Absorption and Raman Scattering of Light

V. A. Zubov, M. M. Sushchinskiǐ, I. K. Shuvalov

Joachım Herrmann

Abstract A review of the theory of the stimulated resonance Raman scattering (SRRS) is given. The calculation of the gains for the SRRS with the ground level (SRRS I) or an excited one (SRRS II) as initial states shows that there are some restrictions for their appearance. Due to the strong resonance absorption of the pumping wave and the disturbing influence of stimulated fluorescence the SRRS I is not observable in a Franck‐Condon excitation and in an absorption of Lorentzian line shape. The SRRS II has a sufficiently large gain on the condition τel ≪vib (τel, τvib – transversal relaxation time of the electronic or vibronic transition). In case of a strong deviation of the wings of the absorption profile from the Lorentzian shape, however, the SRRS I is favoured rather than the two other processes. Another possibility to avoid the resonance absorption of the pumping wave exists for the transversal excitation of the SRRS. Thereby the limit of application of the SRRS may be extended to other substances which are no saturable absorbers. Apart from the saturable absorption and the transversal excitation the self‐induced transparency is the third possibility to generate SRRS of ultrashort light pulses.

D. Cotter, Richard R. Wyatt

The small-signal theory of transient stimulated Raman scattering is extended to include the effects of focusing, diffraction and absorption losses for both the pump and scattered Stokes light. There is good quantitative agreement between the predicted and experimentally observed threshold for stimulated electronic Raman scattering in caesium vapour with picosecond laser pulses.

P. P. Shorygin

G V Venkin, Iu. A. Il'Inskii, A. S. Mkoyan

Dilip Kumar Giri, Partha Sarathi Gupta

The non-classical effects of squeezing of light in coherent anti-Stokes Raman scattering (CARS) and coherent anti-Stokes hyper-Raman scattering (CAHRS) are investigated under the short-time approximation based on a fully quantum mechanical approach. In an idealized model CARS, the interaction is looked upon as a process involving absorption of a pump photon and emission of a Stokes photon, which is followed by absorption of a pump photon and subsequently emission of an anti-Stokes photon at a different frequency, whereas CAHRS is looked upon as a process involving absorption of two pump photons and emission of a Stokes photon, which is followed by absorption of two more pump photons and subsequent emission of an anti-Stokes photon at a different frequency. The coupled Heisenberg equations of motion involving real and imaginary parts of the quadrature operators are established. It is shown that squeezing in the Stokes and anti-Stokes mode in CARS is found to be dependent on amplitude-squared squeezing of the initial pump field while, in CAHRS, it is dependent on the fourth-order amplitude squeezing of the initial pump field. Higher-order squeezing can be converted to linear squeezing through these processes. It is also shown that squeezing is greater in CAHRS than the corresponding squeezing in CARS.