Shijia Sun

Synthesis of SnO2 nanostructures by carbothermal reduction of SnO2 powder

The mass preparation of SnO2 nanobelts and nanowires has been achieved by carrying out the reaction of SnO2 powder and graphite at 1150°C. A metallic catalyst and vacuum conditions are not necessary. The temperature of the substrates and the concentration of oxide vapour were the critical experimental parameters for the formation of different morphologies of SnO2 nanostructures. The as-synthesized SnO2 nanobelts formed in region II are single crystalline with a [101] growth axis, with widths ranging from 50 to 500 nm, width-to-thickness ratios of 5–10, and lengths up to a few millimetres.

Growth and spectral characteristics of a new promising stoichiometric laser crystal: Ca9Yb(VO4)7

Abstract A Ca 9 Yb(VO 4 ) 7 crystal with dimensions of Φ23 mm×35 mm was grown successfully by Czochralski method. Its thermal conductivity was 1.06 W/(m·K) at room temperature. The absorption cross-sections at 980 nm were 1.80×10 −20 cm 2 and 1.28×10 −20 cm 2 for π-and σ-polarizations, respectively, with a full-width at half-maximum of 34 nm. The crystal had a broad emission at around 1025 nm with a full-width at half-maximum of 67 nm for π-polarization and 70 nm for σ-polarization. The emission cross-sections of the crystal were calculated by using reciprocity method and Fuchtbauer-Ladenburg formula. The emission cross-sections at 1025 nm were 3.57×10 −20 cm −2 and 1.91×10 −20 cm −2 for π- and σ-polarization, respectively. The fluorescence lifetime was 332 μs. The results indicated that the crystal is a promising femtosecond and tunable laser material.

Growth, structure, spectral and laser properties of Yb3+:LaMgB5O10 – a new laser material

A bulk crystal of Yb3+:LaMgB5O10 was grown successfully by the top seeded solution growth method for the first time to our knowledge. The detailed crystal structure data was given, revealing that the Yb3+:LaMgB5O10 crystal belongs to the monoclinic system with the space group P21/n, and its unit cell parameters are: a = 8.8002 A, b = 7.6136 A, c = 9.4900 A, β = 92.46°, V = 635.3 A3 and Z = 4. Investigation of its polarized spectral properties shows that the Yb3+:LaMgB5O10 crystal has broad, strong absorption and emission cross-sections. A continuous wave laser output of 2.76 W with a slope efficiency of 64.5% was obtained; the laser simultaneously oscillated at 1053 and 1057 nm at a pump power of 7.7 W. The results show that the Yb3+:LaMgB5O10 crystal is a promising laser crystal.

A promising ultrafast pulse laser crystal with a disordered structure: Yb3+:Sr3Gd2(BO3)4

A Yb3+-doped Sr3Gd2(BO3)4 (Yb:SGB) crystal was grown using the Czochralski method. A systematic investigation of the disordered structure characteristics, polarized spectral properties and continuous wave (CW) laser performances of this crystal was reported for the first time. Due to the statistical distributions of Gd3+ and Sr2+ ions, the absorption and emission spectra are strongly inhomogeneously broadened when introducing Yb3+ in the host. This feature of the broad spectra facilitates efficient pumping of InGaAs diodes and production of ultrafast pulse lasers. A maximum CW laser output power of 2.82 W under an absorbed pump power of 6.4 W was achieved with a central wavelength of 1055 nm, corresponding to a slope efficiency of 54% and an optical conversion efficiency of 44%. The results reveal that Yb:SGB is an excellent candidate for an ultrafast pulse laser crystal.

Thermal, Spectral and Laser Properties of Er3+:Yb3+:GdMgB5O10: A New Crystal for 1.5 μm Lasers

A novel laser crystal of Er3+:Yb3+:GdMgB5O10 with dimension of 26 × 16 × 12 mm3 was grown successfully from K2Mo3O10 flux by the top seeded solution growth method. The thermal diffusivity and specific heat capacity were measured to calculate the thermal conductivity of the crystal. The absorption and fluorescence properties of the crystal at room temperature were investigated in detail. The Judd-Ofelt method was used to analyze the polarized absorption spectra. The emission cross-section of the 4I13/2→4I15/2 transition was calculated by the Füchtbauer-Ladenburg formula and the relevant gain cross-sections were estimated. Continuous-wave laser output of 140 mW at 1569 nm with the slope efficiency of 17.8% was demonstrated in a plano-concave resonator. The results reveal that Er3+:Yb3+:GdMgB5O10 crystal is a promising material for 1.5 μm lasers.

A new ~1 μm laser crystal Nd:Gd 2 SrAl 2 O 7 : growth, thermal, spectral and lasing properties

Nd:Gd2SrAl2O7 crystals were grown by the Czochralski technique; thermal, spectral and laser properties were investigated in detail. The average thermal expansion coefficients along a- and c-axis are 12.6 × 10−6 K−1 and 14.9 × 10−6 K−1, respectively. At room temperature, the thermal conductivities are 4.98 and 5.24 W (m−1 * K−1) along the a- and c-axis, respectively. The absorption cross sections at ~808 nm are 13.7 × 10−20 cm2 with a FWHM of 3.3 nm for π-polarization and 11.84 × 10−20 cm2 with a FWHM of 3.4 nm for σ-polarization. The emission cross sections at ~1080 nm are 15 × 10−20 cm2 and 12.7 × 10−20 cm2 with a FWHM of about 5.1 nm and 12.5 nm for π- and σ-polarization, respectively. The fluorescence lifetime for the 4F3/2 → 4I11/2 transition was fitted to be 118 µs. Pumped by a fiber-coupled 808 nm laser diode, the maximum 1.55 W continuous-wave laser output at ~1.08 µm was achieved with a slope efficiency of 30.5%. All the results show that Nd:Gd2SrAl2O7 crystal is a promising laser material.

Exploring the mode-locking laser performance of Yb:LaMgB 5 O 10 crystal

The spectral properties of 5 at.% doped Yb:LaMgB5O10 (Yb:LMB) crystal were presented and discussed in detail. The large absorption and emission cross sections, broad emission spectral lines, and considerably good thermal conductivity indicate the considerable potential of Yb:LMB for efficient and powerful ultrashort laser application. In the experiment, the semiconductor saturable absorber mirror (SESAM) mode-locked Yb:LMB laser generated pulses with the pulse duration of 182 fs and the central wavelength of 1025.2 nm. The maximum average power was 2.49 W with the slope efficiency of 48% and the optical to optical efficiency as high as 32%. Furthermore, pulses of 148 fs with average output power of 1.52 W and 108 fs with 0.61 W were obtained based on Yb:LMB crystal. To the best of our knowledge, this is the first demonstration of mode-locked pulse generation from the Yb:LMB laser.