Due to its potential as a compact, stable light source of ultrashort pulses, passively mode locked fibre soliton lasers have been intensively investigated recently. An important issue of the studies has been how to efficiently utilize the gain bandwidth to produce shortest pulses. There are two mechanisms that prevent the pulse shortening in the laser. One is the pulse splitting, which is due to the fact that the total loss from the saturable absorber and the cut-off of the gain bandwidth is smaller for two broader pulses than for one sharp pulse, provided that they have the same total energy. The other one is the resonant sideband formation in the laser. When there is discrete perturbation in the cavity, a soliton circulating in the cavity will reshape its form and shed the excess energy into dispersive waves. A resonant energy transfer occurs between the soliton and those dispersive waves whose phase is matched to the soliton. The energy transfer rate depends on the overlapping between the resonant sidebands and the soliton spectrum. With the same sidebands a shorter soliton pulse will have higher energy transfer rate and will therefore stop shortening when all energy injected into the soliton pulse is transferred to the dispersive waves. In this paper we study further the dynamics of a passively mode locked fibre soliton laser as the laser gain is increased. We show experimentally that under a resonant soliton energy transfer to the dispersive waves, new soliton pulses can be formed through soliton shaping of dispersive waves in the laser.

W. S. Man;H. Y. Tam;定元 汤;P. D. Drummond

1999

The collective dynamics of an optically pumped bidirectional ring laser is studied experimentally. Under the nonlinear interaction between the forward and backward modes of the laser, the laser can show strong antiphase dynamics. Under the chaotic laser mode-mode interaction, the laser can show spontaneous self-organization as well. Spontaneous chaotic synchronization of the laser mode dynamics is observed in the laser under a particular experimental condition.

定元 汤;N. R. Heckenberg;C. O. Weiss

1996

Control of chaos in the single-mode optically pumped far-infrared [formula presented] laser is experimentally demonstrated using continuous time-delay control. Both the Lorenz spiral chaos and the detuned period-doubling chaos exhibited by the laser have been controlled. While the laser is in the Lorenz spiral chaos regime the chaos has been controlled both such that the laser output is cw, with corrections of only a fraction of a percent necessary to keep it there, and to period one. The laser has also been controlled while in the period-doubling chaos regime, to both the period-one and -two states.

R. Dykstra;定元 汤;N. R. Heckenberg

Physical Review E

1998

We report on the passively Q-switched mode-locking of a quasi-cw (QCW) diode pumped Nd:GdVO₄ laser with Cr⁴⁺:YAG saturable absorber. We show that by using the QCW pumping high quality Q-switched mode-locking can be easily obtained in the laser even with a simple two-mirror laser cavity configuration. Mode locked pulses with pulse width of about 1 ps at repetition rate variable from 500 MHz to 1 GHz has been obtained.

S. P. Ng;定元 汤;J. Kong;Z. J. Xiong;T. Chen;L. J. Qin;X. L. Meng

Optics Communications

2005-6-1

High efficiency continuous-wave laser operation of an in-house made Nd:Y₂O₃ ceramic was demonstrated. The Nd:Y₂O₃ laser ceramic was fabricated by vacuum sintering plus the hot isostatic pressing process, whose in-line transmittance reaches 81.6% at the wavelength of 1000 nm. The 1.08 and 1.36 μm CW laser oscillation of an uncoated ceramic sample was experimentally investigated. Both achieved the highest slope efficiency and output power so far reported for the Nd:Y₂O₃ ceramic lasers. For the operation of ⁴F3/2-⁴I11/2 transitions, simultaneous oscillations at 1074.6 nm and 1078.8 nm were observed. At an absorbed pump power of 7.0 W, a maximum output power of 3.01 W was obtained with a slope efficiency of 49.6%. For the laser operation of 4F_3/2-4I_13/2 transitions, a 1.68 W single wavelength at 1357.7 nm with the slope efficiency of 29.3% was achieved at the absorbed pump power of 6.7 W.

