Tetravalent chromium-doped Y₃Al₅O₁₂ ceramics were fabricated by solid-state reactive sintering method using high-purity Y₂O₃, α- Al₂O₃, and Cr₂O₃ powders as the starting materials. CaO and MgO were co-doped as the sintering aids. The effects of TEOS and divalent dopants (CaO and MgO) on the optical qualities, the conversion efficiency of Cr⁴⁺ ions, and the microstructure evolutions of 0.1 at.% Cr⁴⁺: YAG ceramics were investigated. Fully dense, dark brown colored Cr⁴⁺: YAG ceramics with an average grain size of 3.1 μm were achieved. The in-line transmittance of the as-prepared ceramic at 2000 nm was 85.3% (4 mm thick), and the absorption coefficient at 1030 nm (the characteristic absorption peak of Cr⁴⁺ ions) was as high as 3.7 cm^-1, which was higher than that of corresponding single crystals fabricated by Czochralski method.

Tianyuan Zhou;Le Zhang;Hao Yang;Xuebin Qiao;Peng Liu;定元 汤;Jian Zhang

Journal of the American Ceramic Society

2015-8-1

A diode-pumped Yb:LuAG ceramics laser was investigated. CW laser performance was achieved. Passively femtosecond mode-locked laser operation was also successfully realized by using a SESAM mirror. The mode-locked pulse duration as short as 650 fs was obtained with a maximum output power of 200 mW.

Dewei Luo;Jian Zhang;Changwen Xu;Hui Lin;Hao Yang;Haiyong Zhu;Guodong Shao;定元 汤;Lingbing Kong

Physica Status Solidi (C) Current Topics in Solid State Physics

2013-6

Bound solitons with a soliton pulse width of 326 fs and a pulse separation of 938 fs are obtained in a passively mode locked fiber laser. Its creation and annihilation mechanism is experimentally investigated. Due to the existence of a strong cw laser in the cavity, the generation of bound solitons is found to be different from that of the nonbound normal solitons. We find that the number of stable bound soliton pairs in the cavity can be controlled only under lower pump power.

Y. D. Gong;定元 汤;P. Shum;C. Lu;T. H. Cheng;W. S. Man;H. Y. Tam

Optical Engineering

2002-11

We have both experimentally and numerically investigated the satellite pulse generation in diode-pumped passively Q-switched Nd:GdVO₄ lasers with Cr⁴⁺:YAG saturable absorber. We show experimentally that satellite pulse generation is a general effect of the lasers under strong pumping, and its formation is always associated with the appearance of strong Q-switched pulses. Satellite pulse generation of the lasers is further numerically simulated based on a coupled rate-equation model. Our numerical simulations show that the phenomenon is caused by the finite lifetime of the lower laser energy level of the lasers.

S. P. Ng;定元 汤;列加 钱;L. J. Qin

IEEE Journal of Quantum Electronics

2006-7

Based on the open-aperture Z-scan measurement, we firstly uncovered the saturable absorption property of the topological insulator (TI): Bi2Se3. A high absolute modulation depth up to 98% and a saturation intensity of 0.49 GWcm ^-2 were identified. By incorporating this novel saturable absorber material into an erbium-doped fiber laser, wavelength tunable soliton operation was experimentally demonstrated. Our result indicates that like the atomic layer graphene, the topological insulator Bi2Se3 could also operate as an effective saturable absorber for the passive mode locking of lasers at the telecommunication band.

Chujun Zhao;Yanhong Zou;Yu Chen;Zhiteng Wang;Shunbin Lu;Han Zhang;双春 文;定元 汤

Optics Express

2012-12-3

Novel Ga-Sb-S chalcogenide glasses doped with different amount of Dy³⁺ ions were prepared. Their thermal stability, optical properties, and mid-infrared (MIR) emission properties were investigated. The glasses show good thermal stability, excellent infrared transparency, very low phonon energy (∼306 cm^-1), and intense emissions centered at 2.95, 3.59, 4.17 and 4.40 μm. Three Judd-Ofelt intensity parameters (Ω₂ = 8.51 × 10^-20 cm², Ω₄ = 2.09 × 10^-20 cm², and Ω₆ = 1.60 × 10^-20 cm²) are obtained, and the related radiative transition properties are evaluated. The high quantum efficiencies and large stimulated emission cross sections of the MIR emissions (88.10% and 1.11 × 10^-20 cm² for 2.95 μm emission, 75.90% and 0.38 × 10^-20 cm² for 4.40 μm emission, respectively) in the Dy³⁺-doped Ga-Sb-S glasses make them promising gain materials for the MIR lasers.

