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Abstract: In our experiment, two channels of a 3cm long periodically poled lithium niobate (PPLN) waveguide are used to generate the nondegenerate spontaneous parametric down conversion (NSPDC) photon pairs. We experimentally obtained the highly efficient polarization-entangled photon pairs by coherently combining two NSPDC processes, and keeping the phase stable over 30min. We can also prepare two entangled photon pairs with different central wavelengths with the help of wavelength division multiplex. [Copyright &y& Elsevier]

We propose a scheme for the direct measurement of the Wigner function of a cavity field with no more than three photons around the origin. In the scheme the cavity field is first displaced by a small amount. Then a two-level atom is sent through the cavity. After a resonant interaction time the difference between the probabilities of the atom being in the ground and excited states is directly related to the Wigner function for the field state. The scheme can also be used for conditional generation of four-photon and six-photon states using two and three resonant atoms, respectively. [Copyright &y& Elsevier]

Abstract: We report the experimental observation of the effect of spontaneously generated coherence on absorption without the rigorous requirement of close-lying levels. The experiments are studied in both a four-level N-type and a four-level inverted-Y-type atomic system in a rubidium atomic beam. With the coupling and controlling field, the N-type system is equivalent to a system with three closely upper levels coupled to one lower level by the same vacuum modes. The quantum interference can induce two prominent and nearly transparent holes where the slope of the refractive index is very steep. This special situation could allow the simultaneous propagation of two weak pulses with different frequencies. When we tune the wavelength of the controlling field, the N-type system turns to be the inverted-Y atomic system. Under the two-photon resonance condition, the system is equivalent to a V-type system with two closely upper levels, and the interference can reduce one broad transparency window in the middle of the absorption spectrum. Besides we can control the number of the spontaneously decay channels by the detuning of the controlling field, thus the effect of spontaneously generated coherence can exist in three or two closely space levels. [Copyright &y& Elsevier]

Abstract: In an N-type atomic system with double electromagnetically induced transparency, when the traveling-wave coupling field is replaced by a standing-wave, double fully developed photonic band gaps open up due to space-modulated refractive index within the two electromagnetically induced transparency widows. The dynamically induced band gaps can be tuned coherently, and have applications in manipulating the propagation dynamics of light pulses. [Copyright &y& Elsevier]

Abstract: We report a systematic study of AgGaS2- and Al-doped GaSe crystals in comparison with pure GaSe and S-doped GaSe crystals. AgGaS2-doped GaSe (GaSe:AgGaS2) crystal was grown by Bridgman technique from the melt of GaSe:AgGaS2 (10.6wt.%). Its real composition was identified as GaSe:S (2wt.%). Al-doped GaSe (GaSe:Al) crystals were grown from the melt of GaSe and 0.01, 0.05, 0.1, 0.5, 1, 2 mass% of aluminium. Al content in the grown crystals is too small to be measured. The hardness of GaSe:S (2wt.%) crystal grown from the melt of GaSe:AgGaS2 is 25% higher than that of GaSe:S (2wt.%) crystal grown by a conventional S-doping technique and 1.5- to 1.9-times higher than that of pure GaSe. GaSe:Al crystals are characterized by 2.5- to 3-times higher hardness than that of pure GaSe and by extremely low conductivity of ≤10−7 Om−1 cm−1. A comparative experiment on SHG in AgGaS2-, Al-, S-doped GaSe and pure GaSe is carried out under the pumps of 2.12–2.9μm fs OPA and 9.2−10.8μm ns CO2 laser. It was found that GaSe:S crystals possess the best physical properties for mid-IR applications among these doped GaSe crystals. GaSe:Al crystals have relatively low conductivity which have strong potential for THz application. [Copyright &y& Elsevier]

Abstract: A scheme for two-dimensional (2D) subwavelength atom localization is proposed, in which the atom is in an inverted-Y configuration and driven by two orthogonal standing-wave lasers. Due to the spatial dependence of atom–field interaction, the quantities of system, including the frequency of spontaneously emitted photon, the population in the excited state, and the probe absorption, carry information about the position of atom in standing-wave fields. We exploit this fact to 2D atom localization, and obtain a high precision and resolution in the position probability distribution. [ABSTRACT FROM AUTHOR]

Abstract: Nanosecond time-resolved evolution of coherence between two nondegenerate ground levels has been investigated in Rb atomic vapor. Using STIRAP and fractional STIRAP, a time-dependent coherence is prepared and indirectly monitored by the generated coherent Raman scattering signal proportional to the coherence. The experimental data fit very well with numerical simulations. This technique have potential applications in nonlinear process based on atomic coherence. [Copyright &y& Elsevier]

Abstract: In this report, we demonstrate the efficient generation of collinearly propagating photon pairs in a bulk periodically poled potassium titanyl phosphate pumped by a cw laser. The detected coincidence counts are more than 7400/s with 3.58mW pump power in a Hanbury–Brown–Twiss-type experiment. The estimated photon pair production rate is about 0.73MHz/mW. This is very promising for some applications, such as quantum key distribution, proof of the Bell-inequality, preparation of single photon states in broadband wave packets, Franson-type interference and so on. [Copyright &y& Elsevier]