CS269349B1 - Method of yttrium-aluminium perofskite preparation for lasers with high mean power - Google Patents

Abstract

The object of the present invention is to prepare yttritohlinltó perovskitu activated neodymium for high average lasers performance. Prepared single crystals ss grown by melt drawing under the atmosphere containing free, hydrogen with a range of partial pressure from 10 to 10 Pa. then tempering in the following manner. First, the ss is tempered under vacuum with pressure residual gases of less than 0.1 Pa at at 1500 to 1800 ° C for 2 to 18 hours hours. This is followed by tempering in the atmosphere contain! free oxygen with partial pressure 104 to 10 ° Pa at 1400 to 1700 ° C for 5 to 24 hours and finally under vacuum with residual gas pressure As 0.1 Pa at 1100 to 1450 ° C for 3 to 25 hours.

Description

The present invention relates to a process for the preparation of activated alumina; neodymium ions e very low absorption at the laser emission wavelength at long-term intensive pumping with light from lamps, and therefore suitable for lasers and high average power.

Neodymium-activated yttrium-aluminum perovite single crystals exhibit a number of laser properties compared to the commonly used yttrium-aluminum garnet, which facilitate the construction of lasers with advantageous parameters. They are polarized output, option ^1! Achieve shorter and stronger keying pulses and the laser generation to the entire range of wavelengths. The practical applicability of this material is reduced by the presence of a number of defects, of which the formation of color centers during intensive optical pumping is a factor that significantly reduces the average output power of lasers. The radiation-induced color centers increase both the inactive absorption in the pumping region and at the laser emission wavelength, which increases both the thermal deformation and the 1 loss coefficient of the laser rods.

These shortcomings can be overcome by a process for the preparation of neodymium-activated yttrium-aluminum perovite for high average power lasers according to the invention, characterized in that the single crystals are grown by melt drawing under an atmosphere containing free hydrogen at a partial pressure of 10 to 10 Pa, then tempered in vacuo. residual gas pressure of less than 0.1 Pa at a temperature of 1500 to 800 ° C for 2 to 18 hours, further in an atmosphere containing free oxygen with a partial pressure of 10 to 10 Pa at a temperature of 1,400 to 1,700 ° C for for 5 to 24 hours and finally in a vacuum with a residual gas pressure of less than 0.1 Pa at a temperature of 1,100 to 1,450 ° C for 3 to 25 hours. By growing under these strongly reducing conditions, single crystals completely free of iron are prepared, which absorbs relatively strongly in the region of 1yum, but with an excess of metal ions, especially yttrium, which results in broadband absorption. Excess metal ions are removed by high temperature vacuum tempering, but some of the oxygen ions are replaced by colored F ⁺ centers. Tempering in an oxygen-containing atmosphere occupies most of the P ⁺ centers or anionic vacancies with oxygen, but the relative excess of oxygen is manifested externally by the existence of colored 0 ions. The final low-temperature tempering in vacuum decomposes the oxides on the surface of the single crystals, with oxygen escaping and relatively small aluminum atoms diffusing into the single crystal, where 0 ions are bound, which are converted to 0 ions. The resulting grid contains metal and oxygen ions in exactly a stoichiometric ratio with a slight content of vacancies, which results in the resistance of the material to irradiation with the light of the lamps, because there is practically no transmission of charge carriers. In the thus prepared single crystals, the absorption of a photon on neodymium ions converts its electrons only to quantum states, not to capture centers outside the neodymium ions, and therefore the energy of photons is used only to pump neodymium ions and not to form color centers.

In this way, it is therefore possible to prepare yttrium-aluminum perovskite, activated by neodymium ions, which is particularly suitable for lasers with high average power.

Example 1

Single crystals of yttraluminium perovekite with a content of 0.6 wt. % of neodymium were grown by drawing from the melt in the axial direction in an atmosphere containing 70% by volume of Ar and 30% by volume of H ₂ with a total pressure of 0.12 MPa. After cultivation, the single crystals were cut into chips measuring 7x7x110 mm. The chips were heated under vacuum with a residual gas pressure of 10 ° C at 1720 ° C for 5 hours. By this tempering the brown shade, typical for single crystals grown in a reducing atmosphere, disappeared, part of the chips were processed into laser rods with a diameter of 5 mm and a length of 100 mm. When pumping 5 M in a laser with an output mirror with a reflectance of 92%, an output power of 60 W was obtained with these rods. Most of the chips were further tempered in air at 1,520 ° C for 14 hours. The test laser rod of the thus tempered single crystals provided only 3OW under the same conditions as in the previous case. Subsequent tempering in a vacuum with a residual gas pressure of 10 ^- Pa Pa at a temperature of 1,310 ° C for 10 hours adjusted the spectral properties of the chips to such an extent that

The laser rods made therefrom made it possible to obtain in said laser at the same rate. nek power 1O5W. By omitting some of the above tempered, a material with inferior laser properties than indicated was always obtained.

Example 2

Single crystals of yttrium-aluminum perovskite with a content of 1.85 wt. % neodymium were grown by melt-drawing in the direction of the crystallographic axis (001) below. a protective atmosphere containing hydrogen at a partial pressure of $ 3.10 Pa and helium at a partial pressure of $ 1.08.10 Pa. The single crystals were cut into 10x10x90 mm chips and these were first tempered in a vacuum with a residual gas pressure of 4.10 ^-2 Pa at 1,610 ° C for 12 hours, then in pure oxygen at 0.12 MPa at 1,550 ° C. C for 8 hours and finally in a vacuum with a residual gas pressure of 2.10 “ ² Pa at a temperature of 1,280 ° C for 20 hours. Laser rods were made from tempered prisms, which when pumping energies of 100 J in the laser halves and a pulse frequency of 80 Hz had an output energy of 3.1 + 0.3 J. Rods made of prisms tempered by any other procedure showed in the pulsed laser an output energy of ^ 27% lower, while at a pulse frequency of 1-2 Hz, for example, they showed prismatic rods! tempered only in a vacuum at a temperature of 1,610 ° C the same laser properties as prism bars tempered successively in a vacuum, oxygen and a vacuum at a reduced temperature.

Claims (1)

OBJECT OF THE INVENTION Process for the preparation of neodymium ion-activated yttritoaluminum perovskite for high average power lasers, characterized in that the single crystals are grown by drawing from a melt under an atmosphere containing free hydrogen at a partial pressure of 10 to 10 Pa, then tempered in a vacuum with a residual gas pressure of less than 0.1 Pa at a temperature of 1,500 to 1,800 ° C for 2 to 18 hours, then in an atmosphere containing free oxygen with a partial pressure of 10 ⁴ to 10 $ Pa at a temperature of 1,400 to 1,700 ° C for 5 to 24 hours and finally in a vacuum with a residual gas pressure of less than 0.1 Pa at a temperature of 1,100 to 1,450 ° C for 3 to 25 hours.