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Optical Elements and Fibers

#G-1460


The Development of Doped AgCl Single Crystal and Fiber Growth Technology and Creating of the Mid-Infrared Optical Elements and Fibers for Transmitting Powerful Lasers Radiation

Tech Area / Field

  • PHY-OPL/Optics and Lasers/Physics
  • MAT-SYN/Materials Synthesis and Processing/Materials
  • PHY-SSP/Solid State Physics/Physics

Status
3 Approved without Funding

Registration date
21.09.2006

Leading Institute
Geological Institute, Georgia, Tbilisi

Collaborators

  • The State University of New Jersey RUTGERS / Material Science & Engineering, USA, NJ, Piscataway\nInstitute of Solid State Physics, Latvia, Riga

Project summary

The purpose of project is the development of stable to the visible and ultraviolet (UV) light doped AgCl crystal and fiber growth technology from the melt, creation of new optical materials of infrared (IR) range, fabrication of optical elements including single-crystal fibers of mid infrared range. These optical elements have great importance for the IR powerful laser radiation and radiation delivery systems.

Optical windows of infrared range are the most important elements for cell of photochemical reactors in which nonequilibrium chemical reactions on isotopes separation are realized. IR transmitting fibers are applicable for:

  • laser power delivery (there are many lasers Er:YAG, CO, CO2 that emit in the mid-IR spectral range. IR fibers are very useful for transmitting the laser energy);
  • IR spectroscopy. (fiberoptic evanescent wave spectroscopy is used as a tool for measuring the absorption spectra of substances. FEWS can be used in a verity of areas such as the identification of toxic substances, diagnosing diseases etc.);
  • thermometry (a fiberoptic radiometer can be used for non-contact temperatures measurements in a remote location);
  • thermal imaging (an ordered bundle of IR fiberoptics can deliver a thermal image even in places that are not in the direct line of sight). The main demands for such materials are as follows:
  • transparence in a wide range of infrared spectrum;
  • steadiness to the powerful laser radiation;
  • chemical stability to the influence of aggressive medium;
  • mechanical strength.

Quartz, sapphire, different glasses, semiconductors, ionic crystals are usually used as optical materials for the windows of low temperature cells. But these materials posses some disadvantages such as:
  • low mechanical strength;
  • hygroscopicity;
  • high reflection losses;
  • low steadiness in aggressive areas and in the conditions of cryogenic temperatures.

The usage of AgCl crystals for producing optical elements and crystalline fibers of infrared range are conditioned in the first place by their transparence in the wide range wave length from 0.5 to 23 mkm. Besides that AgCl crystals are nonhygroscopic, steady to the light aggressive areas and have unique mechanical properties. Our researches have shown that silver chloride optical windows are practically the only material steady to fluoride influence.

At the same time silver chloride possesses essential disadvantage restricting its usage. Under ultraviolet radiation and visible light irreversible processes of photolysis take place in AgCl crystals. They are photochemically decomposed, creating silver microparticles that cause absorption or scattering loss.

The Physical Crystallography Department of the Alexander Janelidze Geological Institute of the Ministry of Education and Sciences of Georgia is one of the leading institution of the former USSR (and, in fact, the only one in Georgia) carrying out both scientific research in the field of preparation of IR optical materials, laser and scintillation single crystals and development of technological processes of their growth and launching of their industrial production. During the last years we have been working out the technology for growth of silver chloride crystals doped by special additions. This will help us to get rid of the most disadvantages. The investigation of the photolysis processes in the presence of dope additions will make it possible to define the optimal compound, which will help to get maximal stability of material to the influence of ultraviolet radiation. As it is clearly seen from our researches it is quite possible to overcome the difficulties connected with photolytic properties of AgCl by the introduction stabilizing additions into the crystal structure.

