Beams of ``squeezed'' light have important applications in quantum metrology and gravitational-wave detection. The authors generate twin beams of correlated photons using parametrically amplified four- and six-wave mixing in a nonlinear optical crystal. This medium offers several advantages, such as better on-chip integration than atomic vapors, plus a longer coherence time than traditional optical materials. These achievements can also find potential application in all-optical communication and quantum storage of light in photonic circuits.

Controlled Correlation and Squeezing in Pr 3 + : Y 2 SiO 5 to Yield Correlated Light Beams

We study the enhancement and suppression of different multi-waving mixing (MWM) processes in a Rydberg-EIT rubidium vapor system both theoretically and experimentally. The nonlinear dispersion property of hot rubidium atoms is modulated by the Rydberg-Rydberg interaction, which can result in a nonlinear phase shift of the relative phase between dark and bright states. Such Rydberg-induced nonlinear phase shift can be quantitatively estimated by the lineshape asymmetry in the enhancedand suppressed MWM processes, which can also demonstrate the cooperative atom-light interaction caused by Rydberg blockaded regime. Current study on phase shift is applicable to phase-sensitive detection and the study of strong Rydberg-Rydberg interaction.

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Phase Modulation in Rydberg Dressed Multi-Wave Mixing processes.

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.

http://iopscience.iop.org/article/10.1088/1612-2011/12/1/015404/pdf

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

We study the realization of an optical transistor (switch and amplifier) and router in multi-order fluorescence (FL) and spontaneous parametric four-wave mixing (SP-FWM). We estimate that the switching speed is about 15 ns. The router action results from the Autler-Townes splitting in spectral or time domain. The switch and amplifier are realized by dressing suppression and enhancement in FL and SP-FWM. The optical transistor and router can be controlled by multi-parameters (i.e., power, detuning, or polarization).

Ultrafast optical transistor and router of multi-order fluorescence and spontaneous parametric four-wave mixing in Pr 3+ :YSO

In a numerical investigation, we demonstrate the existence and curious evolution of vortices in a ladder-type three-level nonlinear atomic vapor with linear, cubic, and quintic susceptibilities considered simultaneously with the dressing effect. We find that the number of beads and topological charge of the incident beam, as well as its size, greatly affect the formation and evolution of vortices. To determine the number of induced vortices and the corresponding rotation direction, we give common rules associated with the initial conditions coming from various incident beams.

Optical vortices induced in nonlinear multilevel atomic vapors

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.

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

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.

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

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.

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

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.

Huayan Lan

Papers

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

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

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

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

Observation of Angle Switching of Dressed Four-Wave Mixing Image