Changwen Xu

Dual-wavelength passively mode-locked Nd:LuYSiO 5 laser with SESAM

A diode-end-pumped dual-wavelength mode-locked laser based on Nd:LuYSiO5 crystal is demonstrated. With a SESAM, simultaneous mode locking at the 1075.8 nm and 1078.1 nm is achieved and the dual-wavelength mode locked pulses have a pulse width of 8.9 ps. Due to frequency beating, ultrahigh repetition rate ultrafast pulses with 997 fs pulse width and 0.59 THz repetition rate are further formed. Under 12.7 W absorbed pump power 1.7 W mode-locked output power was obtained, the slope efficiency of the mode locked laser was 24.3%.

Femtosecond and continuous-wave laser performance of a diode-pumped Yb3+:CaYAlO4 laser.

The cw and femtosecond laser operations of Yb(3+):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.

Yb:LuAG laser ceramics: a promising high power laser gain medium

Yb:LuAG laser ceramics with different Yb3+ doping concentrations were successfully fabricated by using a solid-state reactive sintering method. SEM graphs demonstrate that the samples have a dense and pore-free microstructure. Based on the spectroscopic studies the ceramics have a large emission cross-section of 2.7 × 10−20 cm2 at 1030 nm emission peak. CW laser operation of the samples has given 7.2 W output power with 65% slope efficiency.

Comparison of the 1319 and 1338 nm Dual-Wavelength Emission of Neodymium-Doped Yttrium Aluminum Garnet Ceramic and Crystal Lasers

The 1319 and 1338 nm dual-wavelength operation of neodymium-doped yttrium aluminum garnet (Nd:YAG) ceramic and single-crystal lasers was experimentally compared. It was found that, although the single-crystal lasers preferably to oscillate at 1319 nm under strong pumping, the ceramic lasers tend to operate at 1338 nm, indicating the existence of a subtle difference between the 4F3/2–4I13/2 transitions of the Nd3+ ions in the Nd:YAG crystal and ceramic lasers.

Highly efficient continuous-wave Nd:YAG ceramic lasers at 946 nm

Highly efficient CW operation of diode-end-pumped Nd:YAG ceramic lasers at 946 nm is experimentally demonstrated. When a 5 mm long in-house fabricated Nd:YAG ceramic was used as the gain medium, a maximum output power of 10.5 W was obtained under an incident pump power of 35 W, corresponding to an optical conversion efficiency of 30%, while, when a 3 mm long ceramic sample was used, a maximum output power of 8.7 W was generated with a slope efficiency of 65% with respect to the absorbed pump power. Both the optical conversion efficiency and slope efficiency are the highest results reported so far for the diode-pumped 946 nm lasers.

Evidence of dissipative solitons in Yb 3+ :CaYAlO 4

Operation of an end-pumped Yb³⁺:CaYAlO₄ laser operating in the positive dispersion regime is experimentally investigated. The laser emitted strongly chirped pulses with extremely steep spectral edges, resembling the characteristics of dissipative solitons observed in fiber lasers. The results show that dissipative soliton emission constitutes another operating regime for mode locked Yb³⁺-doped solid state lasers, which can be explored for the generation of stable large energy femtosecond pulses.

Diode-pumped femtosecond Yb:CaNb2O6 laser

We report to our knowledge a diode-pumped passively mode-locked Yb:CaNb(2)O(6) (Yb:CN) laser for the first time. Both CW and passive mode-locking operation of the laser are experimentally investigated. A maximum CW output power of 1.4 W with a slope efficiency of 20% is obtained on a 7 mm long 1.5 at.% Yb:CN crystal, while stable passive mode-locking with a commercial semiconductor saturable absorption mirror (SESAM) was achieved on a 3 mm long 3 at.% Yb:CN crystal. The mode-locked pulses have pulse width of 251 fs and an average output power of 44 mW at 1038 nm.

Mode locking of Yb:GdYAG ceramic lasers with an isotropic cavity

We report on the passive mode locking of a diode pumped Yb:GdYAG ceramic laser with a near isotropic cavity. It is found that the laser could simultaneously mode lock in the two orthogonal principal polarization directions of the cavity, and the mode locked pulses of the two polarizations have identical features and are temporally perfectly synchronized. However, their pulse energy varies out-of-phase periodically, manifesting the antiphase dynamics of mode locked lasers.

Passive mode-locking performance of mixed Nd:La(0.11)Y(0.89)VO(4) crystal.

Passive mode locking of a diode pumped Nd:La(0.11)Y(0.89)VO(4) mixed crystal laser with a semiconductor saturable absorber mirror (SESAM) was experimentally investigated for the first time to our knowledge. Stable CW mode-locking has been achieved on both a-cut and c-cut mixed crystals. In case of the a-cut crystal, when a 2% output coupler (OC) was used, the shortest pulse obtained was 4.5 ps and the highest output power was 0.94 W, while when a 6% OC was used, the shortest pulse obtained was 6.8 ps and the highest output power was 5.16 W. In the latter case the optical conversion efficiency is 38% and the slope efficiency is 40.3%, respectively; with the c-cut crystal the shortest pulse achieved was 5.5 ps. Moreover, simultaneous mode locking at two close wavelengths of 1064.3 nm and 1066.2 nm was observed on the c-cut crystal. The mode locked pulse beating generated temporal interference fringe of 0.5 THz repetition rate.

Dark pulse emission from a 780nm diode laser with external cavity feedback

Dark pulse emission from a 780nm diode laser was observed. The laser consists of a simple laser diode module and a planar mirror. The obtained maximum output power for dark pulse operation is 97mW. But the duration and darkness of the pulses, as well as the formation mechanism need to be confirmed.