Haiyong Zhu;Yongchang Zhang;Danlei Yin;Jun Wang;Yanmin Duan;Jing Zhang;Peng Liu;定元 汤

Optical Materials Express

2018

High-order Stokes around 1.2 μm generated by Nd:YAG∖KTiOAsO₄ (KTA) cascaded Raman laser is presented. The fundamental and low-order (first to third) Stokes lines were well restricted in the cavity. The KTA Raman laser output starts with single Stokes emission at 1182 nm. As the incident pump power was increased, Stokes emission at 1178, 1216 and 1212 nm appeared in sequence. The total output power of 1.03 W and the conversion efficiency of 10.1% were obtained at the incident pump power of 10.2 W and the pulse repetition frequency of 15 kHz. The results show the cascaded Raman of KTA can enrich laser spectral lines and generate high-order Stokes light.

Junhong Guo;Yanmin Duan;Hongyan Wang;Haiyong Zhu;Pengfei Wei;Jian Zhang;Luming Zhao;定元 汤

Optical Materials

2017-9

Nanosized neodymium doped yttrium aluminum garnet (Nd:YAG) powders have been synthesized by a modified sol-gel combustion method by using nitrate salts as starting materials. Phase evolution, morphology, and microstructure of the synthesized powders were investigated. Solvent plays an important role in the phase formation of the precursor. Crystallized Nd:YAG powders can be directly obtained at as low as 800 °C without the formation of any intermediate phase. The crystallization kinetics of amorphous YAG precursor was studied by variable heating rate of DTA. The activation energy for crystallization of the YAG by modified sol-gel combustion is 361.7 kJmol^-1, which is much lower than 480.6 kJmol^-1 determined from that by general sol-gel combustion. The as-prepared powders are well crystallized and soft aggregated with average crystalline size about 60 nm at 1200 °C. Good luminescent property is observed in the Nd:YAG nanopowders and the emission intensity increased with increasing the calcination temperatures.

Hua Gong;定元 汤;Hui Huang;Man Di Han;Ting Sun;Jian Zhang;Xian Peng Qin;Jan Ma

Journal of Crystal Growth

2013-1-1

A new approach to outputting 2 μm light was proposed based on non-critical phase matching KTA-OPO intra-cavity pumped by Nd: YVO₄ crystal laser. A signal light with a power exceeding 1 W at 2093 nm is obtained with a diode-to-signal efficiency up to 10%. The short pulse width is about 3.4 ns at 30 kHz and the spectrum width at 2 μm waveband is only about 1 nm. The results show that this approach is also an efficient way to achieve 2 μm pulsed laser with high peak power.

Zhengrong Feng;Haiyong Zhu;Yanmin Duan;定元 汤;Hongyan Wang

Qiangjiguang Yu Lizishu/High Power Laser and Particle Beams

2013-4

A passively mode locked soliton fiber ring laser was successfully demonstrated and transform limited soliton pulse with FWHM width of 158 femto second was achieved. A 1480/1550 wavelength-division-multiplexing (WDM) coupler which was made of dispersion shifted fiber (DSF) was used to couple the pump light into the ring cavity. It was found that shorter pulses can be generated by reducing the cavity length and the net GVD inside the laser cavity.

P. Shum;Y. D. Gong;定元 汤

Proceedings of SPIE - The International Society for Optical Engineering

2002

Dy³⁺-doped Y₂O₃ ceramics were fabricated by Spark Plasma Sintering method. The effect of sintering temperature on the microstructure and the optical transmittance of the ceramics was studied. The maximum in-line transmittance of Dy:Y₂O₃ ceramics with thickness of 1 mm was 74.5% at 574 nm when sintering temperature was 1550 ℃. The spectroscopic parameters were determined by Judd-Ofelt theory based on the room temperature absorption spectra. The peak emission cross section for the ⁴F_9/2 → ⁶H_13/2 transition was calculated to be 0.569 × 10⁻²⁰ cm². The fluorescence decay curve and quantum efficiency of the ⁴F_9/2 multiplet were measured to be 269.2 μs and 37.1%, respectively.

Zongwen Hu;Xiaodong Xu;Jun Wang;Peng Liu;Dongzhen Li;Xiaodan Wang;Jian Zhang;军 徐;定元 汤

Journal of the European Ceramic Society

2018-4