (it requires homogeneous heating of large volumes up to the temperatures ~900 °C). In neodymium lasers the crystals with color centers and the dyes in polymer matrices have no high contrast and photostability.

The advantage of the elements based on liquid dyes lies in their practically infinite operating light aperture. The use of the dye requires a hermetic cell of high optical quality. Moreover, there appears a possibility to realize the regime of the beam spatial structure improvement by cell design choosing. Usually such an improvement in lasers is achieved with the help of a so-called "soft" aperture diaphragm. In the offered Project we propose for the first time to combine the properties of passive decoupler with the properties of soft diaphragms in one element of laser installation. For this purpose it is necessary to form such layer of the bleaching liquid, which would absorb effectively the peripheral part of the incident beam with the decreased energy density due to a nonlinear dependence of the absorption coefficient.

In our work we make use of the earlier developed bleaching dyes solutions for various laser wavelengths. The large-aperture cells will be created on the basis of deep optical contact technology, which will provide a significant increasing of dyes stability and lifetime. This will also make the operation of the large high-power laser systems more ecologically pure.

The Project involves a theoretical and experimental study of the problems of interaction between the beams of a complicated shape and the nonlinear media.

Expected results

The result of the Project is to be a principally new apodizing-decoupling unit with the aperture up to 200 mm. Said decoupling type can be used in high power neodymium, iodine and excimer laser systems.

As a result of experimental decoupling element studies the new data will be obtained, which is of significant scientific interest.

Technical approach and methodology

The offered Project is based on the experience stored by RFNC-VNIIEF, SSC RF NIOPIK and FIAN specialists in research of physical processes taking place at powerful laser radiation interaction with matter, creating multicascade laser systems, developing nonlinear absorbing materials and designing of optical elements with the use of modem materials and technologies.

The investigations within the framework of the present Project will be carried out on the experimental facilities located at VNIIEF, NIOPIK and FIAN and equipped with up-to-date complexes of diagnostic and measuring devices.

In the process of the Project the results of studies are supposed to be presented in the form of reports at the international scientific conferences and seminars, discussed during the working meetings with foreign collaborators.

Expected foreign collaboration

Several foreign laboratories, such as Institute for Laser Science, University of Electro-communications, Tokyo, Japan and Max-Plank-Institut Fur Qauntenoptik, Garching, Germany, dealing with laser physics, have expressed an interest to the scope of the Project. The executors of the Project have established contacts with the employees of these laboratories and during the course of the Project intend to collaborate with them in the form of consultations and discussions of the results obtained.


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