CNGS Crystal Research Articles

Photoelasticity of CNGS crystals.

All piezo-optic coefficients (POCs) and elasto-optic coefficients (ELOCs) of C a 3 N b G a 3 S i 2 O 14 (CNGS) and C a 3 T a G a 3 S i 2 O 14 (CTGS) trigonal crystals of the langasite group are determined from quantum mechanical calculations based on the hybrid density functional theory, as implemented in the CRYSTAL program. The calculation results for CTGS crystals are compared with experimental data. Indicative surfaces of piezo- and elasto-optic effects are constructed based on the POC and ELOC matrices of CNGS crystals and the largest values of these effects are determined. The maximum values of the coefficient of the acousto-optic figure of merit M 2 of the CNGS crystal are determined for the geometries of elasto-optic interaction, which correspond to the maxima of the elasto-optic effect. These results are compared to the corresponding results for CTGS and langasite crystals. The spectral dependence of the POCs and ELOCs of CNGS and CTGS crystals on the light wavelength is investigated in the 600-1500nm range.

Design, fabrication, and characterization of high-temperature piezoelectric vibration sensor based on the Ho: CNGS crystal

In this letter, a Ho3+: Ca3NbGa3Si2O14 (Ho: CNGS) piezoelectric crystal with high quality and large size (Φ 34 mm × 52 mm) was grown by the Czochralski method, and a compressive mode piezoelectric vibration sensor with longitudinal d11 mode was fabricated based on the good properties of Ho: CNGS. The resistivity at elevated temperatures of Ho: CNGS could be enhanced significantly by doping Ho3+, and the ρ11 was three orders of magnitude higher than La3Ga5SiO14 and one order of magnitude higher than Ca3NbGa3Si2O14. The low dielectric loss and stable electro-elastic properties at high temperatures were also presented, and the electro-elastic constants were effectively improved compared with the pure Ca3NbGa3Si2O14 crystal. The sensor exhibited a maximum sensitivity temperature deviation of less than 5.2% from room temperature to 600 °C under the excitation frequency of 80 ̶ 315 Hz.

A novel yellow laser candidate: Dy3+ doped Ca3NbGa3Si2O14 crystal

In this article, a series of polycrystalline compounds of DyxCa3-xNbGa3Si2O14 (x = 0.03–0.45) were synthesized to obtain the proper Dy3+ ions doping concentration for the crystal growth. After that, a 5.58 at.% Dy:Ca3NbGa3Si2O14 (Dy:CNGS) single crystal was successfully grown by Czochralski method. Its spectral properties and Judd-Ofelt theory analysis were performed. The crystal has a relatively strong and wide absorption peak at about 453 nm with the absorption cross-section of 1.3 × 10−21 cm2 and a full width at half maximum (FWHM) of 10.2 nm. The Judd-Ofelt parameters Ω2, Ω4 and Ω6 were calculated to be 4.51, 2.93 and 0.19 × 10−20 cm2, respectively. The emission cross-section at 572 nm is 1.8 × 10−21 cm2 with a FWHM of 16.3 nm. The fluorescence time of the 4F9/2→6H13/2 transition is 0.24 ms. The results mean that Dy:CNGS crystal is a potential solid-state yellow laser material suitable for the commercial InGaN laser diode pumping.

Cr-doped Ca3NbGa3Si2O14: A promising near-infrared tunable laser crystal

Broad tunable solid-state lasers in the near-infrared region are urgently demanded due to their critical applications in optical communications, eye-safe imaging, medicine and spectroscopy, and Cr4+-based lasers exhibit good application prospect in this area. Herein, we reported a new near-infrared tunable laser crystal of Cr-doped Ca3NbGa3Si2O14 (Cr:CNGS). By employing the Czochralski method, single crystal of Cr:CNGS with dimensions of Φ 20 × 30 mm3 was grown. Its crystal structure, spectral properties were investigated in detail., Cr:CNGS exhibits attractive properties, including broad emission band at 800–1400 nm, long fluorescence lifetime (18 μs at 298 K) and good adaptability to LD pumping source, all of these characteristics enable it to be a potential laser crystal for the near-infrared tunable lasers. Notably, we discovered that the multi-sites in CNGS crystal make Cr ions exist in different valence states simultaneously, including Cr3+, Cr4+ and Cr5+, which is also partly responsible for its broadband emission.

