SU1308131A1 - Method of obtaining laser active medium - Google Patents

Abstract

The invention relates to the field of quantum electronics and can be used to create active elements and passive gates in lasers. The aim of the invention is to increase the efficiency of the laser while simultaneously expanding the spectral range of generation. To achieve the delivered Delhi, the crystal is optically processed, then the crystal is placed in a cadmium container and the container is introduced into the core of the other reactor. After that, the crystal is heat treated in the temperature range from 600 to 700 K for a time of Not more than one and a half hours. Then the crystal is irradiated with J-radiation of a certain dose and re-heat treated. This makes it possible to increase the laser efficiency by up to 17%, according to puff generation in the visible region of the spectrum. WITH about 30 with

Description

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The invention relates to the field of quantum electronics and can be used to create active elements used in lasers with tuning the frequency of radiation, and passive gates of mono pulsary lasers.

The aim of the invention is to increase the efficiency of the laser while simultaneously expanding the spectral range of generation.

Generation expands to visible and near infrared radiation,.

As a result of the shock mechanism of interaction, fast neutrons cause the formation of a large number of defects such as displacements in a crystal. With integral fast neutron fluxes of less than 10 N cm, the concentration of defects is insufficient to give the crystal further properties necessary for obtaining the generation. When flows over

10 ° n-cm begin to deteriorate mecha- j. - The nical properties of the crystal. Besides

Moreover, irradiation with such streams increases the cost of fabricating the medium. However, only neutron irradiation in the specified range of fluxes does not allow the creation of color centers in the crystal that are suitable for creating an active medium. Defects such as offsets are varied. They include cationic and anionic vacancies, inter-

narrow atoms and ions. In addition, at the capture of anion vacancies of electrons, single-color centers are formed. However, these color centers determine absorption in the ultraviolet region of the spectrum.

To create dvuhvakantnyh color centers, optical transitions in which provide the imparting the necessary properties to the environment, it is necessary 1-1m heat treatment for 1-1 j5 h at a temperature of 600-700 K. in a crystal, they are attached to single color centers, forming two-vacancy. An increase in the annealing temperature of 700 K leads to a partial destruction of the color centers,

heat treatment provides a multiple increase in the concentration of color centers 5 with maximal absorption bands of about 450, 570, 670 j

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850 nm. Annealing is also possible at shorter times, however, taking into account the high inertia of heat sources during heat treatment and the expediency of obtaining reproducible results, a time interval of 1-1.5 hours is selected.

The absorption and emission of light by the color centers responsible for the occurrence of absorption bands with maxima of 670 and 850 nm determines the possibility of tuning the wavelength of the generated radiation. To increase the concentration of these color centers, the crystal is irradiated with f-quanta with a dose of 26-260 Cl; kg and re-heat-treated at a temperature of 720-770 K for 1-1.5 hours. By carrying out this procedure, it is possible to almost double the concentration of centers absorbing in the region of 850 nm, and 10-20% - centers absorbing in the region of 670 nm. After neutrons are irradiated in a crystal, a limited number of one-vacant centers occur, containing 2.3 or more electrons. Therefore, during the first heat treatment, after the addition, vacancies form, with a relatively small number of centers absorbing in the 670 nm region, and even smaller centers absorbing in the 850 nm region. With γ irradiation of ethic crystals, the redistribution of electrons between the two-vacancy centers already occurs, and the concentration of centers with a large number of electrons increases. For this process, a radiation dose of 26 to 269 Kl-kg is sufficient. At doses less than 26 Kl, dynamic equilibrium over electronic states does not have time to establish, which ensures an increase in the concentration of centers. Doses of more than 260 kg-kg have no practical feasibility. However, when γ-irradiation, as at the beginning with the neutron one, inactive absorption by other defects also occurs. To eliminate them, heat treatment is repeated at temperatures of 720-, 770 K for 1-1.5 hours. At the same time, there is no need to increase the annealing temperature above 770 K, and at temperatures less than 720 K, the defects responsible for residual absorption do not have time to anneal during this period. of time.

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Example 1. The fSepyr sapphire crystal with a thickness of 10 mm produces its optical processing. After this, the treated crystal is placed in a metal cadmium container (wall thickness not less than 1 mm). Cadmium cuts off the thermal part of the neutron spectrum, which makes it possible to significantly reduce the level of induced crystal activity due to a decrease in its activation by thermal neutrons. The container with the crystal is placed in the active zone of the nuclear reactor and the crystal is irradiated with fast neutrons with an integral flux.

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10 H CM. After irradiation, the container with the crystal is removed from the fieaKTopa core and placed in a repository of radioactive substances, in which it is kept for about 2 months to reduce the induced radioactivity. After this time, the crystal is removed from the container and the dosimetric devices determine the level of residual radioactivity, which should not exceed certain standards. The decontamination of the surface of the irradiated crystal, which consists in processing it with ethyl alcohol and distilled water, is then carried out to remove surface radioactive contamination.

After heat treatment for one hour at 650 K, absorption bands with maxima at 570, 670 and 850 nm appear in the spectrum. After irradiation with a dose of 26 Kl. and heat treatment for one hour at 720 K, the concentration of centers responsible for absorption in the bands with maxima at 670 and 850 nm, increases markedly.

Note E. p. An active element made of sapphire crystal 1 cm thick, irradiated with a stream of fast neutrons of 10 n-cm and aged 2 months in storage, was excited by a dye laser with a power density of 100 MW-cm at a wavelength of 450 nm. In the resonator with mirrors,. having a reflection coefficient of 0.09, the pump radiation did not achieve the generation threshold. After heat treatment at 700 K in

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during 1.0 h the threshold i (games. and (in Oyl exceeded three times.

Example L, Mmm: Lemeite from a sapphire crystal (HM) 1 cm, irradiated with a stream of fast neutron 10, aged 2 months in storage, in a resonator with an entrance mirror with a reflection coefficient of 0.65, excited by a single-pulse laser on a ruby with a monopulse laser with a ruber 0 MW. Get geyasheyu failed.

After heat treatment at 700 K, radiation was generated in the region of the spectrum at about 818 nm with an efficiency of about 10%. 11 After irradiation with a dose of 50 C / kg and heat treatment at a temperature of 720 K, a laser efficiency of 31% is achieved.

Example 4. The active element of sapphire crystal with a thickness of 1 cm, irradiated by a stream of fast neutrons

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10 and / cm, sustained for 2 months in a repository in a resonator with an output mirror having a reflection coefficient of 0.85, was quasi longitudinally excited by a dye laser with a power density of 120 MW-cm at a wavelength of 840 nm. Radiation generation was not received.

After heat treatment at a temperature of 720 K, a laser efficiency of 7% is achieved. After y irradiation with a dose of 26 C / kg and heat treatment at a temperature of 750 K, the laser efficiency increased to 17%.

These crystals can also be used for passive gates of monopulse lasers.

Claims (1)

Invention Formula The method of obtaining the active medium of a laser, including irradiating a cypfir crystal with a neutron flux, is so tampered with the fact that, in order to increase the laser efficiency with a simultaneous expansion of the spectral generation range, after irradiation of sapphire crystals, heat treatment is performed at a temperature of 600-700 K for 1-1.5 hours, irradiated with γ-radiation with an exposure dose of 26 - V 260 Kl.kg and repeated heat treatment at a temperature; round 720 - 770 K for 1-1.3 hours Circulation Subscription