This paper presents a tunable dual-wavelength laser by integration of a semiconductor gain chip with silicon-micromachined grating and mirrors onto a silicon substrate. The wavelength tuning is demonstrated by rotating the micromirror. With one wavelength being tuned and the other fixed, the laser output presents a tunable spectral separation from -28.38 to +24.18 nm. The laser output reaches 2.9 mW with far-field divergences of 37° and 30° in the vertical and horizontal directions, respectively. Besides, line broadening is observed with the reduction of the spectral separation.

H. Cai;A. Q. Liu;X. M. Zhang;J. Tamil;定元 汤;剑 伍;Q. X. Zhang

Applied Physics Letters

2008

We report on a high-power diode-end-pumped polycrystalline Yb:Y ₂O₃ ceramic laser. Under the pump power of 27 W, Continuous-wave output power of 9.2 W at 1078 nm has been obtained. The laser had a threshold of 3.1 W and a slope efficiency of 41%. Comparative studies between the Yb:Y₂O₃ ceramic and the Yb:YAG single crystal lasers show that at the same doping concentration of the Yb-ions, higher laser efficiency can be obtained in the Yb:Y₂O₃ ceramic laser than in the Yb:YAG single crystal laser.

J. Kong;定元 汤;B. Zhao;J. Lu;K. Ueda;H. Yagi;T. Yanagitani

2005

We demonstrated passive mode-locking of a Nd:YAG ceramic laser by optical interference modulation in a GaAs wafer. The combined effect of Kerr nonlinearity and optical interference in GaAs acted as an artificial saturable absorber and resulted in mode-locking. Maximum average output power of the mode-locked laser was as high as 2.84W, with a slope efficiency of 48%. The mode-locked pulse duration was as short as 4.1 ps. To our knowledge, this is the shortest pulse obtained from all Nd:YAG lasers without dispersion compensation.

Guoqiang Xie;定元 汤;Jian Kong;列加 钱

Optics Express

2007-4-30

The change of third order nonlinearity in silica fibre caused by poling is stable under UV or thermal erasure. The third order nonlinearity, like the linear refractive index, can be modulated by UV irradiation alone.

W. Xu;P. Blazkiewicz;S. Fleming;定元 汤

2001

We report on the generation of 281.2 nJ mode locked pulses directly from an erbium-doped fiber laser mode-locked with the nonlinear polarization rotation technique. We show that apart from the conventional dissipative soliton operation, an all-normal-dispersion fiber laser can also emit square-profile dissipative solitons whose energy could increase to a very large value without pulse breaking.

X. Wu;定元 汤;H. Zhang;L. M. Zhao

Optics Express

2009-3-30

We report on our recent progress of fabricating Yb ³⁺ -doped Lu ₂ O ₃ transparent ceramics for 1 μm solid-state laser application. Well-dispersed 3.3 at.% Yb:Lu ₂ O ₃ nanopowders were synthesized using a co-precipitation method. Without using any sintering aids, the Yb:Lu ₂ O ₃ nanopowders could be densified by vacuum sintering at 1500°C/10 hours followed by HIPing at 1480°C/4 hours. Such obtained Yb:Lu ₂ O ₃ ceramics had not only dense microstructure and submicron grain size of about 0.6 μm, but also in-line transmission of 80.0% at 600 nm. Preliminary continuous wave (CW) laser experiments with an uncoated Yb:Lu ₂ O ₃ ceramic slab have demonstrated highly efficient CW laser oscillation at 1079.8 nm.

Danlei Yin;Jie Ma;Peng Liu;Bingqing Yao;Jun Wang;Zhili Dong;Ling Bing Kong;定元 汤

Journal of the American Ceramic Society

2019-5

We report on a diode-pumped passively mode-locked Nd:Gd _0.64Y _0.36VO ₄ laser with a Cr ⁴⁺:YAG saturable absorber. Q-switched mode locking (QML) with 90% modulation depth was obtained. The peak power of the mode-locked pulse near the maximum of the Q-switched envelope was estimated to be about 1.7 MW at the pump power of 12 W. Besides QML, continuous-wave mode locking was also experimentally realized, for the first time to our knowledge, in the laser under a strong intracavity pulse energy fluence. The mode-locked pulse width is about 2.96 ps at a repetition rate of 161.3 MHz.

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

Applied Physics B: Lasers and Optics

2005-8

Physics phenomena of multi-soliton complexes have enriched the life of dissipative solitons in fiber lasers. By developing a birefringence-enhanced fiber laser, we report the first experimental observation of group-velocity-locked vector soliton (GVLVS) molecules. The birefringence-enhanced fiber laser facilitates the generation of GVLVSs, where the two orthogonally polarized components are coupled together to form a multi-soliton complex. Moreover, the interaction of repulsive and attractive forces between multiple pulses binds the particle-like GVLVSs together in time domain to further form compound multi-soliton complexes, namely GVLVS molecules. By adopting the polarization-resolved measurement, we show that the two orthogonally polarized components of the GVLVS molecules are both soliton molecules supported by the strongly modulated spectral fringes and the double-humped intensity profiles. Additionally, GVLVS molecules with various soliton separations are also observed by adjusting the pump power and the polarization controller.

Yiyang Luo;Jianwei Cheng;Bowen Liu;Qizhen Sun;Lei Li;Songnian Fu;定元 汤;Luming Zhao;德明 刘

Scientific Reports

2017-12-1

The spectral properties of a diode-pumped Yb:Y₂O₃ ceramic laser are reported. We show experimentally that the instantaneous emission wavelengths of the laser change randomly with time, whereas its emission has fixed well-defined transverse modes. The central wavelength of the laser emission also shifts prominently with the increase of intracavity light intensity. It is found that the spectral properties of the laser can be explained well based on the strong reabsorption of light in the gain medium.

J. Kong;定元 汤;J. Lu;K. Ueda

Optics Letters

2004-1-1

In fiber Bragg grating (FBG) sensors, detecting the Bragg wavelength accurately could be difficult due to a low signal-to-noise ratio (SNR) in the FBG spectrum. Two common sources of noise are the general random noise from the broadband sources and the interferometric noise caused by the residual reflections in the sensor system. Conventional filtering techniques could be quite effective in removing random Gaussian-white noise, but not so for the interferometric noise, which is very structured. On the other hand, parameter estimation techniques such as nonlinear least squares can be used to identify the parameters in the interferometric noise and remove it accordingly. However, since the parameter estimation problem is nonlinear, the larger the number of parameters, the higher the chance that the algorithm will get trapped into a local minimum and fail to identify the correct parameters. In this paper, it is proposed to combine the nonlinear least squares method with a Kalman smoother. Hence, the number of parameters to be estimated by the nonlinear least squares algorithm will be greatly reduced. To do this, a continuous-time linear time-varying state-space model is derived for the FBG spectrum and then the model is discretized so that the Kalman smoother can be applied. An interesting point to note is that this model is linear time-varying instead of nonlinear, thus not requiring an extended Kalman filter. Computer simulations are provided in the paper to demonstrate the effectiveness of the proposed method, followed by applications to real experimental data. Improvements in the accuracy of Bragg wavelength detection are observed.

定元 汤;Y. C. Chu;C. C. Chan;S. Liu

2006