MacLeod AM, Yan X, Gillespie WA, Knippels GM, Oepts D, Rella CW, Smith TI, Schwettman HA
School of Science and Engineering, University of Abertay Dundee, Bell Street, Dundee DD1 1HG, United Kingdom.
Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics. 2000 Sep;62(3 Pt B):4216-20. doi: 10.1103/physreve.62.4216.
The detailed shape of picosecond optical pulses from a free-electron laser (FEL) oscillator has been studied for various cavity detunings. For large values of the cavity detuning the optical pulse develops an exponential leading edge, with a time constant proportional to the applied cavity detuning and the quality factor of the resonator. This behavior has been observed at two separate FELs that have completely different resonator layouts and electron beam characteristics, and using different methods of optical pulse length measurement. The optical pulses have a full width at half maximum time-bandwidth product Deltat(FWHM)Deltaf(FWHM) of 0.2-0.3. The results presented here can be used to predict the optical pulse length and corresponding minimum spectral width that can be generated in a FEL pumped by short electron bunches. This is important for the design of new infrared free-electron laser user facilities, which need to make a balanced choice between short pulses for high temporal resolution and narrow bandwidth for linear and nonlinear spectroscopy.
针对各种腔失谐情况，对自由电子激光（FEL）振荡器产生的皮秒光脉冲的详细形状进行了研究。对于较大的腔失谐值，光脉冲会形成指数上升沿，其时间常数与施加的腔失谐以及谐振器的品质因数成正比。在两个具有完全不同谐振器布局和电子束特性的独立FEL上，采用不同的光脉冲长度测量方法，均观察到了这种行为。光脉冲的半高全宽时间 - 带宽积Δt（FWHM）Δf（FWHM）为0.2 - 0.3。此处给出的结果可用于预测由短电子束团泵浦的FEL中能够产生的光脉冲长度以及相应的最小光谱宽度。这对于新型红外自由电子激光用户设施的设计很重要，因为这些设施需要在用于高时间分辨率的短脉冲与用于线性和非线性光谱学的窄带宽之间做出平衡选择。
