Foto- és neutronrefraktív anyagok és jelenségek = Photo- and neutronrefractive materials and effects

A fotorefraktív kristályokban fény hatására kialakuló holografikus rácsok időbeli változásának vizsgálatára több módszert is kidolgoztunk, melyek fáziskontraszt és interferencia mikroszkópián, digitális holografikus interferencián, illetve egy négyhullámkeveréses topografikus elrendezésen alapulnak. Kimutattuk, hogy a fotorefraktív LiNbO3 kristályba írt rács diffrakciós hatásfoka termikus neutron-besugárzás hatására lecsökken, lehetőséget nyújtva neutron dozimetriai alkalmazásra. Spektroszkópiai méréseken alapuló módszereket dolgoztunk ki a LiNbO3 összetételének, sugárzással vagy termokémiai redukcióval létrehozott hibaszerkezetének és a fotorefraktív viselkedést befolyásoló adalékok és szennyezők koncentrációjának kristálybeli meghatározására. Röntgendiffrakciós, dielektromos, elektronmikroszkópos és optikai spektroszkópiai módszerekkel meghatároztuk számos lézer- és magneto-optikai alkalmazással rendelkező kristály összetétel- és adalékfüggő hibaszerkezetét, valamint periodikusan polarizált domén szerkezeteket, sík- és csatorna hullámvezetőket állítottunk elő és tanulmányoztunk mikroszkópos, Raman szórási és felületi profilometriai módszerekkel. | Several methods based on phase-contrast and interference microscopy, digital holographic interferometry, and a four-wave-mixing topographic setup have been elaborated for the investigation of the real-time development of light-induced holographic gratings in photorefractive crystals. It has been shown that the diffraction efficiency of the grating recorded in the photorefractive LiNbO3 crystal decreases under thermal neutron radiation which may be useful for neutron dosimetric application. Methods based on spectroscopic measurements have been elaborated to determine the composition, the defect structure induced by radiation or thermochemical treatment, and the concentration of dopants and impurities effecting the photorefractive behavior in LiNbO3 crystals. X-ray diffraction, dielectric, electron microscopic and optical spectroscopic methods have been used to determine the composition and dopant-dependent defect structure of several laser and magneto-optical crystals. Periodically polarized domain structures as well as planar and channel waveguides have been fabricated and investigated by optical microscopes, Raman scattering and surface profilometry

Photorefractive damage resistance threshold in stoichiometric LiNbO_3:Zr crystals

Several optical methods including ultraviolet absorption, infrared absorption of the hydroxyl ions, Raman spectroscopy, and the Z-scan method have been used to determine the damage resistance threshold in 0–0.72 mol. % Zr-containing, flux-grown, nearly stoichiometric LiNbO3 single crystals. All spectroscopical methods used indicate that samples containing at least ≈0.085 mol: % Zr in the crystal are above the threshold while Z-scan data locate the photorefractive damage threshold between 0.085 and 0.314 mol. % Zr

Saturation Spectroscopic Studies on Yb3+ and Er3+ Ions in Li6Y(BO3)3 Single Crystals

The results of a series of pump–probe spectral hole-burning experiments are presented on Yb3+- or Er3+-doped Li6Y(BO3)3 (LYB) single crystals in the temperature range of 2–14 K and 9–28 K, respectively. The spectral hole has a complex structure for Yb3+ with superposed narrow and broad bands, while a single absorption hole has been observed for Er3+. Population relaxation times (T1) at about 850 ± 60 μs and 1010 ± 50 μs and dipole relaxation times (T2) with values of 1100 ± 120 ns and 14.2 ± 0.3 ns have been obtained for the two components measured for the Yb3+:2F7/2—2F5/2 transition. T1 = 402 ± 8 μs and T2 = 11.9 ± 0.2 ns values have been found for the Er3+:4I15/2—4I11/2 excitation. The spectral diffusion rate at about 1 and 5 MHz/ms has been determined for the narrow and broad spectral line in Yb3+-doped crystal, respectively. The temperature dependence of the spectral hole halfwidth has also been investigated

Saturation Spectroscopic Studies on Yb³⁺ and Er³⁺ Ions in Li₆Y(BO₃)₃ Single Crystals

The results of a series of pump–probe spectral hole-burning experiments are presented on Yb3+- or Er3+-doped Li6Y(BO3)3 (LYB) single crystals in the temperature range of 2–14 K and 9–28 K, respectively. The spectral hole has a complex structure for Yb3+ with superposed narrow and broad bands, while a single absorption hole has been observed for Er3+. Population relaxation times (T1) at about 850 ± 60 μs and 1010 ± 50 μs and dipole relaxation times (T2) with values of 1100 ± 120 ns and 14.2 ± 0.3 ns have been obtained for the two components measured for the Yb3+:2F7/2—2F5/2 transition. T1 = 402 ± 8 μs and T2 = 11.9 ± 0.2 ns values have been found for the Er3+:4I15/2—4I11/2 excitation. The spectral diffusion rate at about 1 and 5 MHz/ms has been determined for the narrow and broad spectral line in Yb3+-doped crystal, respectively. The temperature dependence of the spectral hole halfwidth has also been investigated