Raman光激射器

本文从哈密顿量出发,导出描写受激Raman过程的方程式:Laser光、一级Stokes与反Stokes光及相干的声子场的耦合方程,并唯象地引入弛豫耗散。在分子属于远共振情形及比介电常数近似更高一级的近似下,分析了方程的性质。由平衡点稳定性的讨论给出了Raman光激射器的阈值,发现反Stokes激射光的产生并不要求附加的阈条件,即在受激Raman效应中,反Stokes光总是必然出现的。对于Raman光激射器诸工作点的性质及工作过程也作了进一步的讨论,发现在一定条件下,在强激射光源辐照下,存在着Stokes与反Stokes成分几乎各占一半的唯一的稳定平衡点(Raman光激射器的工作点)。文中也顺便讨论了声子弛豫所起的作用及有长寿命的声子时Raman光激射器的行为。

ON THE THEORY OF RAMAN MASERS

In this article, the coupling equations of the laser, the first Stokes, the first anti-Stokes light, and the coherent phonon field are derived from the hamiltonian with the relaxation and dissipation terms introduced phenomenologically. The properties of these equations are analysed by adopting an approximation higher than the quasi-static approximation, provided the molecules are far from resonance. The threshold for a Raman Maser is obtained and the temporal behaviour discussed. It is shown that no additional threshold condition is required for the anti-Stokes components, i.e., the stimulated anti-Stokes radiations make their appearance as a matter of fact in the stimulated Raman effect. Under certain conditions, there exists only one stable equilibrium point, at which the Stokes and anti-Stokes light appear with equal intensity, when the Raman-active medium is pumped by an intensive laser beam. The effect of phonon relaxation and the behaviour of the Raman Maser with long lifetime phonons are discussed as well.