Observation of transient electromagnetically induced transparency in a rubidium Λ system

Abstract

Observation of transient effects in electromagnetically induced transparency ͑EIT͒ is reported in Rb 85 cooled in a magneto-optical trap. The transmission of a weak probe beam in resonance with the 5S 1/2 (Fϭ3) to 5P 3/2 (Fϭ3) hyperfine transition increased transiently when a relatively strong coupling field in resonance with the 5S 1/2 (Fϭ2) to 5 P 3/2 (Fϭ3) hyperfine transition was switched on rapidly using a Pockels cell. The probe transient showed an initial Rabi half-cycle overshoot before settling down to steady-state EIT. The results agreed well with computations using a three-state model of the ⌳ system. The computations also suggest that transient gain should be observed with coupling field power only four times larger than that presently available to us. ͓S1050-2947͑98͒03308-3͔PACS number͑s͒: 42.50. Gy, 32.80.Pj, 42.50.Md The steady-state absorption of a weak resonant probe beam can be reduced or even eliminated by the presence of a strong coherent coupling beam exciting a linked transition. This effect, known as electromagnetically induced transparency ͑EIT͒, was first observed in 1991 ͓1,2͔. Related work on coherent population trapping in three-level systems dates from the mid-1970s and has been recently reviewed ͓3͔. In the last few years steady-state EIT has been widely studied in vapor cells and more recently in laser-cooled samples, see reviews ͓4,5͔. Transient EIT effects, however, have received relatively little explicit attention. In the first EIT experiments ͓1,2͔ the coupling field was provided by a high power pulsed laser with pulse rise and fall times that were slow compared with the Rabi period of the field. The transient approach to transparency in this adiabatic regime has been analyzed by Harris and Luo ͓6͔ from the point of view of energy requirements for the establishment of the transparency. We are interested in the nonadiabatic regime where the coupling field is switched on in a time that is short compared with Rabi periods and relaxation times. The only reported experimental study in this regime is that of Fry et al. ͓7͔, who observed transient absorption of a probe pulse in a ⌳ system immediately after the coupling beam was rapidly switched off. This is the converse of our experiment where the coupling field is rapidly switched on. Three-state models of transient effects in probe transmission when the coupling field is switched on nonadiabatically have been reported ͓8,9͔. In these models the transmission of a weak resonant probe approaches the steady-state EIT via damped oscillations characterized by the Rabi frequency of the relatively strong coupling field ⍀ C and the excited state decay rate ⌫, and for a sufficiently strong coupling beam there are intervals of probe gain without inversion, even without incoherent pumping. Thus there are possible applications to fast optical switching and lasing without inversion.We report an observation of transient EIT effects in the nonadiabatic regime, using a 85 Rb sample cooled in a magneto-optical trap ͑MOT͒. A three-level ⌳ system wa...

Transient properties of modified reservoir-induced transparency

“…This behaviour of the system is related to the one predicted [3] and experimentally observed [4] in a typical three level Λ-type atomic system which exhibits electromagnetically induced transparency through the application of a coupling laser field. The difference in our case, is that the transparency and the transient gain without inversion occur due to the coupling to a radiation reservoir with an inverse square-root singularity of the density of modes at threshold and are not induced by an external laser field.…”

Bichromatic electromagnetically induced transparency in cold rubidium atoms

“…This phenomenon is known as electromagnetically induced transparency (EIT) [1][2][3]. In recent years, many studies on EIT and related phenomena have been carried out, which reveal the importance of EIT in understanding the fundamental physics involving interactions between light field and resonant medium [4][5][6][7][8]. It has been shown that EIT may have applications in a variety of research topics such as quantum optics with slow photons [9][10][11][12][13], quantum information processing [14], atomic frequency standard [15][16][17][18], and quantum nonlinear optics [19,20].…”

Short-pulse cross-phase modulation in an electromagnetically-induced-transparency medium

“…There have been several multi-mode treatments of EIT, which examine the transients due to switching on optical fields [15,16] as well as of sudden changes in two-photon (Raman) resonance [17,18]. In addition, the transient properties of the associated nonlinearities, both absorptive (photon switching) [19,20] and dispersive (cross-Kerr effect) [21][22][23][24][25] have since been investigated.…”