Storage of Airy wavepackets based on electromagnetically induced transparency.

The research of Airy beams has attained much attention due to their unique characteristics. Coherent control of Airy beams is important for further light beam manipulation and information processing. In this paper, we experimentally investigate the storage and retrieval of 2D Airy wavepackets in a solid-state medium driven by electromagnetically induced transparency (EIT). The transverse profile of the weak probe pulse is modulated by Airy wavepackets. Under EIT condition, the probe Airy wavepackets are stored into the experimental medium by manipulating the intensity of the control field, and later retrieved by the opposite process. The retrieved Airy wavepackets keep a high similarity compared with those before the storage. Furthermore, the self-healing property of the retrieved Airy wavepackets is investigated. This storage of Airy wavepackets develops the control method of Airy beams, which will be useful in further applications.

Blocking the interaction between circTNRC18 and LIN28A promotes trophoblast epithelial-mesenchymal transformation and alleviates preeclampsia.

Defects in migration and invasion caused by dysregulation of trophoblastic epithelial-mesenchymal transformation (EMT) play a vital role in preeclampsia (PE). We have previously shown that circTNRC18 inhibits the migration and EMT of trophoblasts; however, its role in PE remains unknown. Herein, we demonstrate that circTNRC18 interacts with an RNA-binding protein, lin-28 homolog A (LIN28A), and this interaction is enhanced in PE placental tissue. LIN28A overexpression suppresses circTNRC18-mediated inhibition of trophoblast migration, invasion, and EMT, whereas LIN28A knockdown promotes them. The intracellular distribution of LIN28A is regulated by circTNRC18, where it promotes the expression of insulin-like growth factor II by stabilizing its mRNA. circTNRC18 also promotes complex formation between GATA-binding factor 1 (GATA1) and sine oculis homeobox 1 (SIX1) by inhibiting LIN28A-GATA1 interaction. GATA1-SIX1 promotes transcription of grainyhead-like protein 2 homolog and circTNRC18-mediated regulation of cell migration and invasion. Moreover, blocking circTNRC18-LIN28A interaction with antisense nucleotides alleviates PE in a mouse model of reduced uterine perfusion pressure. Thus, targeting the circTNRC18-LIN28A regulatory axis may be a novel PE treatment method.

Control of spontaneous emission from a micro-wave driven atomic system.

We demonstrate coherent control of spontaneous emission from an indirectly coupled transition in a microwave driven four-level atomic system. The transition of concern is not directly coupled by any laser fields, while the ground state is coupled to another ground state by a microwave field. We show that the coupling of the microwave field produces interesting features such as double narrow lines in the emission spectrum. The heights, widths and positions of the emission peaks can be controlled by modifying the Rabi frequency and detuning of the microwave field. We discuss the spectra in the dressed states basis.

Observation of the fluorescence spectrum for a driven cascade model system in atomic beam.

We experimentally study the resonance fluorescence from an excited two-level atom when the atomic upper level is coupled by a nonresonant field to a higher-lying state in a rubidium atomic beam. The heights, widths and positions of the fluorescence peaks can be controlled by modifying the detuning of the auxiliary field. We explain the observed spectrum with the transition properties of the dressed states generated by the coupling of the two laser fields. We also attribute the line narrowing to the effects of Spontaneously Generated Coherence between the close-lying levels in the dressed state picture generated by the auxiliary field. And the corresponding spectrum can be viewed as the evidence of Spontaneously Generated Coherence. The experimental results agree well with calculations based on the density-matrix equations.

Efficient frequency conversion induced by quantum constructive interference.

We demonstrate in experiment an efficient cw four-wave mixing scheme with maximal intensity conversion efficiency up to 73% in a double-Λ system of hot rubidium atoms. Relevant theoretical analysis shows that this high conversion efficiency benefits greatly from the constructive interference between two four-wave mixing channels, characterized by two different space-dependent phases.

Dual-channel all-optical wavelength conversion switching by four-wave mixing.

We report an experimental demonstration of dual-channel all-optical wavelength conversion switching in hot Rb vapor. In a four-level atomic system, a coupling field and a pump field interact with both (87)Rb and (85)Rb isotopes simultaneously and facilitate the generation of two nonlinear signals when the probe field is applied to the corresponding transition. Each nonlinear signal is switched on and off separately by the pump field at different frequencies based on four-wave mixing and isotope shifts.

Three-channel all-optical routing in a Pr3+:Y2SiO5 crystal.

