Phase-Dependent Lineshape in Multiple Pump-Probe Interactions

M. Ducloy, Daniel Bloch

We present in this paper a theoretical study of the angular dependence of phase-conjugate emission via resonant degenerate four-wave mixing (FWM) in Doppler-broadened gas media. The nonlinear optical polarization is calculated through an expansion of the atomic density matrix up to the third order in the incident fields. One finds that, when the incident frequency is resonant for a single-photon transition, both strength and lineshape of the phase-conjugate emission strongly depend on the angle 0 between standing pump wave and probe wave. The emission intensity, maximum at grazing incidences, decreases rapidly by several orders of magnitude when 0 increases. Simultaneously the emission linewidth increases from homogeneous to Doppler width. Similar effects are predicted for nearly-degenerate FWM (different pump and probe frequencies). In particular, one shows that the bandwidth of the equivalent optical reflection filter undergoes a Doppler-broadening linearly increasing with sin θ. On the opposite, none of the above effects is predicted in two-photon-resonant FWM which does not exhibit any angular dependence.

J.-P. Likforman, M. Joffre, Daniele Hulin

Manoj Kumar, Joseph H. Eberly

We present results on transient lineshapes in signals generated coherently via the nonlinear mixing of pump and probe fields in a model two-level system. We confine ourselves to times short compared to atomic relaxation times and hence treat both fields nonperturbatively. However, the probe is assumed to be much weaker than the pump. Transient lineshapes have been studied earlier in the case of atomic relaxation times and hence treat both fields nonperturbatively. However, the probe is assumed to be much weaker than the pump. Transient lineshapes have been studies earlier in the case of atomic inversion. Here, we identify the lineshape with the intensity of the light scattered in a particular direction and around a particular central frequency. The lineshapes are found to exhibit, in the neighbourhood of subharmonic resonances, highly non-lorentzian profiles.

V. L. Jacobs

Harry Friedmann, A. D. Wilson‐Gordon

Pressure‐ and radiation‐induced stimulated Rayleigh scattering in the Rayleigh wing are discussed quantitatively for the case where both the pump laser at fixed frequency ω1 and the probe laser with variable frequency ω2 are arbitrarily strong. The absorption spectra of the pump and probe fields, both expressed as a function of ω2, exhibit a narrow dispersive lineshape centered at the fixed frequency ω1 but with opposite tendencies: the field whose frequency is closest to the resonance frequency, ωba, of the two‐level system always undergoes stimulated emission, the other field being absorbed. The intensity of these processes increases, up to a limit, with the intensity of both the pump and probe fields. A qualitative explanation for the origin of the dispersive lineshape is suggested.

Alexander F. Kemper, Michael A. Sentef, Brian Moritz +1 more