Huayan Lan

All-optically controlled fourth- and sixth-order fluorescence processes of Pr3+:YSO

We report all-optically controlled fourth- and sixth-order fluorescence processes with and without splitting, in a heteronuclear-like molecule system of Pr3+:YSO both in theory and experiment. We construct the asymptote among Pr3+ ions localized at different cation vacancies. By changing the frequency detuning and power of the controlling field, fluorescence signal can be controlled to switch from an enhanced peak to a suppressed dip, and vice versa. Such transition has a potential application to produce all-optical switches. The results can be well explained by a theory model based on the high-order coherent process.

Competition between spontaneous parametric four-wave mixing and fluorescence in Pr3+:YSO

We report the competition between the spontaneous parametric four-wave mixing and second- or fourth-order fluorescence (FL) signals in Pr3+:Y2SiO5 crystal. By changing the powers of controlling fields and blocking different fields, the competitive two signals can be identified through the dressing effect. Meanwhile, the delay of fourth-order FL in the time domain results from splitting the energy level. Such results can find potential applications in optical information storage and processing on a photonic chip.

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.

Suppression and enhancement of coexisting super-fluorescence and multi-wave mixing processes in sodium vapor

Different aspects of the properties of the coexisting super-fluorescence (SFL), multi-wave mixing with the fluorescence signal in the sodium vapor are studied both theoretically and experimentally. First, by scanning the dressed-state, the properties of these coexisting processes, such as the SFL signal modulated by using the dark and bright states, the interplay between dressed-states, are observed for the first time. Then, by scanning the probe field, the interplay between the one-photon and two-photon processes of the coexisting signals is obtained with or without the external dressing fields. Such control on each process in such coexisting system has an important potential application in quantum communication.

Seeded spontaneous parametric four-wave mixing and fluorescence of Pr3+:YSO

We demonstrate the seeded spontaneous parametric four-wave mixing (SP-FWM) process associated with the fluorescence signals of Pr 3+ :YSO both theoretically and experimentally. For the first time, the dressed SP-FWM processes are observed by self-dressing and/or external-dressing in this crystal. Various possible amplification processes are discussed by selectively seeding various multi-wave mixing (MWM) signals. Two contributions of the dressing effect and the dipole–dipole interaction to the linewidths of the SP-FWM signal and the conjugate signal of the seeding MWM signal associated with the fluorescence signal have been distinguished. In addition, the Autler–Townes-like (or Autler–Townes) splitting effect of the fluorescence spectrum induced by itself (or external) field and the mutual interaction between two fluorescence signals are investigated which are well explained using the presented theoretical model. Such results can find potential applications in all-optical communication and optical information processing on a photonic chip.

Observation of Angle Switching of Dressed Four-Wave Mixing Image

We experimentally report that angle-control dynamics in the nonlinear propagation of the images of the probe, generated four-wave mixing (FWM) and fluorescence signals beams in FWM process in a cascade three-level, as well as a two-level atomic systems. It is shown that, by changing the angles between pumping fields and dressing fields, respectively, the characteristics of the measured signals including the spectra intensity and spatial images can be controlled to display many effects, including the electromagnetically induced transparency and absorption (EIT and EIA, respectively) and Autler-Townes splitting. In particular, we demonstrate the angle-controlled switching from EIA to EIT in probe transmission or from enhancement to suppression in FWM signal. Additionally, we also illustrate the interaction between spatial characteristics and spectra intensities of weak fields. The studies can be very useful in producing all optical-signal-processing devices, such as spatial beam splitters, routers, and switches.

Multidressed suppression and enhancement of spontaneous parametric four-wave-mixing processes

For the first time to our knowledge, a dressed spontaneous parametric four-wave mixing (SP-FWM) process and fluorescence (FL) signals in hot alkali atom vapor are demonstrated in both theory and experiment. First, by scanning pumping fields, Autler–Townes (AT) splitting in SP-FWM and two-photon suppression dip in FL are observed. Then, by scanning coupling fields, single-, double-, and triple-dressed effect on those signals is demonstrated, such as suppression and/or enhancement of SP-FWM signal and suppressed two-photon emission peak of FL. The interaction effect between dressing fields on SP-FWM and FL signals is also observed. Such investigations can find potential applications in multichannel narrowband long-distance communication.

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.

Noise correlations controlled by dressed suppression and enhancement

The intensity noise correlations between anti-Stokes and Stokes fields, generated from spontaneous parametric four-wave mixing (SP-FWM) process have been investigated in a ladder-type three-level system of sodium atomic vapor. By introduction of an external dressing field, the strengthened (weakened) correlations are obtained under enhancement (suppression) condition of SP-FWM. Besides, sharp correlations have been obtained as attributed to a pair of non-classical beams generated from amplified spontaneous emission.