Excess additives in laser ceramics compromise the physical nature and degrade the laser performance, and should be diminished properly in order to improve the quality of the laser ceramics. In this work, highly transparent Yb:Y₂O₃ceramics were fabricated by using low-level ZrO₂-MgO as double-sintering aid and vacuum sintering. Morphology and particle size of the ball-milled ceramic powders were studied by using transmission electron microscopy (TEM) and Rietveld refinement. Phase composition, microstructure and optical transmittance of the sintered ceramic samples were investigated by using X-ray diffractometer (XRD), scanning electron microscopy (SEM) and UV-VIS-NIR spectrometer. The optimized additive concentrations were found as low as 0.8 wt% for ZrO₂and 0.075 wt% for MgO, and the corresponding Yb:Y₂O₃ceramic sample fabricated had the transparency as high as 79.4% at 1200 nm and 81.5% at 2000 nm. A possible sintering mechanism was proposed and discussed in this paper. It is expected that the elevated laser performance will be produced in this low-level additive induced Yb:Y₂O₃transparent ceramics.

Kaijie Ning;Jun Wang;Dewei Luo;Zhi Li Dong;Ling Bing Kong;定元 汤

Journal of Alloys and Compounds

2017

Period-doubling of vector solitons in a ring fiber laser was experimentally observed for the first time. Apart from period-doubling of single vector soliton, period-doubling of multiple vector solitons was observed as well. Numerical simulation verified the experimental observation.

L. M. Zhao;定元 汤;H. Zhang;X. Wu;C. Lu;H. Y. Tam

Optics Communications

2008-11-15

We report on a diode-end-pumped passively Q-switched Nd:YAG ceramic laser. By using a Cr^4+::YAG single crystal of 80% initial transmission as the saturable absorber, stable Q-switched pulses with 126 μ J pulse energy, 12 ns pulse width and 8.4 kHz pulse repetition rate have been obtained.

J. Kong;定元 汤;G. Q. Xie

2007

We report experimental observation of passive harmonic mode locking of bunches of single-pulse solitons or twin-pulse solitons in an Erbium-doped fiber ring laser. It shows that harmonic mode locking is a general feature of the laser. The fundamental unit in a harmonically mode locked state could have various pulse compositions.

L. M. Zhao;定元 汤;T. H. Cheng;H. Y. Tam;C. Lu

2007

Sesquioxide single crystals, such as Y2O3, Lu2O3, and Sc2O3, have excellent thermal conductivity, thermal expansion coefficient, and relatively small phonon energy. They are the desired host materials for high power solid state lasers [1]. However, due to their high melting temperature it is extremely difficult to grow large size good optical quality sesquioxide single crystals, which prevented the wide applications of the materials as solid-state laser gain hosts. Different from the single crystal growth, ceramics are sintered at a temperature below the melting point, especially with the progress of nano-material synthesis technology high sinterability nanopowders could now be produced. Using nanopowders high quality ceramics can be sintered at even lower temperature. In this talk we show that by using the in-house synthesized nano-powders and the vacuum sintering plus hot isostatic pressing (HIP) method, high optical quality transparent sesquioxide ceramics can be produced even without using sintering aids. Rare-earth doped sesquioxide laser ceramics are fabricated and their high efficiency laser emission at 1.0µm, 2.0µm, and 3.0µm wavelength regions are experimentally demonstrated.

Jun Wang;Danlei Yin;Peng Liu;Jie Ma;Ying Wang;定元 汤

2019

Lithium insertion is the fundamental electrochemical process of rechargeable lithium batteries. We report here in situ Raman and atomistic simulation studies of the lithium insertion process in β-AgVO₃ nanowired structure material. Key issues of the process relate to structural variations and lithium migration pathways in the β-AgVO₃. The simulation model shows good agreement with the experimental results. It indicates that the lithium insertion can be divided into three steps. The reduction sites at each step in the β-AgVO₃ lattice are confirmed: the most favorable reduction sites at higher potential are V1/V4; at medium potential, Ag2/Ag3 are reduced and substituted; after that Li⁺ ion reduces V2/V3/Ag4 and further reduces V1/V4. The migration pathways of Li⁺ ions in β-AgVO₃ are proposed for the first time. Our discovery would help us to greatly understand the deep insight of the Li⁺ insertion process in lithium batteries.

Qiaoliang Bao;Shujuan Bao;Chang Ming Li;Xiang Qi;春旭 潘;剑锋 臧;Weiliang Wang;定元 汤

Chemistry of Materials

2007-11-27

We report on the experimental observation of period-doubling bifurcation and period-doubling route to chaos in a femtosecond soliton fiber laser passively mode locked by using the nonlinear polarization rotation technique. Increasing energy of the solitons circulating in the laser cavity, it was revealed that the intensity pattern of the output solitons experiences a period doubling route to chaos. Period-doubling route to chaos is a universal property of the nonlinear dynamic systems transiting from a stable state to a chaotic state. This experimental result shows that the nonlinear propagation of soliton pulses in the laser cavity is an intrinsic dynamic process, which follows the universal laws of the nonlinear dynamic systems.

L. M. Zhao;定元 汤;F. Lin;B. Zhao

Optics Express

2004-9

Neodymium-doped yttrium aluminum garnet (Nd:YAG) nanopowders were synthesized by the carbonate coprecipitation method. The effects of freeze drying and conventional oven drying of the precursor on the agglomeration of the Nd:YAG nanopowders were compared. The optical properties of the Nd:YAG nanopowders and the corresponding sintered Nd:YAG transparent ceramics were also investigated. The Nd:YAG nanopowders synthesized from freeze-dried precursor showed better dispersion and narrower particle size distribution compared with the powders synthesized from conventional oven drying. As a result, the Nd:YAG nanopowders synthesized from freeze-dried precursor have good sinterability, and Nd:YAG transparent ceramics were fabricated by vacuum sintering at 1750°C for 5 h.

Hua Gong;定元 汤;Hui Huang;Jan Ma

Journal of the American Ceramic Society

2009-4

Ultrashort soliton source, with very high repetition rate, is a necessity for next generation optical fiber communication. A very simple passively mode-locked fiber ring laser centered at 1566 nm, which is based on the modulation instability (MI) theory, is proposed. Using high Erbiumdoped (6470ppm) Bismuth fiber, a soliton pulse train, with 660 GHz repetition rate and pulse width of 420 fs, has been observed in a 11.5m short cavity for the first time.

Y. D. Gong;P. Shum;定元 汤;C. Lu;X. Guo

Optics Express

2003-10

The mode-locking of a ceramic Nd:yttrium aluminum garnet (YAG) solid-state laser (SSL) with solution processed graphene as saturable absorber (SA) was demonstrated. Transform-limited pulses with duration of 4 ps centered at 1064 nm were generated for a nondispersion compensated Nd:YAG SSL. Z -scan studies revealed that the graphene SA has a saturation intensity of 0.87 M W cm-2 and a normalized modulation depth of 17.4%. Our results illustrate the potential of using graphene as a mode locker for SSLs.

W. D. Tan;C. Y. Su;R. J. Knize;G. Q. Xie;L. J. Li;定元 汤

Applied Physics Letters

2010