Xiangxin Tian

Determination and analysis of the linear and second order nonlinear optical properties of Na 2 TeW 2 O 9

The linear and nonlinear optical properties of a new quaternary tungstate tellurite crystal Na2TeW2O9 (NTW) are reported. It transmits well from 0.45 to 5 μm. The refractive indices have been measured and the crystal exhibits flexible phase-matching properties. The complete set of second-order nonlinear optical coefficients were obtained using Maker Fringe techniques, with the largest d13 = 9.3 pm/V. The crystal supports noncritical phase-matching (θ = 90°, φ = ± 48.6°), at the incident wavelength of 1064 nm, the effective nonlinear coefficient (deff) is 6.9 pm/V. The crystal structure and calculations of the dipole moment are discussed to explain the second-harmonic generation of NTW compared with Cs2TeMo3O12. Considering its good linear and nonlinear optical properties, NTW is a good candidate for nonlinear optical applications, especially for 3-5 μm region.

Top-seeded solution growth and characterization of a Bi2Mo2.66W0.34O12 single crystal

Single crystals of Bi2Mo2.66W0.34O12 with dimensions up to 70 mm × 55 mm × 45 mm were successfully grown using a top-seeded solution growth (TSSG) method with a MoO3–WO3 mixture as a flux. The material crystallizes in centrosymmetric space group P21/c (no. 14), with unit cell parameters of a = 7.7212(8) A, b = 11.4938(12) A, c = 11.9970(12) A, and β = 115.5070(10)°. The as-grown crystals exhibit {100}, {010}, {011}, {110}, {021}, {012}, {120}, {−111}, {−102}, and {1−1−2} facets, which are in good agreement with the predicted growth morphology based on the Bravais–Friedel and Donnay–Harker (BFDH) method. High-resolution X-ray diffraction (HRXRD) measurement on the (040)-faced plate shows that the full-width at half-maximum (FWHM) of the rocking curve is 54′′, which indicates high crystal quality. Our measurements show that it melts congruently and exhibits a wide transmission range from 475 nm to 5200 nm. It is worth noting that Bi2Mo2.66W0.34O12 has a large birefringence (Δn = 0.24 at 480 nm), indicating that the crystal can be a promising polarizing optical material.

Optimized growth and electro-elastic properties of centimeter-sized piezoelectric crystals of Na2TeW2O9

Large sized crystals of Na2TeW2O9 with dimensions up to 75 × 35 × 25 mm3 were successfully grown using an optimized top-seeded solution growth method. The as-grown Na2TeW2O9 single crystal exhibits well-developed faces with the major forms {200}, {002}, {202}, and {220}, which are in superior accordance with the ideal morphology predicted by the Bravais–Friedel and Donnay–Harker methods. A complete set of room temperature elastic, dielectric, and piezoelectric constants of Na2TeW2O9 single crystals was determined using resonance techniques and impedance analysis. Our results show that Na2TeW2O9 exhibits excellent piezoelectric properties (d15 = −23.93 pC N−1, d24 = −20.34 pC N−1), making the crystal a promising candidate for piezoelectric applications. The relationship between the piezoelectric properties and the crystal structure is also discussed.

Rational Design of a LiNbO3-like Nonlinear Optical Crystal, Li2ZrTeO6, with High Laser-Damage Threshold and Wide Mid-IR Transparency Window

