CLNGG Crystal Research Articles

Buried Depressed-Cladding Waveguides Inscribed in Nd3+ and Yb3+ Doped CLNGG Laser Crystals by Picosecond-Laser Beam Writing.

Buried depressed-cladding waveguides were fabricated in 0.7-at.% Nd:Ca3Li0.275Nb1.775Ga2.95O12 (Nd:CLNGG) and 7.28-at.% Yb:CLNGG disordered laser crystals grown by Czochralski method. Circular waveguides with 100 μm diameters were inscribed in both crystals with picosecond (ps) laser pulses at 532 nm of 0.15 μJ energy at 500 kHz repetition rate. A line-by-line writing technique at 1 mm/s scanning speed was used. Laser emission at 1.06 μm (with 0.35 mJ pulse energy) and at 1.03 μm (with 0.16 mJ pulse energy) was obtained from the waveguide inscribed in Nd:CLNGG and Yb:CLNGG, respectively, employing quasi-continuous wave pumping with fiber-coupled diode lasers. The waveguide realized in RE3+-doped CLNGG crystals using ps-laser pulses at high repetition rates could provide Q-switched or mode-locked miniaturized lasers for a large number of photonic applications.

Proton-implanted waveguides in neodymium-doped calcium lithium niobium gallium garnet crystals

In this work, the 400-keV proton implantation with a fluence of 8 × 1016 ions/cm2 was employed to form a planar waveguide in the Nd: CLNGG crystal. The distributions of the energy loss and the refractive index profile were simulated by the SRIM 2013 and the RCM, respectively. The m-line curve and the near-filed intensity distribution were measured by the prism coupling technique and the end face coupling method, respectively. The proton-implanted Nd: CLNGG crystal waveguide with well-confined propagation can serve as an active integrated element.

Spectroscopic, thermal, and laser properties of disordered garnet Nd:CLTGG crystal

A large single crystal of Nd3+-doped calcium lithium tantalum gallium garnet (CLTGG) was successfully grown by Czochralski method. The effective distribution coefficient of Nd3+ was measured as 2.01. A series of thermal properties was systematically tested, and the Nd:CLTGG crystals exhibited superior thermal properties over those of Nd:CLNGG crystals. The emission and absorption spectra were obtained at room temperature. The FWHM (Full Width Half Maximum) of the absorption peak at 808 nm was 18 nm, and the emission peak at 1060 nm was 20 nm. The fluorescence lifetime, absorption coefficient, and other spectral parameters were calculated by J-O theory. In addition, the CW laser performance at a wavelength of 1.06 um was measured at room temperature. The slope and light conversion efficiencies were 17.8% and 16.3%, and the maximum output power was 1.32 W. These results revealed that Nd:CLTGG is promising high-performance laser crystal.

Crystal growth and structural characterization of Sm3+, Pr3+ and Dy3+-doped CNGG and CLNGG single crystals

Sm3+, Pr3+ and Dy3+-doped Ca3Nb1.6875Ga3.1875O12 - CNGG and Ca3Li0.275Nb1.775Ga2.95O12 - CLNGG crystals are of interest as solid-state laser materials emitting in the yellow-orange spectral range, especially for diode pumping due to their partially disordered nature. In this work, for the first time to our knowledge, single crystals of Sm, Pr and Dy-doped CNGG and CLNGG crystals were grown by the Czochralski method. For the doping of CNGG and CLNGG crystals, five new stoichiometric garnets were synthesised by solid-state reaction method: praseodymium-gallium-garnet (PrGG), dysprosium-gallium-garnet (DyGG) and praseodymium-lithium-niobium-gallium-garnet (PrLNGG), samarium-lithium-niobium-gallium-garnet (SmLNGG), and dysprosium-lithium-niobium-gallium-garnet (DyLNGG). Samarium-gallium-garnet (SmGG) was also sintered and used for the doping of Sm:CNGG crystal. Structural properties of sintered materials and grown crystals were investigated by X-ray diffraction and the chemical compositions of the grown crystals were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES) method. The spectroscopic investigations of the grown crystals have shown that they are promising laser materials in the yellow-orange spectral range.

Ca2.90Li0.30Nb1.93Ga2.76O12 and La0.57Ca2.38Li0.72Nb2.01Ga2.26O12 crystals: New substrates with more perfect lattice constant for garnet-type film

Two new substrate crystals, Ca2.90Li0.30Nb1.93Ga2.76O12 (CLNGG) and La0.57Ca2.38Li0.72Nb2.01Ga2.26O12 (LCLNGG), were successfully grown by the Czochralski method. Compared with Gd3Ga5O12 crystal, CLNGG and LCLNGG crystals possess the lattice constants better matched with those of highly Bi- or Ce-doped YIG films that have been widely used in the magneto-optical devices. The high quality and performance films are expected to be obtained by using CLNGG or LCLNGG as substrate material. In this paper, the structures of CLNGG and LCLNGG are refined by the Rietveld method, and the influences of doping on the crystal structure, transmittance, electrical conductivity, thermal expansion coefficient are discussed. Then, the causes of crystal defects are analyzed in detail. The results show that the lattice-matched seed and the atmosphere containing suitable oxygen partial pressure are crucial to obtain high-quality CLNGG crystal without crack and inclusion defects. Since the oxygen-vacancy defects are effectively reduced by doping Li+, Nb5+, and La3+ ions, LCLNGG crystal has a more perfect crystal structure, fewer vacancy defects and dislocation defects than CLNGG crystal.