Mingjie Zhang;Anping Yang;Yuefeng Peng;Bin Zhang;He Ren;Wei Guo;Yan Yang;Chengcheng Zhai;Yuwei Wang;Zhiyong Yang;定元 汤

Materials Research Bulletin

2015-10-1

This letter develops a method that is able to optimize the grating pivot position to obtain maximum continuous tuning range for a Littrow laser, and also verifies the method by implementation of a single-chip integrated laser using the microelectromechanical systems (MEMS) technology. The laser consists of a semiconductor gain chip, a microlens, and a MEMS blazed grating arranged in the Littrow configuration. The laser is integrated onto a single silicon chip while maintaining the ability of continuous tuning in a large range. It has a compact size of 2.0 mm × 1.5 mm × 0.6 mm, and has obtained a tuning range of 30.3 nm with a resolution of 0.03 nm/V ², a maximum power of 0.4 dBm and a side mode suppression ratio of 26 dB. Other merits include fast tuning speed, improved mechanical/wavelength stability, batch fabrication, and low cost.

A. Q. Liu;X. M. Zhang;定元 汤;C. Lu

Applied Physics Letters

2004-10-25

We have systematically investigated solitary wave emission of the fiber lasers that are of net negative cavity group velocity dispersion (GVD) and are passively mode-locked with the nonlinear polarization rotation (NPR) technique. It was found experimentally that solitary pulses formed in the fiber lasers have a number of new features as compared with those of the solitons formed in single mode fibers. Apart from the well-known effects widely reported, such as the soliton sideband generation, multiple soliton pulse formation and soliton energy quantization, we also report on the experimental observation of soliton train nonuniformity, multi-hump solitons, soliton sub-sideband generation, soliton period-doubling bifurcations and route to chaos, soliton collapse and noise-like pulse emission. A detailed analysis on the NPR mode-locking of the fiber lasers is presented. Moreover, a roundtrip model, which takes account both the nonlinear pulse propagation in the cavity fibers and the laser cavity effects, is introduced for the numerical simulations on the solitary wave emission of the fiber lasers. We show that almost all the experimentally observed laser soliton features could be numerically reproduced with the model. Especially, based on the numerical simulations the formation mechanism of the various new soliton features could be well explained. A novel feature of the fiber lasers is that their cavity can generate a special kind of soliton peak clamping effect. It is this cavity effect that causes the multiple soliton formation in the lasers. The same cavity effect is also responsible for the stable soliton operation of the lasers under strong pumping, and soliton pulse train non-uniformity. A laser soliton is intrinsically a dissipative soliton, whose internal energy balance plays a crucial role on the soliton stability. We further show that without cavity peak clamping solitons formed in the lasers would eventually collapse under effect of laser gain. In addition, a laser soliton also subjects to the cavity induced soliton modulation instability (MI), which causes not only spectral subsideband generation on the soliton spectrum, but also soliton dynamic instability, such as soliton quasi-periodicity and period-doubling route to chaos.

定元 汤;L. M. Zhao

2009-10-1

A high performance thermoplastic polymer, polyetherimide (PEI), which is thermally compatible with some chalcogenide glasses, is introduced as a cladding material to fabricate fiber image bundles. As₂S₃/PEI image bundles consisting of 900 fibers are fabricated through a stack and draw approach. The loss of the fibers, the dark fiber ratio, the resolution and crosstalk of the image bundles are characterized. The As₂S₃/PEI shows a good transmitting property in the 2 mm to 6 mm spectral region. The background loss is about 0.5 dB/m, and the peak loss at 4.0 μm due to S-H impurity absorption is about 3.5 dB/m. The fiber bundle containing 900 fibers with a diameter of 80 μm has a dark fiber ratio of 1%, exhibits a resolution of 7 line/mm and shows crosstalk of 1%. Clear infrared image of a soldering iron tip is obtained through this fiber bundle. The flexibility of the fiber bundles is achieved by dissolving the PEI into a solvent dimethylacetamide (DMAC). Flexible high-resolution chalcogenide fiber image bundles may be fabricated through the stack and draw approach using a thermoplastic polymer which can be dissolved into special solvents as an interlayer material similar to the 'acid-dissolved glass'.

Chengcheng Zhai;Bin Zhang;Sisheng Qi;Wei Guo;Zhiyong Yang;Anping Yang;Mingjie Zhang;Yan Yang;Yi Yu;Rongping Wang;Guangming Tao;定元 汤;Barry Luther-Davies

Guangxue Xuebao/Acta Optica Sinica

2015-8-10

We show experimentally that under suitable conditions two globally coupled laser modes showing chaotic dynamics can spontaneously synchronize together. Under the synchronization the frequencies of the two modes lock together and the chaotic dynamics of each mode show similarities to those of the single-mode laser.

定元 汤;R. Dykstra;N. R. Heckenberg

Physical Review A - Atomic, Molecular, and Optical Physics

1996