Peiying Li

Observation of dressed odd-order multi-wave mixing in five-level atomic medium

By selectively blocking specific laser beams, we investigate coexisting seven distinguishable dressed odd-order multi-wave mixing (MWM) signals in a K-type five-level atomic system. We demonstrate that the enhancement and suppression of dressed four-wave mixing (FWM) signal can be directly detected by scanning the dressing field instead of the probe field. We also study the temporal and spatial interference between two FWM signals. Surprisingly, the pure-suppression of six-wave mixing signal has been shifted far away from resonance by atomic velocity component. Moreover, the interactions among six MWM signals have been studied.

Controllable Multiwave Mixing Talbot Effect

We theoretically study the Talbot effects resulted from the four-wave mixing and six-wave mixing signals, which are periodically modulated due to the coherence control effect. Corresponding to different dressing states, the enhancement and suppression conditions that will affect the properties of the multiwave mixing signals are also discussed in detail. Such proposal can be useful in all-optical-controlled pattern formation and propagation of light.

Phase control of bright and dark states in four-wave mixing and fluorescence channels

We first investigate the phase control of the switch between bright and dark states in the transmitted probe, four-wave mixing (FWM) and fluorescence signals in a four-level  85Rb atomic system. With the relative phase modulated from 0 to −π, pure dark state in the FWM and fluorescence channels can be switched to pure bright state, corresponding to the switch from electromagnetically induced transparency to electromagnetically induced absorption. Meanwhile, the results could be obtained in solid crystals. Such phase controlled switch could have potential applications in optical communication and quantum information processing.

Observation of Autler-Townes splitting in six-wave mixing

We report an observation of the self- and external-dressed Autler-Townes (AT) splitting in six-wave mixing (SWM) within an electromagnetically induce transparency window, which demonstrates the interaction between two coexisting SWM processes. The multi-dressed states induced by the nested interactions between many dressing fields and the five-level atomic system lead to the primary, secondary and triple AT splittings in the experiment. Such controlled multi-channel splitting of nonlinear optical signals can be used in a range of applications, e.g. the wavelength-demultiplexer in optical communication and quantum information processing.

Switching suppression and enhancement of fluorescence and six-wave mixing by phase modulation

The conversion between enhancement and suppression in six-wave mixing (SWM) and fluorescence signals by phase modulation has demonstrated for the first time. It is observed in our experiment the suppression of SWM and fluorescence is transformed into enhancement in company with the switch from electromagnetically induced transparency (EIT) to electromagnetically induced absorption (EIA) in the transmitted probe with the relative phase changed from 0 to π/2. Our research could be potentially applied in optical communication and quantum information processing.

Optical cavity squeezing of multiwave mixing via dark states

We theoretically demonstrate the influence of dark states on single-mode and two-mode optical squeezing in a four-level atomic–cavity coupling system through fifth- and third-order cascade nonlinearity. We first show the cone emissions of self-diffraction and phase-conjugate spontaneous parametric (SP) four-wave mixing processes. Then, we inject a coherent or Einstein–Podolsky–Rosen field into the SP-MWM channels to investigate the corresponding squeezing. The investigations have potential applications in quantum information processing.

Controlling cascade dressing interaction of four-wave mixing image

We report our observations on enhancement and suppression of spatial four-wave mixing (FWM) images and the interplay of four coexisting FWM processes in a two-level atomic system associating with three-level atomic system as comparison. The phenomenon of spatial splitting of the FWM signal has been observed in both x and y directions. Such FWM spatial splitting is induced by the enhanced cross-Kerr nonlinearity due to atomic coherence. The intensity of the spatial FWM signal can be controlled by an additional dressing field. Studies on such controllable beam splitting can be very useful in understanding spatial soliton formation and interactions, and in applications of spatial signal processing.

Comparison of Two Two-Photon Dressed Rules in Multi-Wave Mixing

For the first time, we report a novel two-photon dressed rule in a five-level 85Rb atomic system. In comparison with a traditional two-photon dressed rule where the signals move with probe field frequency detuning changing, the novel one indicates that the signals do not move with coupling field frequency detuning changing. The finding is verified by the experimentally detected transmitted probe, multi-wave mixing, and fluorescence signals. We also find that the fluorescence signals show Autler-Townes splitting, which are observed experimentally and explained theoretically. By scanning one coupling field frequency detuning, variation of the dressing strength of another coupling field is revealed. Finally, we demonstrate that the alternation can be phase controlled if one of the incident beams deviates an angle (i.e., change from a normal state to an abnormal state).

Observation of angle-modulated switch between enhancement and suppression of nonlinear optical processes

We simultaneously investigate the four-wave mixing and the fluorescence signals via two cascade electromagnetically induced transparency (EIT) systems in atomic rubidium vapor. By manipulating the deflection angle between the probe beam and certain coupling beams, the dark state can extraordinarily switch to bright state, induced by the angle-modulation on the dressing effect. Besides, in the fluorescence signal, the peak of two-photon fluorescence due to classical emission and the dip of single-photon fluorescence due to dressing effect are distinguished, both in separate spectral curves and in the global profile of spectrum. Meanwhile, we observe and analyze the similarities and discrepancies between the two ground-state hyperfine levels F = 2 and F = 3 of Rb 85 for the first time.

Polarized Suppression and Enhancement of Six-Wave Mixing in Electromagnetically Induced Transparency Window

We show that polarization properties of the suppression and enhancement as well as the Autler-Townes (AT) splitting of two coexisting six-wave mixing (SWM) processes in multi-Zeeman levels atomic system. By scanning the frequency detuning of the dressing field, we observe the suppression and enhancement as well as the AT splitting of the two coexisting SWM processes with the different polarized probe beams. Different polarization states of the probe beam can select different transitions among multi-Zeeman levels and different dressing strengths. The AT splitting separations get slightly large as the probe beam changes from the linearly polarized state to the circularly polarized one. Under the conditions of different dressing fields, the polarization dependence of the SWM enhancement and suppression shows the inverse variation. Theoretical calculations are carried out, which are in good agreement with the experimental results.