基于铋可饱和吸收体的超快激光产生

采用磁控溅射沉积法在微纳光纤表面上镀一层纳米级厚度的铋薄膜,制备了一种微纳光纤-铋膜结构的可饱和吸收体.在1.5μm处的非线性光调制深度为14%.将其应用到掺铒光纤激光器中,在1.5μm波段获得稳定的超快脉冲激光产生,脉宽为357 fs,输出功率为45.4 mW,单脉冲能量为2.39 nJ,信噪比为84 dB.实验结果表明,利用磁控溅射法可制备出大调制深度的可饱和吸收体,为获得高能量超短脉冲激光输出提供新方案.

Generation of ultra-fast pulse based on bismuth saturable absorber

We demonstrate a bismuth(Bi) saturable absorber(SA) for generating ultrafast pulse. The Bi SA is fabricated by the Bi film deposited on the surface of microfibers through using magnetron sputtering. Its nonlinear optical properties are investigated. The as-prepared Bi SA has outstanding nonlinear absorption property demonstrated by the open aperture(OA) Z-scan system at 1500 nm and balanced twin-detector method at 1560 nm. The nonlinear optical property of Bi SA shows that the modulation depth, the nonsaturable losses, and the saturable intensity at 1.5 μm are 14% and 79%, and 0.9 MW/cm2, respectively.Besides, the closed aperture(CA) Z-scan measurement is also implemented to estimate the nonlinear refractive index of Bi film. The Bi film shows that the typical CA/OA curve possesses the feature of peak-valley profile,meaning that the sample with a negative nonlinear refractive index is self-defocusing. In our experiments, the parameters of the nonlinear absorption coefficient b and the nonlinear refractive index n2 are estimated at about2.38 × 10-4cm/W and –1.47 × 10^-9 cm^2/W according to the actual experimental data points, respectively. To further investigate its nonlinear optical property, the microfiber-based Bi SA is embedded into an erbium-doped fiber laser with a typical ring cavity structure. Based on the Bi SA device, the stable ultrafast pulses are generated at 1.5 μm with the pulse width of 357 fs, the output power of 45.4 mW, corresponding to the pulse energy of 2.39 nJ, and the signal-to-noise ratio is 84 dB. The stable soliton pulses emitting at 1563 nm are obtained with a 3-dB and 6-nm spectral bandwidth. The experimental results suggest that the microfiber-based Bi SA prepared by magnetron sputtering deposition(MSD) technique can be used as an excellent photonic device for ultrafast pulse generation in the 1.5 μm regime, and the MSD technique opens a promising way to produce high-performance SA with a large modulation depth, low saturable intensity, and high power tolerance,which are conducible to the generation of high power and ultrafast pulse with high stability.