Controlling the transition of bright and dark states via scanning dressing field

Cavity linewidth narrowing via double-dark resonances is experimentally observed using the Rb87 Zeeman splitting sublevels. With the steep dispersion led by the interacting dark resonances in the tripod-type electromagnetically induced transparency system, we narrow the cavity linewidth to 250 kHz at room temperature. Furthermore, the position of this ultranarrow cavity linewidth can be tuned in a 60 MHz coupling field detuning range.

Realization of cavity linewidth narrowing via interacting dark resonances in a tripod-type electromagnetically induced transparency system

Transmissivity of up to 200% has been observed in an absorption imaging study of electromagnetically induced transparency in cold sodium atoms, when a focused coupling beam is applied near the edge of the atom cloud. The signal behavior strongly depends on the frequency difference between the probe beam and the coupling beam. Such high transmissivity can be attributed to the strong focusing effect of the probe beam, when it propagates in a medium with spatially inhomogeneous refractive index induced by the coupling beam. A detailed numerical analysis based upon the Maxwell propagation equations is presented.

27aWM-1 Absorption imaging of electromagnetically-induced transparency in cold sodium atoms

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

The Autler?Townes doublet and triplet spectroscopy are well known in the literature. Here, atomic systems for quartuplet, quintuplet emission spectroscopy and their linkages with the sodium atom are investigated for display of the corresponding spectra. We explore the involved fundamental processes of quantum interference in these systems by examining the Laplace transform of the corresponding state-vector subjected to steady coherent illumination in the rotating wave approximation and Weisskopf?Wigner treatment of spontaneous emission as a simplest probability loss. In the quartuplet (quintuplet), four (five) fields interact appropriately and resonantly with the five-level (six-level) atom. The spectral profile of the single decaying level, upon interaction with three (four) other levels, splits into four (five) destructively interfering dressed states generating three (four) dark lines in the spectrum. These dark lines divide the spectrum into four (five) spectral components (bright lines) whose widths are effectively controlled by the relative strength of the laser fields and the relative width of a single decaying level. The idea is also extended to higher-ordered spectroscopy. The apparent disadvantage of these schemes is the successive increase in the number of laser fields required for the strongly interactive atomic states. However, these complexities are naturally inherited and are the beauty of these atomic systems. They provide the foundations for the basic mechanisms of the quantum interference involved in the higher-ordered multiplet spectroscopy.

https://iopscience.iop.org/article/10.1088/1054-660X/24/3/035702/pdf

Autler-Townes multiplet spectroscopy

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.

Observation of Autler-Townes splitting in six-wave mixing.

We successfully observed the nonlinear eight-wave mixing (EWM) signal via one electromagnetically induced transparency (EIT) window and double optical pumping channels in an open five-level atomic system of 87Rb. By carefully controlling the arrangement of the incident laser beams, the corresponding four-wave mixing (FWM), six-wave mixing (SWM) and EWM signals can be made to coexist with similar signal amplitudes and transmit through the same EIT window in such open five-level atomic system.

https://iopscience.iop.org/article/10.1209/0295-5075/94/64005/pdf

Observation of eight-wave mixing via electromagnetically induced transparency

We experimentally observe the interplay among coexisting multiwave-mixing (MWM) signals via multiple electromagnetically induced transparency (EIT) windows, including two ladder-type EIT windows and one V-type EIT-like window in a five-level atomic system of Rb85. In the presence of these EIT windows, one can control the interplay between these MWM signals easily by changing the frequency detuning. Meanwhile, we also report the spatial and temporal interferences with a femtosecond time scale among three coexisting MWM signals in two overlapped EIT windows.

Interference of three multiwave mixings via electromagnetically induced transparency

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.

Ruyi Zhang

Papers

Observation of Autler-Townes splitting in six-wave mixing.

Observation of eight-wave mixing via electromagnetically induced transparency

Interference of three multiwave mixings via electromagnetically induced transparency

Controlling cascade dressing interaction of four-wave mixing image