With existing and emerging technologies urgently demanding the expansion of the laser wavelengths, high-performance nonlinear optical (NLO) crystals are becoming indispensable. Here, a prospective NLO crystal, Li2ZrTeO6, is rationally designed by the element substitution of Nb for Zr and Te from LiNbO3, which has been recognized as one of the most commercial NLO crystals. Li2ZrTeO6 with R3 symmetry inherits the structural merits of LiNbO3 (space group R3 c) and thus meets the requirements for NLO applications, including noncentrosymmetric crystal structure, moderate birefringence, and phase-matchability. Moreover, it can be exploited to achieve more outstanding optical damage resistant behavior (>1.3 GW cm-2), exceeding 22 times that of LiNbO3, which is more suitable for high-energy laser applications. Notably, this compound displays the widest IR absorption edge (7.4 μm) among all of the noncentrosymmetric tellurates reported so far. These excellent attributes suggest that Li2ZrTeO6 is a promising candidate for providing high NLO performance. The substitution of Nb for Zr and Te from LiNbO3 demonstrates a viable strategy toward the rational design of NLO crystals with anticipated properties.

Tailored fabrication of a prospective acousto–optic crystal TiTe3O8 endowed with high performance

A prospective acousto–optic (A/O) crystal TiTe3O8 endowed with superior thermal features and appreciable transparency is rationally developed by a tailored approach, namely TeO2 (a material possessing outstanding A/O performance) in synergistic combination with TiO2. Using the selected Li2CO3–TeO2 fluxes, a high-quality and large-dimension single crystal of cubic TiTe3O8 is extracted through a high temperature top-seeded solution growth (TSSG) technique. Remarkably, TiTe3O8 contains a d0 transition metal cation, Ti4+, which is typically susceptible to second-order Jahn–Teller (SOJT) distortions, but surprisingly in a locally undistorted octahedral geometry. The high symmetry of TiTe3O8 makes it ideal for crystal processing and A/O device design. Notably, the tellurite crystal TiTe3O8 displaying an adequate A/O figure of merit is originally utilized to fabricate an A/O modulator that exhibits a high diffraction efficiency of 77%, which is competitive with the value reported for the TeO2 crystal. Such a tailored design enriches the family of A/O materials and opens up a viable route toward exploiting controlled fabrication of potential A/O materials.

Electric–elastic properties of a novel high-quality CdTeMoO6 piezoelectric crystal

Large sized crystals of CdTeMoO6 with dimensions up to 30 × 12 × 9 mm3 were successfully grown using the top-seeded solution growth technique with an optimized flux system. High resolution X-ray diffraction rocking curve measurements revealed that the full-width at half-maximum (FWHM) of the rocking curve was 36 arcsec from the (001) reflection, which indicated high crystal quality. A complete set of room temperature elastic, dielectric, and piezoelectric constants of CdTeMoO6 single crystals was obtained using both resonance techniques and impedance analysis. The results demonstrate that the CdTeMoO6 crystals exhibit intriguing piezoelectric and elastic properties. The piezoelectric coefficients d14 and d36 reached 20.14 pC N−1 and 7.58 pC N−1, respectively, and the corresponding electromechanical coupling coefficients k14 and k36 were up to 22.78% and 19.48%, respectively. Furthermore, the relationship between the crystal structure and piezoelectric properties is also investigated. Our observations indicate that CdTeMoO6 crystals are good potential candidates for piezoelectric applications.

Insights into the polymorphism of Bi2W2O9: single crystal growth and a complete survey of the variable-temperature thermal and dielectric properties

Bismuth layered Aurivillius oxides have attracted longstanding research interest due to their unique structural characteristics and outstanding performance in ferroelectric dielectrics. The complex phase evolution process as a function of temperature and pressure in this family also provides fascinating platforms for understanding the chemical origin of their versatility. Herein, high-quality single crystals of a bismuth layered Aurivillius oxide, Bi2W2O9, with dimensions up to 29 × 23 × 11 mm3 were successfully grown via the top-seeded solution growth (TSSG) method using a mixture of WO3 and Li2B4O7 as a flux. The material crystallizes in an unexpected centrosymmetric orthorhombic Pbcn (no. 60) space group with unit cell parameters a = 23.705(2), b = 5.4148(6), and c = 5.4345(6) A. A complete survey of the anisotropic and variable-temperature thermal and dielectric properties was carried out with the aim of gaining detailed insights into their polymorphism evolution process. The results demonstrate that, with increasing temperature, the compound undergoes complicated phase transitions and, by analogy, signatures of the transitions are summarized and compared with those in Bi2WO6 and Bi2MoO6. The phase sequences and transition mechanisms of Bi2W2O9 are proposed by careful inspection and estimation.

