Study On Propagation Properties Of The Ultrashort Pulse In Nd: Glass Amplifying Medium

Amplifier is a important part that produces high power ultra- short puls. So it is a very important theme to study amplifying propagation and properties of this pulse in amplifying medium.In this paper, after considering Kerr nonlinear effect,group velocity dispersion of host,gain spectrum,gain saturation of amplifying medium and frequency fluctuation of optic pulse. The propagation characteristics of chirped in Nd³⁺: glass laser amplifying medium has been researched, the results can provide some theoretical gist for further advantage and pulse shaping of amplifier .The main works of paper are as follows:1. From the Maxwell's equations,the basic epuation, the nonlinear paraxial equation of slow varying amplitude of optical pulse in amplifying medium has been deduced, and obtain two desription methods.Furthmore, the gain property, group velocity dispersion property and Kerr nonlinear effect property of Nd³⁺: glass amplifying medium have been analyzed in detail.2. By using the Fourier transformation method, we researched the propagation characteristics of pulse shape , frequency spectrum phase shift of a ps super-Gaussion pulse in Nd³⁺: glass laser amplifying medium length whenω₀ isω_g ,and discussed the influence of dispersion,gain spectrum,gainsaturation and nonlinear effect of medium to them.The numerical calculations and analysis show that, The dispersion and the gain spectrum of ps optical pulse in the medium can be ignored, but the Kerr nonlinear effect and the gain saturation will change shape of the pulse.The Kerr nonlinear effect will change the spectrum of the pulse together with the gain saturation.3. The influences of frequency fluctuation to pulse shape has been analyzed,and numerical calculations has been down to it by using Fourier transformation method. The results show that the intensity of optical pulse decreases as its frequency fluctuation increases. The frequency fluctuation will change the evenness of pulse together with chirp parameter. This is the same or opposite compared with the gain saturation. And it also provides certain theoretical for pulse shaping of amplifier.