We experimentally demonstrate a three-channel all-optical routing based on light storage in a Pr(3+):Y(2)SiO(5) crystal. By switching off the control field under the condition of electromagnetically induced transparency, the optical information of the probe light pulse can be stored in the crystal. When three retrieve control fields are switched on in the release process, the stored optical information from one light channel can be transferred (or distributed) into three different light channels. Also we show that this all-optical routing can be time-delayed. Such a multichannel all-optical routing in solids may have practical applications in quantum information and all-optical network.

Slowing and storage of double light pulses in a Pr3+:Y2SiO5 crystal.

We experimentally demonstrate the slowing and storage of double light pulses in a Pr(3+):Y(2)SiO(5) crystal using a multilevel-tripod scheme. Owing to double dark-state polaritons of the tripod-type system, two signal pulses can be simultaneously slowed. Also, we realize the simultaneous storage (and retrieval) of double light pulses by switching off (and back on) the control field. Slowing and storage of double light pulses in solids may have practical applications in quantum information and quantum networks.

SHG in doped GaSe:In crystals.

Optical transmission range and phase matching (PM) conditions for second harmonic generation (SHG) of Er3+:YSGG and CO2 laser in indium doped GaSe:In(0.1, 1.23, 2.32 mass%) are studied in comparison with these in pure and sulfur doped GaSe:S(0.09, 0.5, 2.2, 3 mass%) crystals. No changes in transparency curve are found in GaSe crystals up to 2.32 mass% indium content, but as small change as 0.18 degrees in PM angle for 2.79 microm Er3+:YSGG laser SHG and approximately 0.06 degrees for 9.58 microm CO2 laser emission line SHG are detected. PM properties of the crystals are evaluated as a function of temperature over the range from -165 to 230 degrees C. The value of dtheta/dT, the change in PM angle with variation of temperature, is found to be very small for GaSe:In crystals. While for SHG of Er3+:YSGG laser, dtheta/dT =22"/1 degrees C only, it is as small as -4.9"/1 degrees C for that of CO2 laser radiation. Linear variation of PM angle with temperature increasing is an indicator of absence of crystals structure transformation within temperature range from -165 to 230 degrees C. Thus, application of GaSe:In solid solutions in high average power nonlinear optical systems seems to be prospective.

SHG phase matching in GaSe and mixed GaSe1(1-x)S(x), x < or =0.412, crystals at room temperature.

The optical properties of p-type GaSe and mixed GaSe(1-x)S(x), x=0.04, 0.023, 0.090, 0.133, 0.175, 0.216, 0.256, 0.362, 0.369, and 0.412, crystals were studied to reveal the potentials for phase matching and frequency conversion. Comparative experiment on Er3+:YSGG and CO2 laser SHG at identical experimental conditions is carried out at room temperature. Any change in polytype structure of GaSe1(1-x)S(x) was not found.

Construction of refractive-index profile of Ag+-Na+ ion-exchange channel waveguide by two-dimensional inverse matrix method.

The refractive-index profile of ion-exchange channel waveguide is reconstructed by near-field measurement combined with two-dimensional inverse matrix method, which can avoid the problems brought by multimeasurements and iteration smoothing in the process. The method used here has the advantages of convenient operation and accurate results for the characteristics of the asymmetric channel waveguide. It can be also applied to the refractive-index profile measurements of graded index fibers, polarization maintaining fibers, and single-mode planar waveguides.

[Infrared spectral studies of separation of QAPVA/PMPVA complex membrane for dehydrating water of 95% ethanol].

Quaternized polyvinyl alcohol (QAPVA) and phosphate monoester polyvinyl alcohol (PMPVA) were self-assembled into polyion complex (PIC) membrane. The infrared spectra (IR) of PIC membrane dipped in 95% ethanol for 48 h were studied in the temperature range of 20-120 degrees C with an interval of 20 degrees C by analyzing the temperature dependent variations of OH stretch vibration base bands (upsilonOH) at >3000 cm(-1). Hydrogen-bond of water in 95% ethanol with PIC was studied. Since the upsilonOH strongly overlapped at >3000 cm(-1), combined with the static electric effect between water in 95% ethanol and ion-bond of PIC at 1300-1700 cm(-1), two-dimensional infrared (2DIR) correlation analysis was applied to describe the possible combined modes between PIC and water in water-alcohol. The result shows that the upsilonOH overlapped was distinguished at >3000 cm(-1), the change of water with varing tempertature was earlier than the intra-membrane OH self association and water was desorbed to separate from ethanol. The absorption peak of water and poly-electrolyte group intra-PIC membrane was identified. The water combined with ion-bond in PIC membrane by static electric effect was adsorbed with the temperature going up and separate from ethanol. The present study provides a simple method for investigating the separation performance of PIC membrane used in dehydration of organic compounds.

