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Abstract: Secondary ion mass spectrometry (SIMS) was used to study the diffusion properties of Mg2+ and Ti4+ ions in a peculiar optical-damage-resistant near-stoichiometric (NS) Ti:Mg:LiNbO3 waveguide structure that a number of strip waveguides are embedded in a planar waveguide. The structure was fabricated on an initially congruent, undoped Z-cut substrate with a technological process in sequence of planar waveguide, strip waveguide, MgO diffusion and post Li-rich vapor transport equilibration (VTE) treatment. The results show that the Mg2+-profiles in both strip and planar waveguide layers are desirably homogeneous with a concentration 1.7±0.3mol% above the optical damage concentration threshold. The Ti4+-profile in the strip waveguide follows a sum of two error functions along the lateral direction with a width 13±1.0μm and a sum of two Gaussian functions in the depth direction with a 1/e depth of ∼11μm all. The Ti4+ ions in the planar waveguide obey a Gaussian profile. From the measured profiles, characteristic diffusion parameters such as mean Mg2+ and Ti4+ diffusivities and surface Ti4+-concentration are evaluated. The diffusivity is discussed in comparison with the previously reported results on single Mg2+, Ti4+ diffusion and Mg2+/Ti4+ co-diffusion in pure (or bulk MgO-doped), congruent (or NS) LiNbO3 crystal. Finally, the keys to the succeeding in fabrication are highlighted. [Copyright &y& Elsevier]

Abstract: The emission and absorption spectra of Er3+ ions in Er2O3 powder are investigated at room temperature. The crystal field splitting of 4I15/2, 4I13/2, 4I9/2 and 4S3/2 multiplets of Er3+ was calculated using a parameterized Hamiltonian including crystal field terms. A final standard deviation of 5.3cm−1 is obtained between 22 calculated and experimental Stark. The strength crystal field parameters of Er2O3 powder are compared to those of erbium doped Y2O3 single crystal. In addition, the location of the ground and the first excited states of Er3+ in Er2O3 powder is determined. The 4I15/2 ground state of Er3+ is located at 12750cm−1 below the valence band edge. The 4I13/2 and 4I11/2 multiplets are set in resonance with the valence band. A configuration coordinate diagram is proposed for Er3+ in Er2O3 powder. [Copyright &y& Elsevier]

The formation of ErNbO4 powder, prepared by calcining an Er2O3 (50 mol%) and Nb2O5 (50 mol%) powder mixture at 1100 and 1600 °C for different durations, was investigated by using X-ray diffraction. The experimental results have displayed that although the solid-state reaction had started to some extent when the mixture was pre-calcined at 1100 °C for a duration of 13 h, the two original phases Er2O3 and Nb2O5 still dominated the mixture. When the duration of the calcination reaction was increased to 120 h at the same temperature, the resultant mixture experienced a nearly complete phase transformation. Accordingly, the ErNbO4 phase was dominant phase in the mixture. Nevertheless, a small portion of the raw powder still existed in the mixture. When the calcining temperature was elevated to 1600 °C, ErNbO4 powder with higher purity could be obtained for a relatively much shorter duration (only up to several tens of hours). A simple formation mechanism of ErNbO4, an elevated-temperature-assisted solid-state chemical reaction: Er2O3+Nb2O5⇌2ErNbO4, is suggested. In addition, the present experimental results offer important evidence for the formation of the additional phase ErNbO4 induced in Er:LiNbO3 crystals by vapour transport equilibration (VTE) treatment. [Copyright &y& Elsevier]

Abstract Optical and spectroscopic properties of Er3+/Pr3+-codoped Gd 3 Ga 5 O 12 single-crystal grown by Czochralski method have been studied. Absorption spectrum of the crystal was measured at room temperature and Er3+ absorption cross-section spectral distributions were calibrated from it. The Er3+ spectroscopic properties were analyzed on the basis of the Judd-Ofelt theory. Fundamental spectroscopic parameters were obtained that include absorption coefficient, cross-section spectral distribution, electronic transition oscillator strength, Judd-Ofelt parameters, fluorescence branch ratio, transition probability, radiative and fluorescence lifetimes, and quantum efficiency as well. Study shows that Pr3+-codoping results in substantial change of Er3+ spectroscopic properties, in qualitative consistent with the previous fluorescence studying result. In addition, refractive index of the crystal was measured at different wavelengths using prism coupling method, and the Sellmeier equation reported previously for Er3+-only doped Gd 3 Ga 5 O 12 crystal is corrected. Highlights • Juud-Ofelt spectroscopic properties of Er3+/Pr3+:Gd 3 Ga 5 O 12 crystal were studied. • Pr codoping results in substantial increase of the Judd-Ofelt parameters. • Pr codoping induces shortening of Er3+ 2.7 and 1.5 μm lifetimes from ms to sub-ms. • The effect is related to two resonant energy transfers from Er3+ to Pr3+. • Different efficiencies of the two transfers enable to realize 2.7 μm lasing. [ABSTRACT FROM AUTHOR]

