W. D. Tan

Mode locking of ceramic Nd:yttrium aluminum garnet with graphene as a saturable absorber

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.

Subpicosecond pulse generation from a Nd:CLNGG disordered crystal laser

We report on a diode-pumped passively mode-locked subpicosecond Nd:CLNGG disordered crystal laser for the first time to our knowledge. Owing to the large inhomogeneous broadening and spectrum splitting of the disordered crystal, the Nd:CLNGG laser generated 900 fs mode-locked pulses with a repetition rate of approximately 88 MHz at 1061 nm wavelength. With a single-emitter laser diode pumping, a maximum average output power of 486 mW was achieved with a slope efficiency of 26%. Our experimental results show that the four-level Nd:CLNGG disordered crystal could be an excellent alternative for subpicosecond pulse generation.

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.

Characterization of laser crystal Yb:CaYAlO 4

Yb:CaYAlO4 (Yb:CYA) crystals with good optical qualities have been grown by the Czochralski method. The detailed polarized spectral properties, including absorption and fluorescence, were investigated. The results reveal a broadband emission feature (FWHM=77 nm at σ polarization). The fluorescence lifetime has been measured using the powder concentration dilution method, and the intrinsic lifetime was found to be 426 μs. The thermal properties, including specific heat, thermal expansion, and thermal diffusion coefficients, have been investigated. The thermal conductivities were calculated to be 3.6 and 3.2 W/m/K along the a and c axes, respectively, at room temperature. The CW laser performances have been studied for both π and σ polarizations. The slope efficiencies of 55.4% and 41.4% were obtained for π- and σ-polarized operations, respectively. All the results show that Yb:CYA crystals should be excellent candidates as a laser medium for efficient and ultrafast lasers in the 1 μm region.

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 passively mode-locked Nd:CaNb2O6 laser

We have experimentally demonstrated a diode-pumped passively mode-locked Nd:CaNb2O6 laser for the first time to our best knowledge. With a semiconductor saturable absorber mirror (SESAM) as a passive mode locker, the laser generated stable mode-locked pulses with pulse duration of 17.3 ps and repetition rate of 88.4 MHz. With a singe-emitter laser diode pumping, the maximum average output power of the mode-locked laser was 0.843 W, with a slope efficiency of 23%. The experimental results show the Nd:CaNb2O6 crystal is a promising laser gain medium for picosecond pulse generation.

A highly efficient diode-pumped passively mode-locked Nd:Lu1.5Y1.5Al5O12 laser

In this letter, a diode-pumped passively mode-locked Nd:Lu1.5Y1.5Al5O12 (Nd:LuYAG) laser is demonstrated for the first time, to the best of our knowledge. With a semiconductor saturable-absorber mirror, a maximum output power of 0.85 W at 1064 nm was obtained under an absorbed power of 8.51 W, corresponding to a high slope efficiency of 44%. The mode-locked pulses were estimated to be 6.6 ps. The results of our experiment show that Nd:LuYAG crystal could be a promising material for diode-pumped ultra-short laser generation.

Highly efficient passive mode locking of Nd:Lu2.9Gd0.1Al5O12 garnet crystal

Passive mode locking of Nd:Lu2.9Gd0.1Al5O12 (Nd:LuGdAG) crystal lasers was experimentally investigated. Stable mode-locked pulses with pulse widths as short as 9.7 ps were obtained for the Nd:LuGdAG crystal; the corresponding maximum output powers were 0.93 W while the mode-locked slope efficiencies were 43%, among the highest efficiencies ever reported for Nd3+ ps lasers. The results demonstrate that Nd:LuGdAG garnet crystal is a promising gain medium for efficient picosecond laser use.

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.