An actively harmonic mode locked fiber ring laser was setup, stability under the nearby of harmonic modulation frequency was analyzed. A new cavity length feedback system was implemented to realize the long-term stability. A chaos phenomena in the actively harmonic mode locked fiber ting laser was observed.

Y. D. Gong;P. Shum;Q. Wen;定元 汤

Proceedings of SPIE - The International Society for Optical Engineering

2002

We report on an efficient diode-end-pumped polycrystalline Yb:Y₂O₃ ceramic laser. Continuous-wave output power of 4.2 W at 1078 nm was obtained under pump power of 19.5 W. The corresponding slope efficiency was 29%. The beam quality factor (M²) at full pump power was measured to be 1.63. The threshold wavelengths of the laser at various output couplings were also investigated. It was found that the threshold wavelengths shifted ~5 nm when the ref lectivity of the output coupler changed from 90% to 99.9%, as caused by the strong reabsorption effect in the ceramic sample.

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

Optics Letters

2004-6-1

This letter presents the results of stimulated Raman scattering (SRS) spectroscopy of tetragonal Y_0.4Gd_0.6VO₄ vanadate crystals having a partly disordered zircon-type structure. Picosecond laser pumping revealed previously unexplored χ⁽³⁾-nonlinear interactions comprising the generation of an almost two-octave spanning Stokes and anti-Stokes frequency comb, self-third harmonic generation as well as cross-cascaded processes involving four different Raman-active modes. The recorded spectral lines have been assigned to the participating molecular vibrational modes of the (VO₄)^3- structural units of the studied crystal. In addition, this work provides a brief review of all known SRS-active tetragonal and monoclinic vanadates of the form REVO₄ including their χ⁽³⁾-nonlinear properties and steady-state Raman gain coefficients for first Stokes generation.

A. A. Kaminskii;J. Zhang;O. Lux;H. Rhee;H. J. Eichler;定元 汤;H. H. Yu;怀金 张;集旸 汪;H. Yoneda;A. Shirakawa

Laser Physics Letters

2014-12-1

We report on the experimental observation of period-doubling of randomly distributed multiple solitons in a passively mode-locked fiber laser. We show that after a period-doubling bifurcation, the period of each soliton in the cavity becomes doubled. However, the intensity variation of the solitons is not necessarily synchronized, indicating that their period-doubling is unrelated. Numerical simulations verified the experimental observations.

L. M. Zhao;定元 汤;T. H. Cheng;C. Lu

Optics Communications

2007-5-15

High quality holmium doped Yttrium Aluminum Garnet (YAG) transparent ceramics were fabricated by a reactive sintering method under vacuum. Fully dense Ho:YAG ceramics with the average grain size of ∼ 10 μm were obtained after vacuum sintering at 1780 °C for 8 h. The optical properties, microstructures and photoluminescence spectra of the fabricated Ho:YAG ceramics were investigated. The transmittances of Ho:YAG ceramic are higher than 82% at 400 nm and 84% at 2400 nm. The absorption coefficient was 1.32 cm^-1 for 1.5 at.% Ho:YAG at 1907 nm. And the absorption cross section of the Ho:YAG ceramic is 0.645×10^-20 cm².

Hao Yang;Jian Zhang;Xianpeng Qin;Dewei Luo;Jan Ma;定元 汤;Qitu Zhang

2012

5 at.% Yb:Y₂O₃ transparent ceramics were fabricated using vacuum sintering plus HIP. The ceramics doped with 1 at.% ZrO₂ as the sintering additive were densified at 1700 °C in vacuum followed by HIPing at 1775 °C, while those without sintering additives were densified at 1520 °C in vacuum followed by HIPing at 1450 °C. After sintering, both ceramics had relatively high in-line transmittance. However, during laser experiments, the ZrO₂-doped Yb:Y₂O₃ (Zr-YbY) ceramics were photodarkened when irradiated by 940 nm pump light. The discoloration might be attributed to the formation of Zr³⁺ color centers during lasing. In contrast, no photodarkening effect was detected in the pure Yb:Y₂O₃ ceramics without sintering additives (P-YbY). The P-YbY ceramics exhibited much higher lasing efficiency (17%) than the Zr-YbY ceramics (9%). To our best knowledge, it is the first time that the photodarkening effect was detected in rare-earth doped sesquioxide laser ceramics.

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

Journal of the European Ceramic Society

2019-2-1

The cw and femtosecond laser operations of Yb³⁺:CaYAlO ₄ (Yb:CYA) are demonstrated. The laser emitted a maximum cw power of 1:94 W with a slope efficiency (η_slope) of 71% and an optical-to-optical efficiency (η_opt) of 51%. Under mode-locking operation, the laser emitted near transform-limited pulses with 156 fs pulse width, 8:1 nJ pulse energy and 0:74 W average power. The η_slope and η_opt of the mode-locked laser were 37% and 20%, respectively.

W. D. Tan;定元 汤;X. D. Xu;D. Z. Li;J. Zhang;C. W. Xu;军 徐

Optics Letters

2011-1-15

Transparent YAG ceramics were fabricated by solid state reaction sintering using divalent dopants (CaO and MgO) as sintering additives without TEOS doping, and the effects of divalent dopants on their microstructure evolution and optical properties were investigated. It was found that CaO was more effective with respect to inhibiting grain growth than MgO, but not as effective as MgO in promoting densification. Fully dense, transparent YAG ceramics with excellent optical qualities could be achieved by optimizing the doping concentrations of CaO and MgO; the transmittance at 1064 nm was as high as 84.5% for 3 mm thick sample at the molar ratio of Ca: Mg=1:4, after sintered at 1840 °C for 8 h in vacuum.

Tianyuan Zhou;Le Zhang;Zheng Li;Shuai Wei;Jiadong Wu;Lixi Wang;Hao Yang;Zhenxiao Fu;Hao Chen;定元 汤;Chingping Wong;Qitu Zhang

Ceramics International

2017-2-15

A novel multiwavelength erbium-doped fiber laser (EDFL) based on a nonlinear high-birefringence fiber loop mirror (HiBi-FLM) is proposed and demonstrated. Up to 50-wavelength lasing operation with wavelength spacing of 0.8 nm has been achieved.

新焕 冯;H. Y. Tam;C. Lu;P. K.A. Wai;定元 汤

2007

Efficient dual-wavelength continuous-wave (CW) and passively Q-switched laser operation of Nd:(Gd_0.3Y_0.7)₂SiO₅ crystal were investigated for the first time to our knowledge. Maximum CW output power of 2.3 W was obtained under the absorbed pump power of 4.6 W, corresponding to the slope efficiency of 55%. Dual-wavelength CW laser with respective wavelengths around 1074 nm and 1078 nm were achieved. With Cr⁴⁺:YAG as the saturable absorber, passive Q-switched performance was obtained. The slope efficiency of passively Q-switched operation was 45%. The shortest pulse width, the corresponding pulse energy and peak power were calculated to be 13.1 ns, 50.2 μJ and 3.8 kW, respectively.

Xiaodong Xu;Juqing Di;Jian Zhang;定元 汤;军 徐

Optics Communications

2016-5-1