Abstract Gallium-diffused lithium niobate (LiNbO 3) channel optical thin-film was fabricated by diffusion of photolithographically patterned gallium-oxide stripes on a Z-cut congruent LiNbO 3 substrate. Composition, optical properties of the channel thin-film and gallium diffusion profiles were characterized. The results show that the thin-film is in congruent composition environment, confines single-mode ordinary and extraordinary waves with a loss <0.5 dB/cm at 1.5 μm wavelength. The confined mode field follows Gaussian/Hermite-Gaussian profile in the width/depth direction of the channel thin-film, and shows definite anisotropy. The diffused gallium ions follow a sum of two error functions in the width and a Gaussian function in the depth direction of the channel optical thin-film. Two-dimensional gallium concentration and refractive index profiles in the channel thin-film are modeled. [ABSTRACT FROM AUTHOR]

Under 980 nm wavelength excitation, green upconversion emission spectra of Er 3+ ions in NaYF 4 (NYF) micro-crystals were measured in the temperature range of 298–383 K. A multiple ratiometric thermometry is proposed to realize reliable temperature sensing. It considers six luminescence intensity ratios(LIRs) involving two peaks at 530 nm emission band and three peaks at 550 nm emission band, which concern electronic transitions between crystal-field Stark sublevels of Er 3+ . The six LIR schemes display similar temperature characteristics with high thermometric efficiency. The temperature can be overall determined by the six LIR schemes, largely increasing measurement reliability. The study also shows that the 980 nm excitation power adopted neither induces a detectable temperature change nor has a noticeable effect on the LIR value. In addition, the Er 3+ -doped NYF phosphor displays intense green emissions and thermally stable spectral structure which are desired for the multiple ratiometric thermometry. [ABSTRACT FROM AUTHOR]

Ti-diffused LiTaO 3 strip waveguide was fabricated by in-diffusion of 8-μm-wide, 100-nm-thick Ti-strip at 1300 °C for 6 h in wet O 2 atmosphere. Its composition, surface morphology, lattice parameter, optical properties and Ti profile characteristics were fully characterized. It is shown that the waveguide is in the congruent composition environment. The waveguide surface caves in ∼70 nm below the crystal surface due to Ti-induced lattice contraction, which is verified by X-ray single-crystal diffraction. Optical characterizations show that the waveguide well supports both TE and TM single-mode propagation at the 1.5 μm wavelength, is polarization-insensitive, and has a loss of 0.4 (0.3) dB/cm for the TM (TE) mode. Secondary ion mass spectrometry analysis shows that the Ti profile follows a sum of two error functions in the width direction and a Gaussian function in the depth direction of the waveguide. [ABSTRACT FROM AUTHOR]

Abstract: Diffusivity of Li+ in 5mol% (in growth melt) MgO-doped LiNbO3 crystal has been studied as a function of Li2O-content ranging from 43.4 to 44.4mol% under different temperatures. First, diffusion-limited Li2O-content depth profiles were produced by carrying out Li-poor vapour transport equilibration (VTE) treatments on two 0.5-mm-thick MgO-doped LiNbO3 plates at 1100 and 1130°C for 40h. Second, the profiles were obtained by alternatively doing the optical polish to one crystal surface and the Li2O-content characterization on the polished surface through the measurement of birefringence. Third, Boltzmann–Matano method was applied to the profile to derive the Li+ diffusivity as a function of Li2O-content. The results show that the diffusivity decreases with the reduced Li2O-content by at least two orders of magnitude as the Li2O-content reduces by 1mol% from the as-grown state. In the Li2O-content range studied, the diffusivity at 1130°C is at least two times larger than that at 1100°C. In addition, we also studied the time dependence of the Li-poor-VTE-induced reduction of Li2O-content on surface of the same MgO-doped crystal. The results show that the surface Li2O-content reduction induced has a square-root dependence on the VTE duration. Based upon this dependence, the mathematical solution to the Li+ diffusion equation, an integral of error function complement, is obtained and verified by the experimental result. It is concluded that the MgO doping has less effect on both the Li+ diffusivity and the dependence of surface Li2O-content reduction on the VTE duration. [Copyright &y& Elsevier]

In the previous paper [J. Alloys Compd. 102 (2019) 873–878], optical and Judd-Ofelt (J-O) spectroscopic properties of Er3+/Pr3+-codoped Gd 3 Ga 5 O 12 single-crystal have been reported and the J-O study was performed on the basis of measured absorption spectrum of the crystal. Present paper reports corrected absorption spectrum and J-O spectroscopic parameters of the crystal, which include J-O intensity parameters, oscillator strengths, fluorescence branch ratios, radiative rates and radiative lifetimes. Comparison shows that the previous paper erroneously reported almost one order of magnitude larger absorption cross-section, J-O intensity parameters, oscillator strength and radiative rate as well. A further comparison with previously reported results of Er3+-only doped crystal reveals that the Pr3+-codoping causes considerable spectroscopic change in absorption cross-section, J-O intensity parameters, oscillator strength and radiative rate of Er3+ transitions, and the reason of the change is discussed from the viewpoint of Pr3+-codoping and crystal growth procedure effect on ion environment of Er3+. In addition, errors are given for both the J-O parameters and radiative probabilities of several typical Er3+ emissions. [ABSTRACT FROM AUTHOR]