Optical and Judd‐Ofelt spectroscopic study of Er³⁺‐doped strontium gadolinium gallium garnet single‐crystal

Abstract

Er3+‐doped strontium gadolinium gallium garnet (SrGdGa3O7) single‐crystal was grown by Czochralski method. The Er3+ concentration in the crystal was determined as 4.2 × 1021 ions/cm3 by inductively coupled plasma atomic absorption spectroscopy. Refractive index of the crystal was measured at the wavelengths of 633, 1311 and 1553 nm by prism coupling technique. The results show that the crystal is a positive uniaxial crystal with a birefringence of ~0.01, and the Sellmeier equation reported previously for the crystal doped with Nd3+ is also valid for the one doped with Er3+. Unpolarized absorption spectrum of the crystal was measured at room temperature and the Er3+ absorption cross‐section spectrum was calibrated from it. The Er3+ spectroscopic properties were studied by Judd‐Ofelt theory. Some fundamental spectroscopic parameters were obtained that include absorption coefficient and cross‐section spectral distributions, electronic transition oscillator strength, Judd‐Ofelt parameters, fluorescence branch ratio, transition probability, radiative and fluorescence lifetimes, and quantum efficiency.

Complement to “Optical and Judd‐Ofelt spectroscopic study of Er3+‐doped strontium gadolinium gallium garnet single‐crystal”

“…Instead, the corrected cross section has the values only slightly smaller than those reported in Ref. This is because the corrected Er 3+ absorption and concentration all are one order of magnitude smaller. For reader's convenience, in left part of Table we bring together the values of corrected integrated absorption coefficient Γ, barycenter wavelength , as well as the peaking cross‐section σ a at each unpolarized band.…”

“…Inductively coupled plasma atomic emission spectrometry re‐measurement shows that the Er 3+ concentration in the crystal should be N Er = 4.79 × 10 20 ions/cm 3 with a relative error ± 10% instead of 42 × 10 20 ions/cm 3 reported in the previous paper …”

“…Previous study has shown that the Er 3+ absorption in the studied crystal is extraordinarily large . For the two strongest transitions of 380 and 520 nm of Er 3+ , the peak absorption is as much as ~80 cm −1 .…”

“…Due to lower cut‐off phonon energy (~680 cm −1 ), highly disordered structure and longer lifetime (~0.7 ms) of the 4 I 11/2 (980 nm) manifold of Er 3+ active ions, strontium gadolinium gallate (SrGdGa 3 O 7 ) single‐crystal is not only an excellent laser host material but also a promising luminescent material for optical thermometry . In the previous paper, we have reported Judd‐Ofelt spectroscopic properties of Er 3+ ‐doped SrGdGa 3 O 7 single‐crystal, and the Judd‐Ofelt analysis was performed on the basis of unpolarized absorption spectrum of the crystal and the Er 3+ absorption cross‐section spectrum was calibrated from it . However, previous paper reported incorrect absorption spectrum and Er 3+ concentration in the crystal, which thus result in inaccurate Judd‐Ofelt spectroscopic data.…”

“…Moreover, the name of the host crystal studied is “strontium gadolinium gallate” instead of “strontium gadolinium gallium garnet” called in Ref. because it has the Melilite structure and is actually a gallate not a garnet. In addition, polarization‐resolved absorption spectra were measured and polarization effect was considered in the Judd‐Ofelt analysis.…”