Characterization and optimization of the growth conditions of a novel Cs2TeW3O12 piezoelectric crystal

In this study, Cs2TeW3O12 (CTW) single crystals were grown successfully through a top-seeded solution growth (TSSG) method using TeO2 as a self-flux. We identified a complete set of growth process parameters suitable for facilitating the growth of a high-quality CTW crystal. The results indicate that, in the same thermal field and with an appropriate flux ratio, a smaller cooling rate of the melt facilitates the smooth growth of high-quality CTW single crystals. The melt-viscosity versus temperature curves for different flux ratios were measured, and their effects on the crystal quality were discussed. In addition, the morphology of the crystal can be controlled by adjusting the rotation speed and the orientation of the seed. To investigate piezoelectric performance, complete sets of dielectric, elastic, and piezoelectric coefficients of CTW crystals were measured using both resonance and impedance analysis. The piezoelectric coefficients d33 and d15 reached 19.1 pC N−1 and 25.9 pC N−1, respectively. The electromechanical coupling coefficient, k33, was 37.7%, slightly higher than that of Cs2TeMo3O12 (CTM). Furthermore, the extent of dipole moment and polyhedron distortion of the CTW crystal were analysed in detail, and the relationship between the crystal structure and the piezoelectric properties was also discussed.

Biaxial crystal β-BaTeMo_2O_9: theoretical analysis and the feasibility as high-efficiency acousto-optic Q-switch

The high efficiency acousto-optic modulators become indispensable in photonics and optoelectronics for the pulse generation and signal modulation in optical display and telecommunications. In this paper, the validity and feasibility of the biaxial crystals as acousto-optic mediums have been theoretically analyzed and confirmed by experiments using a biaxial crystal of β-BaTeMo2O9. The diffraction angle and diffraction efficiency of the β-BaTeMo2O9 acousto-optic Q-switch are determined to be 1.420° and 78.1%, which are comparable with that of TeO2 acousto-optic modulator at the identical operating wavelength of 1064 nm and 100 MHz, respectively. The minimum of the modulated pulse width can be achieved to be 6 ns at 5 kHz with Nd:YVO4 as the gain medium. The results not only provide an excellent acousto-optic medium, but also explore the field of biaxial acousto-optic medium for device fabrications.

Top-seeded solution growth and characterization of Raman crystal LiVMoO6

Single crystal LiVMoO6, with dimensions up to 20 mm × 15 mm × 12 mm, has been grown successfully for the first time from a high-temperature solution with MoO3 as a flux. LiVMoO6 crystalizes in the monoclinic system with space group C2/m (no. 12) and unit cell parameters of a = 9.3531(9) A, b = 3.6477(4) A, c = 6.647(4) A, β = 111.643° and Z = 2. The crystal structure consists of MO6 (M = Mo and V) and LiO6 octahedrons mutually combined via corner sharing to form a 3D network. The as-grown LiVMoO6 crystal has well-developed faces with major forms {1−11}, {−1−11}, {001}, {100}, {11−1}, and {−11−1}. The crystal exhibits good transmittance from 490 to 4950 nm. High-resolution X-ray diffraction (HRXRD) shows that the full-width at half-maximum (fwhm) of the rocking curve is 47.22′′, indicating high crystal quality. The refractive index coordinate is established using a polarizing microscope. Spontaneous Raman spectra along the Z-axis with different configurations exhibit strong Raman shifts at 963.7 cm−1 and 830.5 cm−1, which are comparable to those of crystalline YVO4. The results indicate that LiVMoO6 should be an excellent Raman crystal.