Efficient Raman sideband generation in a coherent atomic medium

Abstract

We demonstrate the efficient generation of Raman sidebands in a medium coherently prepared in a dark state by continuous-wave low-intensity laser radiation. Our experiment is performed in sodium vapor excited in Λ configuration on the D1 line by two laser fields of resonant frequencies ω1 and ω2, and probed by a third field ω3. First-order sidebands for frequencies ω1, ω2 and up to the third-order sidebands for frequency ω3 are observed. The generation starts at a power as low as 10 microwatt for each input field. Dependencies of the intensities of both input and generated waves on the frequency difference (ω1 − ω2), on the frequency ω3 and on the optical density are investigated.42.50. Gy, 32.80.Qk, 42.50.Hz

Phase Correlation of Laser Waves with Arbitrary Frequency Spacing

“…3(a): As ω 1 and ω 2 propagate, more and more lower noise frequencies ω become correlated, and ∆S 12 (τ ) exponentially decreases and asymptotically approaches the limit set by Γ. The curve ∆S 12 (τ ) was fitted by an exponential decay function yielding a dark state coherence decay rate Γ = 0.3(1)M Hz, which is in good agreement with measurements of Γ [14] made independently of the present experiment. Additionally measurements of ∆S 12 (τ ) at 8MHz Raman detuning show, that outside the EIT regime there is no correlation effect at all!…”

Phase control of electromagnetically induced transparency in a double-Λ system

“…The phase-dependent nature of EIT in such excitation systems has applications in e cient frequency conversion [27], use of theoretically predicted phase matching [26] for laser phase locking or amplitude and phase¯uctuation correlation, selective photoexcitation of molecules [28], or development of novel e cient optoelectronic devices like coherent switches, amplitude, phase and frequency modulators, wavelength converters, etc.…”

Probing degenerate two-level atomic media by coherent optical heterodyning

“…In a strongly driven two-level atomic system, FWM can be enhanced by the ac-Stark effect as shown in [9,10], while in an alkali atomic vapour, it can be further enhanced in the vicinity of a Raman transition. Previous studies have demonstrated that light-induced coherence between groundstate sublevels, which is responsible for the effects of coherent population trapping (CPT) [11] and electromagnetically induced transparency (EIT) [12], may facilitate the generation of new optical components detuned from the applied radiation by the ground-state splitting [13][14][15]. It was shown that light propagation in EIT atomic media with a double-level configuration is affected by resonant FWM [16].…”