第三讲-超短脉冲的产生教学文案.ppt

Lecture 3 Generation of ultrashort pulses ;The Metric System;Trotting Horse;Harold Edgerton MIT, 1942;时间尺度;The Generation of Ultrashort Laser Pulses;;Continuous vs. ultrashort pulses of light;Long vs. short pulses of light;For many years, dyes have been the broadband media that have generated ultrashort laser pulses.;Ultrafast solid-state laser media have recently replaced dyes in most labs.;But a light bulb is also broadband. What exactly is required to make an ultrashort pulse?Answer: A Mode-locked LaserOkay, what’s a laser, what are modes, and what does it mean to lock them?; What’s the real meaning of mode locking ;Mode locked principle ;Lasers modes: The Shah function;The Fourier transform of the Shah function;The Shah function and a pulse train;The Fourier transform of an infinite train of pulses;Generating short pulses = mode-locking;Locked modes;Numerical simulation of mode-locking;A generic ultrashort-pulse laser;Pulsed Pumping;Q-switching;Q-Switching;;What about the saturation intensity?;;Mode locked pulse formation ;;Passive mode-locking with a slow saturable absorber;Gain saturation shortens the pulse trailing edge.;Saturable gain and loss;A dye’s energy levels;The Passively Mode-locked Dye Laser;Some common dyes and their corresponding saturable absorbers;A lens and a lens;;;Modeling Kerr-lens mode-locking;Titanium Sapphire (Ti:Sapphire);Titanium Sapphire;Mechanisms that limit pulse shortening;The Ti:Sapphire laser including dispersion compensation;Commercial fs lasers;Very-short-pulse commercial fs lasers;;SESAM mode locking;SESAM parameters;CW mode locking threshold ;Ytterbium Tungstate (Yb:KGW) ;Active mode-locking;Gain switching;Synchronous pumping;Hybrid mode-locking;Commercial fs fiber lasers;Questions