Visiting Fellowship for Professor E.P. Ippen

这项资助申请是为了资助麻省理工学院Erich Ippen教授到伦敦帝国理工学院飞秒光学小组的访问奖学金，以便开展一项关于光纤激光器和无源光纤器件中飞秒脉冲产生和动力学的合作研究计划。Ippen教授是世界上在超短脉冲的产生、表征和应用方面的领先专家之一。其中一种最新的光纤激光器以铋作为激光作用的活性离子，与其他稀土掺杂的硅基光纤相比，它在广泛的荧光范围或增益分布方面是独一无二的。因此，可以使其在远程通信应用中具有吸引力的宽光谱轮廓也能够支持超短脉冲。Ippen教授是世界领先的被动锁模技术专家，在被动锁模技术中，各种元素(可饱和吸收体)的引入使强度相关的传输进入激光腔，导致自由运行激光表面上随机输出的超短脉冲的演化和自同步。最初可饱和的吸收体是有机染料，然而，目前正在研究的固态器件，如半导体或悬浮在纤维素膜中的单壁碳纳米管。这两种方法将被用来研究掺铋石英光纤和掺铊石英光纤中飞秒脉冲的产生。后者还将与级联高功率光纤放大器一起使用，以产生高平均和高峰值功率脉冲，用于在氟化物光纤中产生超宽波长连续谱，覆盖中红外从2到5微米。还将研究光纤中超连续谱的基本形成机制，并研究噪声对超连续谱动力学和长波增强的作用。

This grant application is made for funds to partially support the Visiting Fellowship of Professor Erich Ippen from MIT to the Femtosecond Optics Group at Imperial College London in order to undertake a collaborative research programme on femtosecond pulse generation and dynamics in fibre lasers and passive fibre devices. Professor Ippen is one of the world's leading experts on the generation, characterization and application of ultrashort pulses.One of the newest fibre lasers has Bismuth as the active ion for laser action and compared to other rare earth doped silica based fibres it is unique in the broad extent of its fluorescence or gain profile. Consequently, the broad spectral profile, which could make it attractive for telecomunications applications is also capable of supporting ultrashort pulses. Professor Ippen is the world's leading expert on passive mode locking techniquies, where the introduction of various elements ( saturable absorbers) that exhbit an intensity dependent transmission into the laser cavity, lead to the evolution and self synchronization of ultrashort pulses from the apparently random output of the free running laser. Originally the saturable absorbers were organic dyes, however, currently solid state devices such as semiconductors or single walled carbon nanotubes suspended in cellulose films are currently being investigated. Both of these wioll be used to investigate femtosecond pulse generation in bismuth doped silica fibre and also thullium doped silica fibre. The latter will also be employed in conjunction with cascaded high power fibre amplifiers to generate high average and high peak power poulses that will be used to generate an ultrabroad continuum of wavelengths in fluoride based fibre that will cover the mid infra red from 2 to 5 microns.The basic formation mechanism of the supercontinuum in optical fibre will also be investigated and the role of noise both on the dynamics and on the long wavelength enhancement of the supercontinuum will be examined.