基于色散管理的自相位调制光谱展宽滤波技术

Dispersion management dual-pass self-phase modulationenabled spectral selection

自相位调制光谱滤波技术能够产生波长可调谐的飞秒脉冲,有望取代传统复杂的光参量振荡器而受到关注.然而,光纤中的正色散会导致光谱旁瓣调制深度减小,同时光波分裂现象阻碍了光谱的展宽.为了解决这两个问题,本文提出了一种基于色散管理的双通光谱滤波技术,在脉冲演化过程中通过引入负色散来优化脉冲的前后沿形状,并压缩脉冲宽度以提升脉冲的峰值功率,所产生的光谱不仅旁瓣更加清晰,而且调制深度更深.使用2 cm LMA-8光纤,利用该技术获得了脉冲能量为6 nJ、中心波长在920 nm的113 fs脉冲.

Self-phase modulation-enabled spectral selection(SESS)technology can generate wavelength-tunable femtosecond pulses,and it is expected to replace traditional complex optical parametric oscillators,and thus has attracted much attention.However,the positive dispersion in the fiber leads the modulation depth of the spectral lobes to decrease,while optical wave breaking hinders the spectral broadening.In order to solve the two problems,we propose a dual-pass SESS technology based on dispersion management which optimizes the shape of the front edge and rear edge of the pulse prior to the second pass by introducing negative dispersion,and compresses the pulse width for increasing the peak power of the pulse.The resulting spectrum features broader spectrum with a deeper modulation depth.By numerical simulation,we find that adjusting the value of the second-order dispersion compensated after the single pass,a broader spectral lobe can be obtained than both the single-pass case and the double-pass case without dispersion compensation.To verify our numerical simulation,we conduct experiments by using a 2-cm-long LMA-8 fiber for spectral broadening and several chirped mirrors to provide negative dispersion,which controls the nonlinear evolution of the pulse in the second pass of the LMA-8 fiber.We study the spectral output corresponding to different amounts of dispersion compensation and find that an optimal dispersion value is required to produce a clear and broader spectral lobe.We also investigate the effect of input pulse energy on spectral broadening under the same dispersion compensation conditions.With 15-nJ input pulse energy and–420 fs^(2) dispersion compensation,the resulting SESS source delivers 6 nJ,113-fs pulses with the peak wavelength at 920 nm.