Stable dielectric, elastic, and piezoelectric properties of Yb3+:CNGS crystals at high temperature

In this study, Yb3+:Ca3NbGa3Si2O14 (Yb3+:CNGS) single crystals with different doping concentrations (2 and 5 at%) were grown using the Czochralski method. The dielectric, elastic, and piezoelectric coefficients at room temperature and elevated temperature were measured and calculated according to the impedance method for the first time. Crystals show excellent piezoelectricity and exhibit favorable temperature stability from room temperature to 800 °C. The transmittance spectrum of the Yb3+:CNGS crystals is also recorded, and the results prove the high optical quality of these crystals.

759 fs pulse generation with Nd3+-doped CNGS ordered crystal based on a semiconductor saturable absorber mirror.

A diode-pumped passively continuous wave mode-locked laser at 1064.2 nm based on an ordered Nd:CNGS crystal has been experimentally investigated (for the first time, to our knowledge). Stable mode-locked pulses with a duration of 759 fs were produced at a repetition rate of 43.2 MHz. It is the shortest pulse generation of mode-locked lasers based on Nd3+-doped ordered crystal, as far as we know. A maximum average mode-locked output power of 133 mW was obtained at the absorbed pumped power of 6.7 W, and corresponding single-pulse energy and peak power were determined to be 3.1 nJ and 4.1 kW, respectively. The results indicate that the Nd:CNGS as an ordered crystal is indeed a potential candidate as a femtosecond laser gain medium.

Growth and enhanced electro-elastic properties of Nd3+: CNGS crystals with ordered langasite structure

In this letter, the Nd3+: Ca3NbGa3Si2O14 single crystals with high doping concentration (2at%) were grown using the Czochralski pulling method. For the first time, the dielectric, elastic and piezoelectric properties of Nd3+: CNGS crystals were evaluated at room temperature. The electro-elastic coefficients obtained for CNGS at room temperature crystals were given. It is proved that Nd3+: CNGS crystals have larger dielectric constants, piezoelectric constants and elastic compliance, as compared with those of CNGS crystals. Also, the new data were presented on the temperature dependence of electro-elastic properties from 25°C to 900°C. It is shown that Nd3+: CNGS crystals have a favorable temperature stability and high mechanical quality factor Q within the temperature range of 25–600°C.

Growth and optical properties of a new CGG-type laser crystal Nd^3+:CNGS

A novel CGG-type laser crystal of Nd3+:CNGS is characterized, including crystal growth, structure, refractive index, spectroscopic and laser performance. For Nd3+:CNGS crystal, the unit-cell parameters are a = 0.88897 ( ± 8.89 × 10−5) nm, c = 0.497998 ( ± 4.85 × 10−5) nm and V = 0.28219 nm3. The refractive index no and ne of Nd3+:CNGS were calculated to be 1.772 and 1.854 respectively at 1065 nm. The transmittance spectra of Nd3+:CNGS were measured, four main absorption peaks were located at 586 nm, 748 nm, 804 nm and 804 nm respectively. The absorption cross-section in z-axis is 6.08 × 10−20 cm2 around 804nm. The strongest emission peak of the fluorescence spectra was located at 1064 nm with the emission cross-section of 6.81 × 10−20 cm2 for E//x polarization and the fluorescence lifetime was 255.6 μs. Moreover, the continuous-wave laser at 1065 nm was obtained with the maximum output power of 1.43 W in the z-cut sample for the first time to the best of our knowledge, the optical conversion efficiency was 29.3% and the slope efficiency was 31.0%, which indicated that Nd3+:CNGS crystal should be a promising gain material.

Annealing Effects for Ca3NbGa3Si2O14 Piezoelectric Single Crystals Grown by Micro-Pulling-Down Method

The langasite-type Ca3NbGa3Si2O14 [CNGS] piezoelectric crystals grown in Air and Ar were annealed under various temperatures and atmospheres and the effects of annealing on various properties were investigated. The absorption peaks around 360 and 500 nm of CNGS crystals grown in Air decreased by the annealing at 1300°C in Ar. On the other hand, the annealing at 1300°C in Air decreased transmittance in the range from 300 to 500 nm for the CNGS crystal grown in Ar. The results suggest that the absorptions around 350 and 500 nm originate from the excess oxygen and the post-annealing can control the oxygen content in the crystals.

