摘要:

We have conducted a number of experiments in order to ascertain the temperature dependence of the rate of energy transfer between rare earth ions in solids. The mechanism of such dependence is peculiar to each donoracceptor pair. We report typical examples and point to some criteria that emerge from our studies.

ISSN:1042-0150    

DOI:10.1080/10420159508218780

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

We report new ultrafast color center lasers operating in the near infrared spectral range. Using newly developed KCl and KBr (F2+)Hand (F2+)AHcolor center systems and synchronous mode-locking we realize picosecond and subpicosecond color center laser operation for the first time in the 1.8–2.4 μm wavelength range. Using semiconductor saturable absorbers we passively mode-lock NaCl (F2+)Hand KCl FA(Tl) color center lasers in single- and coupled-cavity configurations. This results in mode-locked laser operation in the 1.5–1.7 μm range with shortest obtained transform-limited pulses of ∼ 150 femtosecond duration and pulse energies as high as several nJ. As a step toward infrared spectral continuum generation we amplify these nJ-level pulse energies by a factor of ∼ 103using KCl FA(Tl) amplifier crystals.

ISSN:1042-0150    

DOI:10.1080/10420159508218781

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

During irradiation of NaCl with ionizing radiation at moderate temperatures (50–150°C) irregular structures of very fine Na and Cl nano-precipitates are formed. The increase of the temperature to a value between 50 and 250°C might induce explosive reactions between radiolytic Na and Cl in heavily irradiated NaCl, which are accompanied by a loss of stored energy up to 30%. The reactions produce a very fast local temperature rise of at least 800°C and are accompanied by thermal shock waves. Due to explosive reactions the crystals desintegrated into many small frágments. Experiments and theoretical calculations have been carried out to study heavily irradiated NaCl and the dynamics of the thermal shock wave.

ISSN:1042-0150    

DOI:10.1080/10420159508218782

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The possibility of use of cathodoluminescence imaging in a scanning electron microscope as a method for characterization of quality of laser crystals and control of crystal growth technology is discussed. The room temperature measurements reveal a large variety of defects and non-uniformities such as striations, facets, inclusions, spiral dislocations and so on in important laser crystals such as YAG:Nd or YAG:Tm, Cr. Various mechanisms leading to differences in emission intensity such as the concentration effect and cross-relaxation or the influence of stress on the efficiency of energy transfer between the bound exciton and the rare-earth activator are discussed.

ISSN:1042-0150    

DOI:10.1080/10420159508218783

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The excited state absorption (ESA) from the metastable level4T1(4G) of Fe3+in tetrahedral sites of garnets is reported. The spectra show strong lines due to spin allowed transitions to other excited spin-quartet states. It is also shown that this ESA could be strongly reduced if the metastable level could is used as donor level in the process of sensitaization of rare earths ions (such as Tm3+) by Fe3+.

ISSN:1042-0150    

DOI:10.1080/10420159508218784

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The temperature dependence of the main energy transfer processes involved in the building of population inversion in 3 μm Erbium lasers, mainly upconversion from4I13/2,4I11/2, and cross-relaxation from4I9/2, is investigated. In the temperature domain 20–100°C, which includes the usual working temperatures of solid-state lasers, the change of the quantum efficiency is mainly due to the modifications of the Stark sublevels populations involved in laser transitions. The contribution of the cross-relaxation from4I9/2is estimated using new experimental data for two Erbium-doped crystals: Er3+: YAIO3and Er3+: YLiF4.

ISSN:1042-0150    

DOI:10.1080/10420159508218785

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Luminescence of Mn2+in A sites in natural and synthetic MgAl2O4spinel has been studied. In the near perfect structure of the natural crystals the degenerate levels of the Mn2+are splitted due to a symmetry lower than tetrahedral. In synthetic crystals the structure of the spectra is lost as a consequence of the superposition of partial spectra related to Mn2+ions perturbed by the cationic disorder of the lattice. Thermal annealing modifies the spectra of natural crystals making them similar to those of the synthetic ones due to an order-disorder transition.

ISSN:1042-0150    

DOI:10.1080/10420159508218786

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The optical absorption spectrum of CaYAIO4single crystals codoped V4+and Mg2+comprised two intense bands at 330 nm and 430 nm and a weak band around 500 nm. Excitation with light at wavelength near 500 nm produced a broad emission band with the peak at 690 nm. The radiative center is assigned to V4+. The peak wavelength of this emission band shifted to longer wavelength with increasing the excitation wavelength. This result indicates that inhomogeneous broadening of the V4+luminescence is caused by substitutional disorder on the Ca2+and Y3+sites in the host lattice.

ISSN:1042-0150    

DOI:10.1080/10420159508218787

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The paper presents new results on Nd3+multisite structure in high-temperature grown YAG crystals, obtained by high resolution spectroscopy. The energy transfer processes involving various satellites are also analyzed. Models of crystals field perturbations leading to the spectral satellites are discussed.

ISSN:1042-0150    

DOI:10.1080/10420159508218788

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

This paper reports the top-seeded high temperature solution growth (TSSG) of large single crystals of Cr3+-doped YAl3(BO3)4. Optical absorption measurements at T = 300 K reveal broad bands associated with transitions from the4A2ground state of Cr3+to the4T2and4T1excited states. The doublet R-lines and their one-phonon sideband are clearly resolved at room temperature in both absorption and luminescence spectra: the splitting of the R-lines demonstrates the effect of the even-parily trigonal distortions of their environment on the4A2and2E-levels of the Cr3+ions.

ISSN:1042-0150    

DOI:10.1080/10420159508218789

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor