Calcium Niobium Gallium Garnet Crystal Research Articles

Spectroscopy of Yb3+,Ho3+,Eu3+-codoped calcium niobium gallium garnet (CNGG) crystal

Calcium niobium gallium garnet (CNGG) crystals codoped with Yb3+, Ho3+ and Eu3+ ions were grown by the Czochralski method. The crystal structure (cubic, sp. gr. O10h - Ia3d, lattice constant a = 12.4748(2) Å) was refined by the Rietveld method. A Raman study revealed high-energy vibrations at 767–846 cm−1 due to the [Nb2|Ga2O4] groups. The spectroscopic properties of Yb,Ho: and Yb,Ho,Eu:CNGG crystals were studied with the goal of developing broadband emitting gain media around 2 μm and 3 μm. The maximum stimulated-emission cross-sections σSE are 0.57 × 10−20 cm2 at 2070 nm (the 5I7 → 5I8 Ho3+ transition) and 1.01 × 10−20 cm2 at 2869 nm (the 5I6 → 5I7 Ho3+ transition) and the emission spectra are smooth and broad owing to the structural disorder of the CNGG host matrix. The evidence of Yb3+(2F5/2) → Ho3+(5I6) energy transfer (ET) in the Yb,Ho:CNGG crystal is shown. Without Eu3+, the luminescence lifetimes of the 5I6 and 5I7 Ho3+ states are 0.30 ms and 7.24 ms, respectively. The Eu3+ codoping leads to the quenching of the 5I7 Ho3+ lifetime due to the Ho3+(5I7) → Eu3+(7F6) ET which is favorable for 3 μm laser operation. The crystal-field splitting of the Ho3+ multiplets is revealed at 12 K. First laser operation in Yb,Ho:CNGG crystals at 2.1 μm is achieved.

Planar waveguides in neodymium-doped calcium niobium gallium garnet crystals produced by proton implantation**Project supported by the National Natural Science Foundation of China (Grant Nos. 11405041, 61405240, 61077070, 61177086, 51002181, and 61177084), the Scientific Research Starting Foundation for New Teachers of Nanjing University of Posts and Telecommunications (NUPTSF) (Grant No. NY214159), and the Research Center of Optical Communications Engineering & Technology,

In this work, the fabrication and optical properties of a planar waveguide in a neodymium-doped calcium niobium gallium garnet (Nd:CNGG) crystal are reported. The waveguide is produced by proton (H+) implantation at 480 keV and a fluence of 1.0×1017 ions/cm2. The prism-coupling measurement is performed to obtain the dark mode of the waveguide at a wavelength of 632.8 nm. The reflectivity calculation method (RCM) is used to reconstruct the refractive index profile. The finite-difference beam propagation method (FD-BPM) is employed to calculate the guided mode profile of the waveguide. The stopping and range of ions in matter 2010 (SRIM 2010) code is used to simulate the damage profile induced by the ion implantation. The experimental and theoretical results indicate that the waveguide can confine the light propagation.

Interaction of Er3+ ions in Er-doped calcium — niobium — gallium garnet crystals

The processes of nonradiative energy transfer in calcium — niobium — gallium garnet (CNGG) crystals doped with Er3+ ions are studied. It is found that the energy of erbium ions in the Er:CNGG crystal with the erbium atomic concentrations CEr=6% and 11% is transferred via the nonradiative co-operative processes 4I11/2→ 4I15/2, 4I11/2→ 4F7/2, 4I11/2→ 4I15/2, 4I13/2→ 4F9/2; and 4I13/2→ 4I15/2, 4I13/2→ 4I9/2, whose efficiency increases with increasing intensity of exciting radiation. It is shown that the cross-relaxation processes 4S3/2→4I9/2, 4I15/2→4I13/2, whose intensity depends on the concentration of Er3+ ions, are characteristic for Er:CNGG crystals with the Er atomic concentration above 1%.

