Optical spectroscopy ofLa3Ga5

M. Casalboni

¹

,

A. Luci

²

,

U. M. Grassano

³

et al.

Abstract

The optical properties of trivalent chromium ions in La3Ga5SiO&4 crystals have been investigated by means of absorption, emission, excitation, and lifetime measurements. The particular intermediate value of the octahedral crystal field Dq/B 2.5 causes the overlapping of the Tz with the E and T~levels. This overlap is the origin of Fano resonances in the absorption spectrum and of the simultaneous presence of broadband and narrow-line emissions. Polarized measurements have allowed the determinations of second-order efFects such as the tetragonal or orthorhombic distortion of the octahedron of oxygen ions around the chromium ion. Moreover the temperature shift of the peak and the nonexponential decay of the broad emission band are indications of the disorder present in the crystal lattice. All these results produce a fairly complete picture of the energy levels of Cr + ions in a typical crystal of the Ca-gallogermanate family.ments and lasing performances on this system were already published. "' In this paper we present a new and more detailed study on the optical properties of Cr + ion in the La3Ga5SiOq4 crystal. In particular we have performed absorption, emission, excitation and lifetime measurements from which we derive a complete description of the Cr + energy levels.

Optical properties and site distribution of Cr3+ ions in alkali-disilicate glasses

“…The values obtained, given in Table 2, are similar to those obtained for other silicate glasses [25,30]. An increase of about 10% is observed from 13 K to RT indicating a slight temperaturedependent dynamic contribution and, consequently, a dominant static distortion that relaxes the forbidden transition [6].…”

“…For absorption, both bands are very similar. In the excitation spectra the high energy band intensity are lower than the lowenergy one, this effect has been observed in other glasses as fluorobromozirconates [32] and in crystals like Ca-gallogermanates [6] and has been associated to non-radiative de-excitations from the 4 T 1 ðt 2 2 eÞ state. The emission spectra mainly consist in a broad band centred at approximately 11,900 cm À1 (840 nm) corresponding to the 4 T 2 ðt 2 2 eÞ-4 A 2 ðt 3 2 Þ transition (see Fig.…”

“…In the same way, the sites emitting from the 2 E level, called highfield sites, are characterised by a narrow band in the upper limit of the visible range (around 690 nm) and a weak electron-lattice coupling. In most of the Cr 3+ -doped glasses [2][3][4][5] and in some crystalline structures [6,7] emission is dominated by low-field sites. This fact has attracted much attention in the development of laser gain media, because of the possibility of a wide tuning range for laser action.…”

Tuning into blue and red luminescence in dual-phase nano-glass–ceramics

“…The value of the local crystal-field parameter Dq is obtained from the mean peak energy of the 4 A 2 ? 4 T 2 transition [28]:…”

Linear Dichroism Spectra of Doped Calcium Gallogermanate Crystals

“…In the same time, one can note that the information about the peak position of these bands can be used to calculation of the magnitude of crystal field strength Dq, and Racah parameter B [12]. Moreover, in this case it has been found that the Dq ≈ 1584 cm −1 (0.197 eV), and B ≈ 684 cm −1 (0.085 eV).…”