Shaped crystal growth of langasite-type piezoelectric single crystals and their physical properties

We have grown shape-controlled langasite-type crystals by the micro-pulling-down (μ-PD) method. Columnar shaped La(3)Ta(0.5)Ga(5.5)O(14) (LTG), Ca(3)NbGa(3)Si(2)O(14) (CNGS), Ca(3)TaGa(3)Si(2)O(14) (CTGS), Sr(3)NbGa(3)Si(2)O(14) (SNGS), and Sr(3)Ta- Ga(3)Si(2)O(14) (STGS) crystals were grown using a Pt-Rh crucible with a 3-mm-diameter columnar die at the bottom. All grown crystals showed high transparency except for the peripheral area and diameter of approximately 3 mm. The chemical phases at the central parts of the grown crystals were identified as a single phase of langasite-type structure and their lattice parameters were almost the same as those of crystals grown by the Czochralski (Cz) method; however, some impurity phases were observed in the peripheral area. In X-ray rocking curve measurements, the grown crystals indicated equivalent crystallinity to the crystal grown by the Cz method. The piezoelectric constant d(11) of the CNGS crystal was 3.98 pC/N; this value is well correlated with those of previous reports.

SAW excitation properties on YX-cut of CNGS and SNGS single crystals

The paper presents numerical results on conductances of surface acoustic wave interdigital transducers (IDTs) on YX-cut Ca(3)NbGa(3)Si(2)O(14) (CNGS) and Sr(3)NbGa(3)Si(2)O(14) (SNGS) single crystals. It is shown that there is a strong bulk acoustic wave radiation from IDTs on YX-cut of CNGS single crystal in contrast to that of SNGS single crystal.

Crystal growth and dielectric, piezoelectric and elastic properties of Ca 3NbGa 3Si 2O 14 single crystal

Single crystals of Ca 3NbGa 3Si 2O 14 (CNGS) were successfully grown from stoichiometric melts by conventional Czochralski technique along the a-axis and two large (0 0 0 1) facets and two small (0 1 1¯ 0) facets appear in every crystal. High-resolution X-ray diffraction (HRXRD) results indicate that CNGS crystals have good quality and are free of low-angle boundaries. The relative dielectric constants, the piezoelectric strain constants and elastic compliance constants of CNGS single crystal, have been determined by an electrical bridge and resonant–antiresonant method. The two piezoelectric strain constants, d 11 and d 14, are 4.40×10 −12 coulomb per newton (C/N) and −10.44×10 −12 C/N, respectively. The elastic compliance constants were measured and elastic stiffness constants were calculated from piezoelectric equations.

Crystal growth and properties of Co 2+-doped Ca 3NbGa 3Si 2O 14 single crystal

In this paper, single crystal of cobalt (Co)-doped Ca 3NbGa 3Si 2O 14 (CNGS) has been grown along b-axis using the Czochralski technique. The structure of the crystal has been studied by the X-ray powder diffraction (XRPD) method. The differential scanning calorimetric experiment shows that the Co 2+-doped CNGS crystal melted at 1339.3 °C. The transmittance and fluorescence spectra of Co 2+-doped CNGS crystal were measured at room temperature.

Growth and dielectric properties of Ca 3NbGa 3Si 2O 14 crystals

A new langasite type single crystal Ca 3NbGa 3Si 2O 14 (CNGS) was grown by Czochralski (CZ) method. The structure of CNGS crystal was determined by X-ray powder diffraction, the lattice parameters were a=0.8087 ± 0.0001 nm, c=0.4974 ± 0.0002 nm, V=0.2817 ± 0.0002 nm 3; The congruency of CNGS was examined by measuring the chemical composition of the grown crystal by quantitative X-ray fluorescent (XRF) analysis. The melting point of CNGS crystal was measured by using the differential scanning calorimetry (DSC). Dielectric properties of (1 1 0) wafer plate were studied in the temperature range from 298.15 to 873.15 K; the frequency dependence of dielectric loss in the frequency range 10 Hz–13 MHz was measured.