Jian Zhang

Highly transparent Nd 3+ :Lu 2 O 3 produced by spark plasma sintering and its laser oscillation

Laser oscillation was demonstrated using a 1 at.% Nd3+-doped Lu2O3 (Nd3+:Lu2O3) transparent ceramic produced by spark plasma sintering. Nd2O3, Lu2O3, and LiF commercial powders were mixed by ball milling and were sintered at 1723 K using a two-step sintering profile. After the transparent Nd3+:Lu2O3 ceramic was annealed in air, its transmittance at 1076 nm reached 81.8%, which was close to the theoretical value for Lu2O3 (82.2%). The absorption cross-section at 806 nm was 1.29 × 10−20 cm2, and the fluorescence decay time at 1076 nm was 229 μs. The laser oscillation of Nd3+:Lu2O3 ceramic for the transition from 4F3/2 to 4I11/2—specifically, at 1076.7 and 1080.8 nm—was simultaneously obtained, with a laser output of 0.21 W and slope efficiency of 14%.

Continuous-wave laser operation of Nd:LuAG ceramic with 4 F 3∕2 → 4 I 11∕2 transition

The diode-end-pumped continuous-wave Nd:LuAG ceramic lasers at 1064 nm and 1123 nm with 4F3∕2→4I11∕2 transition are here presented for the first time. For the 1064 nm laser operation, the output has been optimized using output couplers with different transmissions. A maximum output power of 8.3 W was achieved under an incident pump power of 20.4 W with a conversion efficiency of 40.7%. Replacing the output coupler based on reasonable coating design for 1123 nm oscillation, a continuous-wave laser with single-wavelength at 1123 nm was obtained with the same ceramic. At an incident pumped power of 20.4 W, an output power of 3.5 W was achieved with a conversion efficiency of 17.2%.

Effect of γ-Al2O3 additives on the microstructure of Y2O3 ceramics

AbstractnThis paper reported the fabrication of Y2O3 transparent ceramics with γ-Al2O3 doped as the sintering aid under vacuum using the co-precipitated Y2O3 powders as raw materials. The different concentrations of γ-Al2O3 were employed for investigating the effect on the microstructures and densities of Y2O3 ceramics. The doped sintering aid could achieve fine microstructure and high density. The average grain sizes were around 25xa0μm, and the relative densities were all above 98.5xa0%. The best sample was achieved with 0.08xa0wt% γ-Al2O3 when sintered at 1850xa0°C for 8xa0h. And the grain size and relative density were 25xa0μm and 99.47xa0%, respectively.

Full investigation into continuous-wave Nd:LuAG lasers on 4 F 3/2 → 4 I 13/2 transition around 1.3 and 1.4 μm

We report a full investigation of continuous-wave diode-pumped Nd:LuAG single crystal lasers on 4F3/2→4I13/2 transition around 1.3 and 1.4 μm. In free-running mode, a maximum output power of 4.18 W is achieved for a simultaneous dual-wavelength laser operation at 1321 and 1338 nm, which represents the highest output power for Nd:LuAG laser material at a 1.3 μm emission band. Three single wavelength lasers at 1340, 1332 and 1322 nm, as well as a dual-wavelength laser at 1334 and 1338 nm, are also generated with maximum output powers of 2.39, 2.63, 2.24 and 1.23 W, respectively, with the aid of a glass etalon. Moreover, a single wavelength laser at 1353 nm is also obtained with a maximum output power of 1.53 W. Furthermore, in free-running mode, simultaneous tri-wavelength eye-safe lasers at 1419, 1432 and 1442 nm are attained with a maximum output power of 1.83 W, and a 1.08 W single wavelength laser at 1419 nm is also yielded. Most of the 1.3 μm lasers and all of the 1.4 μm lasers are demonstrated for the first time to our knowledge. Thus, this work indicates that Nd:LuAG crystal is a very promising laser gain medium for high-power continuous-wave infrared laser generation.

Optical properties of Ho:YAG and Ho:LuAG polycrystalline transparent ceramics

Lutetium Aluminum Garnet (LuAG) is a garnet isostructure similar to Yttrium Aluminum Garnet (YAG). High quality Ho3+ doped YAG and LuAG transparent polycrystalline ceramics were fabricated successfully by a reactive sintering method under vacuum. The microstructures, absorption spectrum, fluorescence spectrum and the laser performances of Ho:YAG and Ho:LuAG ceramics were systematically investigated. The in-line transmittances of Ho:YAG ceramic in the visible and infrared region are higher than 82% and 84%. The absorption coefficient of 1.0 at.% Ho:LuAG is 0.88 cm−1 at 1906 nm and its absorption cross section is 0.62 × 10−20 cm2.

