Laser Properties of Sapphire Crystals

Laser Properties of Sapphire Crystals

Annealing of irradiated RE leads to reincorporation of irradiated defects. Recovery even after short-term phototreatment of Ep.

The strength of induced adsorption can be reduced or lowered by the introduction of vanadium or titanium. Titanium acts as a protector only in crystals annealed in vacuum or reducing atmosphere.

Ti:(Al2O3) is one of the best activation media for tunable lasers.

The d-element is characterized by a strong interaction with unfilled d-shells of crystal field ions, which leads to broadening of the absorption and emission bands. The broad emission band is used to tune the laser emission frequency and the spectrum of titanium is one of the broadest. Different For ruby, the cleavage schematic of the titanium standard does not contain the absorption in the pumping and generating regions.

For Ti:Al2O3-based lasers, efficiencies comparable to or exceeding those of fuel lasers in the 0.7-0.9 μm range have been achieved. This class of crystals has high laser resistance. Attenuation at 4 ns with 0.532 nm wavelength and tp=10 ns radiation Occurs at an energy density of -5 J/cm2. The production characteristics of Ti:Al2O3 are listed in Table 1.12.

For pumping, the absorption band corresponding to the blue-green region of the main transition 2T2g→2Eg was used. The strongest absorption band is located in the UV region. This region contains the first excited 2S order of free Ti3+ ions, corresponding to the 4S1 structure, where the absorption is equal to The intrinsic absorption of the matrix overlaps. The d→s transition, corresponding to the splitting of parity and spin, is consistent with charge transfer.

In the generation region the absorption is determined by the Ti content and reaches 0.15 cm-1, ~10% of the absorption is at the main line maximum. The excitation of Ti:Al2O3 in the UV region is accompanied by luminescence, with maximum values at 0.25 and 0.315 μm . The crystal has a wide luminescence band in the 0.6-1.1μm region (Fig. 2.82).

In comparison with the absorption spectrum, the luminescence spectrum shows a clear distinction between the emission intensities of the different polarizations: the intensity of the π polarization (E‖C) is almost three times higher than that of the σ polarization. The emission band is Inhomogeneous and has a maximum value in the range of 0.79-0.80 μm. The luminescence quantum yield is 0.81-1.0 at 300K, and the lifetime is 3.9-2.6 ms.

Figure 2.82 Absorption and luminescence spectra of Ti:Al2O3

In addition to the emission band in the IR region, an emission band overlapping with the visible region is also observed. The overall emission spectrum of Ti:Al2O3 includes a Ti3+IR emission band with a peak at ~0.78 μm and a Ti3+ IR emission band at ~0.42 μm An additional luminescence band in the short-wavelength band of the peak. With 0.532 μm wavelength · high-energy radiation pumping, the luminescence lifetime is 4.0 ms for the 0.78 μm band. Its growth is related to the luminescence pumping in the blue-green region (~0.42 μm). The lifetime in the short-wave band is 7.4 ms, and the lifetime in the 0.42 μm light-emitting band is 2.3 ms.

Two additional luminescence lines are found on UV pumping: a polarization line with a peak at ~0.425 μm and a π polarization line with a peak at ~0.575 μm. The latter has a lifetime of 2.1 ms.

The spectral properties of the two laser media are determined by the oxidation-reduction potential of the annealing atmosphere. For Ti:Al2O3 based femtosecond high-energy lasers (pico and terawatt), acousto-optic programmed filters, pulse compressors and other wavefront and pulse shape improvements The method has been described in detail.

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