Observation of CARS signal via maximal atomic coherence prepared by F-STIRAP in a three-level atomic system.

We control the atomic coherence and the population transfer among Rb hyperfine atomic levels by the fractional stimulated Raman adiabatic passage (F-STIRAP) in a L-type configuration, and verify the theoretical predictions. Applying this technique, we are able to prepare the atoms with maximal coherence to enhance coherent anti-Stokes Raman scattering (CARS) signal. In our experiment by scanning the frequency of one laser from 794.9839 nm to 794.9844 nm with the 794.9698 nm laser frequency fixed to generate a maximum of the CARS signal we are able to obtain the energy level diagram of the sample.

Optical information transfer between two light channels in a Pr(3+):Y(2)SiO(5)crystal.

We experimentally demonstrate light storage and release in a four-level double-lambda atomic system of a Pr (3+):Y(2)SiO(5) crystal. Based on the technique of light storage, we realize optical information transfer between two light channels. The coherent optical information of a probe pulse stored in the crystal can be selectively released into two different light channels by varying the frequency and propagation direction of the switch-on control field.

Wide-tunable, high-energy AgGaS(2) optical parametric oscillator.

Nanosecond AgGaS(2) type-I singly resonant optical parametric oscillator pumped by a Q-switched 1.064 mum Nd:YAG laser is demonstrated experimentally. Continuously tunable 2.6-5.3 mum radiation and output pulse energy up to 0.6 mJ at 4 mum are achieved in a single-stage conversion process. The analysis of pump threshold is investigated both theoretically and experimentally.

Image routing via atomic spin coherence.

Coherent storage of optical image in a coherently-driven medium is a promising method with possible applications in many fields. In this work, we experimentally report a controllable spatial-frequency routing of image via atomic spin coherence in a solid-state medium driven by electromagnetically induced transparency (EIT). Under the EIT-based light-storage regime, a transverse spatial image carried by the probe field is stored into atomic spin coherence. By manipulating the frequency and spatial propagation direction of the read control field, the stored image is transferred into a new spatial-frequency channel. When two read control fields are used to retrieve the stored information, the image information is converted into a superposition of two spatial-frequency modes. Through this technique, the image is manipulated coherently and all-optically in a controlled fashion.

Investigation on "Excimer" Formation Mechanism of Linear Oligofluorenes-Functionalized Anthracenes by Using Transient Absorption Spectroscopy.

We study the photophysical characters of two oligofluorenes-functionalized anthracenes molecules with different fluorine-vinylene (FV) units, which exhibits that "excimer" state appears in the solution after photoexcitation. The dynamic data shows that two mechanisms are responsible for the generation of "excimer". The fast one is controlled by the arene-arene interaction between molecules and the slow one is influenced by the diffusion motion of molecules. Increasing the number of FV units may suppress the DM-dependent "excimer" and enhance the yield of intrinsic fluorescence, which finally improves the fluorescence property of molecules in solution.

Investigation on Photophysical Properties of D-π-A-π-D-Type Fluorenone-Based Linear Conjugated Oligomers by Using Femtosecond Transient Absorption Spectroscopy.

The effects of π-spacer and electron donor groups on the photophysical behaviors of fluorenone-based linear conjugated oligomers have been systemically investigated. Solvent-dependent steady-state measurements exhibit that the fluorene vinylene (FV) spacer and the electron-donating ability of donor group are able to modulate the spectral features of oligomers and the fluorescence quantum yield could decrease with the increasing of the solvent polarity. Meanwhile, quantum chemical calculation simulates their absorption spectra, and analyzes their electron transition components simultaneously. The transient absorption measurements focus on the photoexcitation dynamics of these oligomers in the toluene solution, which show that an intramolecular charge transfer state exists in the relaxation process of excited states, and its generation process could accelerate with the introduction of FV spacer and the enhancement of donor strength.

Investigation of spontaneously generated coherence in dressed states of (85)Rb atoms.

We investigate the effects of spontaneously generated coherence (SGC) on the electromagnetically induced transparency features in a four-level Lambda-type system. We show that double-transparency windows and a controllable narrow absorption peak can be obtained with the presence of SGC. We present an equivalent system without the rigorous requirement of close-lying levels to observe the phenomena. We also experimentally demonstrate the corresponding features in a rubidium atomic beam.

Coherence transfer between atomic ground states by the technique of stimulated Raman adiabatic passage.

We experimentally and theoretically demonstrate that the atomic coherence can be completely transferred or arbitrarily contributed among the different levels in a four-level atomic (tripod) scheme by a group of coupled pulse sequences. This technique can be applied to the information conversion in slow-light storage, quantum logical gates, and so on, which is based on the atomic coherence effect.