As a result of the presented project fulfillment the following results are expected:

  • technologies of creation high quality optical elements and fibers in the mid infrared region should be developed;
  • growing of large crystals and fibers of doped AgCl and fabrication of high quality optical elements and fibers for mid infrared range;
  • physical and optical properties of grown doped AgCl crystals and fibers will be investigated.

The realization of work on creating new optical materials of infrared range within the framework of project should reveal area of applied researches, where the application of optical items from AgCl is especially expedient, that would help to ensure long-term sales of these science capacity items, for which production the present project creates a scientific technological base in Georgia. These works envisage also improvement of growth installations, the use of complex methods and equipment for studies of optical and physical characteristics in a broad temperature range, determination of phase composition and content of dopand elements in the crystals.

In the course of the work on the project the following tasks should be realized:

  • the development of the technology of growing of doped AgCl crystals;
  • the investigation of the influence of univalent and bivalent dopes on the photolysis kinetics and mechanical properties of AgCl crystals;
  • the investigation of photolysis processes in AgCl crystals with dopes for control these processes, in particular, to stabilize and restore crystal properties;
  • the investigation stabilizing influence on light sensitivity of dopes in AgCl crystals;
  • growing large crystals of high quality AgCl with univalent and bivalent dopes;
  • the fabrication of high quality optical elements for mid infrared range;
  • the research of optical and mechanical properties of doped AgCl-plates at the wave length from 0.5 to 20 mkm;
  • the research of the steadiness of the doped AgCl crystals to the powerful laser radiation;
  • the research of the bulk and surface absorption by the laser calorimetric method;
  • the development of the technology of continuous growing doped silver halide single-crystal fibers from the melt;
  • the manufacture of different cross-section single-crystal fibers in a bare core structure with loose polymer jacket;
  • the characterization of grown fibers, such as transmission range, attenuation at 10.6um, effective numerical aperture, laser (CO­2) damage threshold tensile strength, minimum bending radius and other parameters will be measured.

Testing of the optical elements and fibers developed under the present project is to be carried out in collaboration with such companies as: - Ceramic Science & Engineering, Fiber Optic Materials Research Program, Rutgers University, Martinsville, NJ, USA; - Division of Disordered Material Physics, Institute of Solid State Physics, University of Latvia, Riga; - Institute of Molecular Physics Russian Research Center “Kurchatov Institute”; - School of Physics and Astronomy, Tel Aviv University, Tel Aviv, Israel.

After the development will have been completed, industrial production of doped AgCl crystals is planned to be launched as well as production of IR optical elements and fibers based on them. This production will not only fully meet the demand of Georgia, but also ensure large-scale export supplies to a number of companies in other countries.

For carrying out of the planned works the Physical Crystallography Department of the Alexander Janelidze Geological Institute of the Ministry of Education and Sciences of Georgia possess the necessary technological and research equipment, groups of highly skilled scientists, engineers, technologists, who had worked earlier in military-related fields, such as: development of materials for laser separation of isotopes, including uranium; development of solid state lasers for military applications; creating materials for IR optics, laser technology and atomic energetics for military applications in space programs. They have large experience in development of unique technologies and instruments for special purposes, in research, development and launching of industrial production of single crystals and fibers based on them.

The participants of the present project have fulfilled International Project ISTC number G-049 (1998-2000) with a title “The Powerful Waveguide Laser”, International Project STCU number Gr-48(J) (2003 – 2005), with a title: “ Perspective scintillators based on activated gadolinium and lutetium oxyorthosilicate single crystals and detectors for nuclear spectrometry and positronic emission tomography.”


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The International Science and Technology Center (ISTC) is an intergovernmental organization connecting scientists from Kazakhstan, Armenia, Tajikistan, Kyrgyzstan, and Georgia with their peers and research organizations in the EU, Japan, Republic of Korea, Norway and the United States.

 

ISTC facilitates international science projects and assists the global scientific and business community to source and engage with CIS and Georgian institutes that develop or possess an excellence of scientific know-how.

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