飞秒激光刻写铌酸锂光波导的实验研究

研究了飞秒激光加工参量对刻写质量的影响,分析了激光能量吸收的多光子效应,测试了刻写通道的传输特性.实验结果表明,激光刻写的通道具有良好的波导特性：当激光脉冲能量在20 μJ左右,扫描速度在300 μm/s～400 μm/s之间时,刻写通道的传输损耗小于1 dB/cm,低于晶体的传输损耗,其原因是激光诱导锂离子的扩散引起了晶体内部局部折射率的增加.     

自相似抛物脉冲光纤放大器中超短脉冲的演化特性

采用色散长度、非线性长度和增益系数作为自相似抛物脉冲光纤放大器的特征参量,用分步傅里叶方法数值模拟了输入超短脉冲在光纤放大器中的演化规律.研究了色散长度和非线性长度对脉冲自相似演化的影响,获得了放大器中脉冲实现自相似演化的条件.研究了增益系数对脉冲自相似演化的形成和放大传输的影响,发现增益系数可以影响脉冲的演化进程和结果.     

Pulse Evolution Characteristics in Self-Similar Mode-locked Fibre Laser

A self-similar mode locked fibre laser is studied based on a numerical model. By introducing a dimensionless factor k to characterize the pulse shape, the self-similar pulse evolution, formation and the temporal and spectral shape changes due to the elements in the cavity are investigated throughout the laser cavity. The results show that in the self-similar mode locked fibre laser, self-similar pulse is first formed in the single-mode fibre, which is then amplified in the gain fibre. Gain bandwidth has a small influence on pulse shape, so high energy self-similar pulse can be obtained after amplification. Because net cavity dispersion directly influences the pulse width as well as peak power after compression by a pair of gratings, which can determine the pulse self-similar evolution, it is very important to control the net cavity dispersion to a certain range to obtain self-similar pulses.     

S-Band Gain-Flattened Double-Pass Discrete Fibre Raman Amplifiers Using Mechanically Induced Long-Period Fibre Gratings

We experimentally demonstrate an S-band double-pass （DP） discrete fibre Raman amplifier （FRA） gain-flattened by using a mechanically induced long-period fibre grating （LPFG）. Due to a photo-elastic effect in the fibre and its peak loss, the wavelength and depth of the mechanically induced LPFG are continuously regulated by varying the pressures, the angle of the fibre on the graphite rods which are used to produce the periodical pressures along the fibre, the number and the diameter of the graphite rods. Using this gain flattening filter, the gain profile of the DP-FRA is flattened to within ±0.8 dB in the wavelength range from 1485 nm to 1525 nm.     

飞秒脉冲初始脉宽和啁啾对其自相似演化及压缩的影响

采用自相似抛物脉冲放大器对飞秒脉冲直接进行放大,并以低非线性系数的光子带隙光纤作为脉冲压缩器对放大的脉冲进行压缩.通过分步傅里叶方法研究了飞秒脉冲的初始宽度和啁啾对其自相似演化和压缩的影响.研究结果表明脉冲宽度越宽,脉冲自相似演化程度越差,演化脉冲的压缩质量也越差,压缩脉冲宽度较大,且有基座;脉冲的初始啁啾会严重阻碍其自相似演化,并最终影响脉冲的压缩质量;啁啾越大,脉冲的自相似演化结果越差,脉冲的压缩质量也越差;正的啁啾对脉冲的自相似演化的影响比负啁啾的要大.     

高能量无波分裂超短脉冲自相似传输的理论研究和数值模拟

从非线性薛定谔方程出发，对SPM作用引起传输脉冲的相位作了合理近似，引入了频谱展宽因子，发现在存在增益时正色散光纤的SPM作用加剧了脉冲频谱展宽幅度，并且脉冲中心和两翼部分的频谱展宽差异很大.给出了存在增益的正色散光纤中高斯型脉冲自相似传输的时域演化，揭示了脉冲展宽的中心部分对边翼部分挤压和覆盖及最终形成自相似脉冲的过程，提出了自相似传输现象的一种合理解释.并通过数值模拟三种不同形状初始脉冲的自相似演化过程对提出的理论进行了验证.