Intensity of the f-f transitions of Nd3+, Er3+, and Tm3+ rare-earth ions in calcium niobium gallium garnet crystals

This paper reports on the results of the investigation into the intensities of the f-f transitions of Nd3+, Er3+, and Tm3+ ions in calcium niobium gallium garnet (CNGG) crystals. The values of the oscillator strengths and line strengths obtained for hypersensitive transitions and the intensity parameters Ω t of the rare-earth ions in the CNGG crystals are compared with the corresponding quantities for crystals of other garnets and some oxide and fluoride crystals. The assumption is made that an increase in the oscillator strengths and line strengths for the hypersensitive transitions and the intensity parameters Ω2 of the Nd, Er, and Tm ions in the CNGG crystals as compared to those for crystals of other garnets is associated with the specific features revealed in the crystal structure of the calcium niobium gallium garnet, in particular, with the lowering of the symmetry of the positions occupied by rare-earth ions in the crystal structure.

Yb3+ ion in calcium niobium gallium garnet crystals: Nearest neighbor environment and optical spectra

We have studied inhomogeneously broadened optical spectra of the Yb3+ ion in calcium niobium gallium garnet crystals using selective laser excitation, time-resolved luminescence spectroscopy, and 2 F 5/2 luminescence decay measurements under excitation in different portions of the absorption spectrum. We have identified spectral features due to individual optical centers differing in excitation and luminescence wavelengths and excited-state lifetime. Tentative structures of the optical centers responsible for the inhomogeneous broadening of the spectra are described.

Continuous lasing at a 2 μm wavelengthin calcium niobium gallium garnet crystals at room temperature

Continuous lasing resulting in the emission of radiation of the 2.02 μm wavelengthwas achieved in Tm3+-activated calcium niobium gallium garnet crystals at room temperature. Lasing was observed when the Tm3+ ions were excited by Nd:YAG laser radiation with λ = 1.06 μm. The output radiation power was 0.02 W. Mechanisms of nonlinear absorption of the pump radiation were investigated.

Lasing and spectroscopic properties of calcium-niobium-gallium garnet crystals doped with Tm3+ ions

The lasing properties and luminescence spectra of calcium-niobium-gallium garnet (CNGG) crystals doped with Tm3+ ions have been studied. The efficiency of the cross-relaxation process in the CNGG crystals, βTm→Tm, was determined from integral characteristics of the luminescence decay curves of the Tm3+ ions. Stimulated emission at a wavelength of 2.02 μm with an output energy of 3.3 J in the pulse was achieved in Tm:CNGG crystals (on the 3F4→3H6 transition) at T=300 K.

Spectroscopic and lasing properties of calcium niobium gallium garnet activated with Tm3+and Cr3+ions

An investigation was made of spectroscopic and lasing properties of a calcium niobium gallium garnet crystal (CNGG) activated with Tm and Cr. A study was made of the kinetics of decay of the luminescence emitted by the Cr3+ ions. Efficient nonradiative transfer of energy from the Cr3+ to the Tm3+ ions was observed at room temperature. Stimulated radiation was generated in CNGG:Tm:Cr crystals (due to the 3F4→3H6 transition) under conditions of free running: the wavelength of this radiation was 2.02 μm at room temperature.

Lasing of a calcium niobium gallium garnet crystal activated with chromium and erbium (λ = 2.71 μm)

An investigation was made of the luminescence spectra and lasing parameters of a calcium niobium gallium garnet crystal activated with chromium and erbium. The lifetimes of the upper 4I11/2 and lower 4I13/2 active levels of the Er3+ ions were determined. The lasing parameters of the crystal (λlas = 2.71 μm) were determined under free-running conditions at room temperature.

Spectroscopic and lasing properties of calcium niobium gallium garnet activated with Cr3+and Nd3+

An investigation was made of the luminescence and lasing spectra of a calcium niobium gallium garnet crystal activated with Cr3+ and Nd3+ ions. An effective nonradiative energy transfer from the chromium to the neodymium ions was discovered. The probability of an elementary Cr→Nd interaction event was determined. A detailed study was made of the Stark structure of the ground (4I9/2) and metastable (4F3/2) levels of Nd3+. Selective laser excitation was used to identify four main optical Nd3+ centers for which the splitting schemes of the 4I9/2 and 4F3/2 levels were constructed. Lasing was observed at 300 K as a result of the 4F3/2→4I11/2 transition in crystals activated with Cr3+ and Nd3+.