Ceramic Powder Synthesis

A wide range of methods have been used to synthesize ceramic powders, with different compositions. Although most of these methods are applicable to transparent ceramic power synthesis, some of them have not been employed in the fabrication of transparent ceramics. Solid-state reaction is still the key method, while wet-chemical routes are increasingly used, whereas gas-phase reactions are only limited to nonoxide ceramics. For large-scale applications, cost-effectiveness, environmental friendliness, and less energy consumption are all very important considerations, when selecting synthetic methods.

Efficient laser operation based on transparent Nd:Lu 2 O 3 ceramic fabricated by Spark Plasma Sintering.

Efficient laser operation of Nd:Lu₂O₃ ceramic fabricated by Spark Plasma Sintering (SPS) was demonstrated. Transparent Nd:Lu₂O₃ ceramic was successfully fabricated by Spark Plasma Sintering and its laser experiment was done. On the ⁴F_3/2 to ⁴I_11/2 transition, the obtained maximum output is 1.25W at the absorbed pump power of 4.15W with a slope efficiency of 38% and two spectral lines at 1076.7nm and 1080.8nm oscillated simultaneously. The slope efficiency of 38% is near two times higher than the previously demonstrated SPSed Nd:Lu₂O₃ ceramic lasers. On the ⁴F_3/2 to ⁴I_13/2 transition, the laser operated at the wavelength of 1359.7nm and the maximum output of 200mW was obtained at the absorbed pump power of 2.7W.

Nd:LYAG and Nd:LGAG Mixed Crystals: Potential Candidates for 1.83 μm Laser Source

We report here, for the first time, diode-pumped continuous-wave laser operation of Nd:LuYAG (LYAG) and Nd:LuGdAG (LGAG) mixed crystals around 1.83 μm. Cooling the laser samples down to about 6 °C, output powers of about 0.56 and 0.46 W with slope efficiencies of about 5.5% and 5.6% can be achieved, respectively, for the two crystals. These Nd3±-doped garnet mixed crystals, like single crystal Nd:YAG, are believed to be the potential for laser generation at the important 1.83-μm near-infrared wavelength domain.

High-power and high-efficiency diode-pumped Nd:LuYAG mixed crystal lasers operating at 939 and 946 nm

We report on high-performance infrared lasers at 0.94xa0μm based on quasi-three-level transition of F3/24→I9/24 in Nd:LuYAG mixed crystal, for the first time to our knowledge. The maximum output power was achieved to 5.64xa0W with slope efficiency of approximately 52.5% at 946xa0nm. The simultaneous dual-wavelength laser at 939 and 946xa0nm is also obtained with maximum output power of 3.61xa0W and slope efficiency of 34.8% by introducing a glass etalon into the cavity. Moreover, a 2.0-W single-wavelength laser at 939xa0nm can be further attained by suitably tilting the etalon. Using a Cr:YAG saturable absorber, Q-switched laser operation is realized with maximum average output power of 0.68xa0W and the narrowest pulse width of 8.4xa0ns, which results in the maximum single pulse energy of approximately 55.3xa0μJ and the maximum pulse peak power of approximately 6.15xa0kW. Finally, thermal focal length of the laser crystal is estimated by using a flat-flat laser cavity.

Low-Complexity TOAD-Based All-Optical Sampling Gate With Ultralow Switching Energy and High Linearity

We present experimentally a low-complexity ultralow switching energy and high-linearity all-optical sampling gate based on a terahertz optical asymmetric demultiplexer, constructed by placing a polarization-insensitive multiple-quantum-well semiconductor optical amplifier (PI-MQW-SOA) asymmetrically within a fiber loop mirror. Using a picosecond pulse train as the trigger clock, we analyze, in detail, the influence of the sampling pulse power and the offset of the PI-MQW-SOA from the loop midpoint on the shape, width, and amplitude of the sampling window, respectively. Furthermore, the switching energy and linearity of this sampling gate under different widths of sampling windows are specifically investigated. Results demonstrate that our sampling gate possesses a switching energy as low as 25 fJ and a high linearity above 0.99.