The Laser Action of a Yb:CLNGG Crystal with an Efficiency Approaching Its Quantum Defect Imposed Limit

Continuous-wave laser operation is demonstrated at room temperature with a new disordered Yb:CLNGG crystal. A maximum output power of 5.05 W is generated with 7.8 W of pump power absorbed in the crystal, resulting in an optical-to-optical efficiency of 65%, whereas the slope efficiency is determined to be 92%, approaching the limit imposed by the quantum defect in the laser emission process.

Diode-pumped quasi-three-level Nd:CLNGG laser at 928 nm

We describe the output performances of the 928 nm 4 F 3/2 → 4 I 9/2 transition in Nd:CLNGG under diode-laser pumping. An end-pumped Nd:CLNGG crystal yielded 1.3 W of continuous-wave output power for 17.8 W of absorbed pump power. The slope efficiency with respect to the absorbed pump power was 11.2%. Furthermore, with 17.8 W of diode pump power and the frequency-doubling crystal LiB3O5 (LBO), a maximum output power of 260 mW in the blue spectral range at 464 nm has been achieved. The blue output power stability over 4 h is better than 3.2%.

Continuous-wave and passively Q-switched laser performance with a disordered Nd:CLNGG crystal

We demonstrated efficient high-power continuous-wave (cw) and passively Q-switched disordered Nd:CLNGG laser performance. In cw operations, the output power was obtained to be 3.81 W with a slope efficiency of 30.3%. To our knowledge, they are the highest cw power and efficiency with Nd:CLNGG as the gain medium and a laser-diode (LD) as the pump source. Recorded with a spectrum analyzer, no splitting was found in the Nd:CLNGG laser, which is different with that of its isomorph Nd:CNGG. The LD pumped passively Q-switched Nd:CLNGG laser was obtained for the first time to our knowledge. The shortest pulse width, largest pulse energy and highest peak power were achieved to be 12.3 ns, 199.1 microJ and 16 kW, respectively, with Cr(4+):YAG crystals as the saturable absorbers.

Congruency and morphology of Ca 3(LiNbGa) 5O 12 garnet crystals grown by Czochralski method

There is a strong demand for the garnet substrate with a large lattice parameter when high Bi-containing iron garnet films are deposited for magneto-optic devices. Ca 3Li 0.275Nb 1.775Ga 2.95O 12 (CLNGG) crystal is one of the promising substrates. The CLNGG crystal with the size of Ø20 mm×80 mm has been successfully grown by the Czochralski method. The grown crystal is transparent, bubble free, and scattering free. The growth ridges and facets are indexed by projection analysis and X-ray diffraction (XRD) methods. No variation is observed in the lattice parameter by the powder XRD experiments on different parts of grown CLNGG crystals. It indicates that the CLNGG crystal with the above composition is congruent.

Preparation, growth, and characterisation of Nd 3+-doped calcium lithium niobium gallium garnet (Nd 3+ : CLNGG) single crystals

Pure and Nd 3+-doped Ca 3Li 0.275Nb 1.775Ga 2.95O 12 (CLNGG) single crystals were grown by the Czochralski pulling technique. A new garnet, neodymium lithium niobium gallium garnet (NLNGG), was synthesised by solid-state reaction technique and, to keep charge balance, Nd 3Li 0.275Nb 0.275Ga 4.45O 12 composition was selected. CLNGG and NLNGG were found to have almost equal lattice parameters, therefore Nd 3+-doped CLNGG crystals were obtained by mixing and melting these two garnets. The growth conditions, crystal quality and preliminary spectroscopic properties of the Nd 3+-doped CLNGG are reported. The Nd 3+-doped CLNGG single crystals have broad absorption bands which are attractive for diode-pumped lasers.

Efficient active media based on Nd3+-activated calcium niobium gallium garnets

A spectroscopic investigation was made of Nd3+-activated crystals of calcium niobium gallium (CNGG) and calcium lithium niobium gallium (CLNGG) garnets. The energy parameters of active elements made of these crystals were determined for the first time. The absolute efficiency of a CNGG:Nd3+ crystal was 3.5%, higher than the efficiency (2.7%) of a YAG:Nd3+ crystal of high optical quality. The average output power obtained at a pulse repetition frequency of 50 Hz for a CLNGG crystal was 40 W and the efficiency was 2.7% for an active element 6 mm in diameter and 80 mm long. A comparison of the lasing characteristics of CNGG:Nd3+ and CLNGG:Nd3+ crystals revealed a considerable superiority of the latter in respect of several parameters: the damage threshold (which was twice as high), the divergence, and the influence of a thermal lens at high pump powers. Room-temperature lasing of CNGG:Nd3+ and CLNGG:Nd3+ crystals was observed as a result of the 4F3/2 ← 4I11/2 transition at three wavelengths: 1059.3, 1061.5, and 1066 nm.