Lucht Robert P, Roy Sukesh, Gord James R
School of Mechanical Engineering, Purdue University, West Lafayette, Indiana 47907-2088, USA.
J Chem Phys. 2004 Nov 22;121(20):9820-9. doi: 10.1063/1.1809572.
The physics of the two-photon absorption process is investigated for a three-state system. The density-matrix equations for the two-photon interaction are solved in the steady-state limit assuming that the pump laser radiation is monochromatic. Collisional broadening, saturation, and Stark shifting of the two-photon resonance are investigated in detail by numerical solution of the steady-state density-matrix equations. Analytical expressions for the saturation intensity and the Stark shift are derived for the case where the single-photon transitions between the intermediate state and the initial and final states are far from resonance with the pump laser. For this case, it is found that the direction of the Stark shift is dependent on the relative magnitudes of the dipole-moment matrix elements for the single-photon transitions that couple the intermediate state with the initial and final states. Saturation and Stark shifting are also investigated for the case where the single-photon transitions between the intermediate state and the initial and final states are close to resonance with the pump laser.
针对一个三态系统研究了双光子吸收过程的物理特性。假设泵浦激光辐射是单色的，在稳态极限下求解了双光子相互作用的密度矩阵方程。通过稳态密度矩阵方程的数值解详细研究了双光子共振的碰撞展宽、饱和及斯塔克频移。对于中间态与初态和末态之间的单光子跃迁与泵浦激光远失谐的情况，推导了饱和强度和斯塔克频移的解析表达式。对于这种情况，发现斯塔克频移的方向取决于将中间态与初态和末态耦合起来的单光子跃迁的偶极矩矩阵元的相对大小。对于中间态与初态和末态之间的单光子跃迁与泵浦激光接近共振的情况，也研究了饱和及斯塔克频移。
