Passive Tuning Q Optimization Analysis And The Effect Of Passive Tuning Q Laser Collision

From the history, all scientific inventions or discoveries are nothing more than tworoads: one is existing in nature, when people consciously or unconsciously found andlater produce theory, and tries to prove and use, such as gravity, oxygen,electromagnetic, etc, this kind of situation is called "scientific discoveries"; the Secondis (at least does not exist on earth), but people deduce theoretically, first predict, thenprove it and implementation, through efforts such as relativity, nuclear decay, nuclearfusion, this situation is referred to as "scientific discoveries". While the latter is morescientific and theoretical and challenging, the birth of laser process is belong to the latter.Laser is the20th century, following the atomic energy, computers, semiconductors, afteranother great invention of human beings.In the first twenty years of the birth of laser, the pumping system are adopted bythe krypton lamp or hernia lamp, the efficiency of this kind of laser is low, and theworking life is short. In the year of1978, the concept of quantum-well semiconductorlaser was put forward, which provide much more possibility for the laser toward adirection of more powerful longer life expectancy and lower energy consumption.Fromthen on, LD pump laser(or the second generation laser)began to boarded the stage ofhistory. LD pumped laser, with its long working life, high light conversion efficiencyand the volume of a mini gradually replaced the traditional laser, in health,optoelectronic industry and plays an important role in national defense.In this paper, Nd:YAG/Cr:YAG is used as the laser gain medium, and a theoryanalysis is made on the passively Q-swiched laser output characteristics which waspumped by the LD.A new concept called Collision effect theory was proposed,and thenwe conduct an experiment using the FAP-systemTMsemiconductor laser fiber couplingoutput produced by Coherent companies in the United StatesThe main content includes the following aspects:1. Review the development history and status quo of laser.2. A simple introduction is made about Q-swiched theory, including the type ofQ-swiched laser, the rate equation theory on passively Q-swiched laser, and acalculation on peak power, output energy and pulse width is made. 3. A simple introduction on Saturable absorption features of Cr:YAG is made.4. A optimizing analysis is made on passively Q-swiched laser. The absorbing andcoupling parameters are derived by Lagrange multiplier method, and we plot theabsorbing and coupling parameters against a dimensionless variable z.5. The collision effect is regarded as a thermal loss in the process of Q-swichedlaser, and a proper modification on rate equation is made with the introducing ofcollision loss factor. Numerical analysis and experiment contrast are made on laseroutput parameters under the instance of Nd:YAG/Cr:YAG. From the numerical analysiswe can draw a conclusion that since the influence of collision effect is different in thedifferent part of the rod, the building time of pulse is different. So the pulse width isnarrower than the actual value. Low pumping power on pulse energy and peak powerinfluence is bigger, when the pulse power increases, the corresponding impact will beweakened.