The chirp effect in supercontinuum (SC) generation in photonic crystal fibers (PCFs) is researched carefully in experiment. Using an acoustic-optics programmable dispersive filter (AOPDF), the 1-4 order dispersions of the pulses from femtosecond oscillator can be accurately controlled. The experimental results show the SC generation in PCF is sensitive to the chirp of incident pulse, and the output spectrum and conversion efficiency can be tuned by changing the initial dispersion state. With different group delay dispersion (GDD) brought to the incident pulse, we find that positive chirp can enhance the energy conversion to long wavelength, and negative chirp can enhance the conversion to short wavelength. Specially, an optimal negative chirp can maximize the conversion to the shortest one at about 625 nm. The effect of the third-order dispersion (TOD) also has been investigated, and we find that the same value of the positive and negative TOD has the similar effect on the SC.

We describe a Ti:sapphire multi-pass amplifier with high efficiency at the repetition rate of 1 kHz. In the amplifier, the incident pulse is 0.66 mJ with the pulse duration about 90 ps. The incident pulse is amplified to 7.2 mJ when the pump energy is 23 mJ. The energy efficiency in the amplifier is nearly 30% with extracting efficiency larger than 40% when considering about 25% static reflecting loss in the amplifier. After compressed in the compressor, 5.4-mJ, 36-fs pulses with peak power larger than 0.1 TW are obtained.

为了使得数值模拟更为精确, 采用广义非线性薛定谔方程(GNSE)描述超短激光脉冲在光子晶体光纤中的传输演化过程, 并利用二阶分步傅里叶方法通过求解方程, 数值计算了相同脉宽和能量的超短脉冲在不同色散参量的光子晶体光纤中非线性传输和超连续谱的产生。比较了超短脉冲在光纤不同色散区传输时, 高阶色散和非线性效应对超连续谱的产生以及对脉冲波形演化的影响。结果表明, 相对于超短脉冲中心波长位于光子晶体光纤的正常和反常色散区, 可以相应获得短波波段和长波波段的超连续谱输出, 当超短脉冲中心波长位于零色散波长点时, 通过色散和非线性效应的联合作用, 更易于产生全波长段的平坦超连续谱。

The effects of gain narrowing and high order dispersions on the pulse duration in our kilohertz chirped-pulse amplification system have been compensated experimentally. Using an acousto-optic programmable dispersive filter (AOPDF), the spectral full-width at half-maximum (FWHM) is expanded from 30 to 50 nm. Stable laser pulses with the duration of 30 fs (FWHM), which is 1.07 times Fourier-transform-limitation, have been acquired by pre-compensating the high order phase distortions using the phase measured by spectral phase interferometry for direct electric-field reconstruction (SPIDER).

为扩展可调谐TEA CO2激光器的输出波长范围,增加差分吸收雷达可探测的物质种类,采用13C16O2代替激光器工作气体中的CO2成分。计算了TEA13C16O2激光器在Ⅰ波段两个分支上的小信号增益系数分布。利用平面光栅单色仪,在小型快调谐TEA13C16O2激光器的Ⅰ波段共测到了32条谱线的能量输出,输出范围为10.663～11.347 μm。与采用普通CO2作为工作气体的情况相比,激光器谱线输出范围在长波长方向上有很大扩展,输出的最长波长由CO2的10.74 μm增大到11.347 μm。测得TEA13C16O2激光器的最高输出能量为107 mJ,并给出了Ⅰ波段典型谱线脉冲的半峰全宽。

谐波振子数学模型是TEACO2激光振动动力学的一种表述,它是对复杂温度模型的一种简化.以四个特征变量表征CO2的三个振动态和N2分子的振动态的能量变化,把激光腔内输出光强、光通量、气体温度与四个特征变量随时间变化率相联系,建立数学方程.改变激光器各种参量,可计算得到其对脉冲波形的影响.由激光光强,可求得激光输出功率和能量,为激光器的优化设计提供重要的理论依据.经过实验验证,理论计算值与实验结果基本相符.

利用衍射光栅方程,分析可见光谱区标准光源的特征谱线的多级衍射特征,对标准光源的多级衍射进行计算机模拟计算,确定其多级衍射光强分布.测量汞灯特征谱线和He-Ne激光谱线的多级衍射谱分布,确定多级衍射谱的各级级次.对所得数据处理,做出拟合曲线,以多项式拟合方法求得拟合方程.以连续CO2激光器输出激光进行检测,同时以谱线分析仪监测,经过测量其波长,验证红外光栅单色仪定标准确.