Storage and retrieval of parametric down-conversion (PDC) photons are demonstrated with electromagnetically induced transparency (EIT). Extreme frequency filtering is performed for THz order of broadband PDC light and the frequency bandwidth of the light is reduced to MHz order. Storage and retrieval procedures are carried out for the frequency filtered PDC photons. Since the filtered bandwidth [full width at half-maximum (FWHM) = 9 MHz] is within the EIT window (FWHM = 12.6 MHz), the flux of the PDC light is successfully stored and retrieved. The nonclassicality of the retrieved light is confirmed by using photon counting method, where the classical inequality which is only satisfied for classical light fields is introduced. Since the PDC photons can be utilized for producing the single photon state conditionally, storage and retrieval procedures are also performed for the conditional single photons. Anti-correlation parameter used for checking the property of single photon state shows the value less than 1, which means the retrieved light is in a non-classical region.

The broadband parametric fluorescence pulse (probe light) with center frequency resonant on 87 Rb D1 line was injected into a cold atomic ensemble with coherent light (control light). Due to the low gain in the parametric down conversion process, the probe light was in a highly bunched photon-pair state. By switching off the control light, the probe light within the electromagnetically induced transparency window was mapped on the atoms. When the control light was switched on, the probe light was retrieved and frequency filtered storage was confirmed from the superbunching effect and an increase of the coherence time of the retrieved light.

High-current Cu ion beams were extracted from a laser-produced plasma using a pulsed high-voltage multiaperture diode driven by an induction cavity. The amplitude and the duration of the extraction voltage were 130 kV and 450 ns, respectively. During the extraction, explosive beam divergence due to the strong space-charge force was suppressed by the focusing action of the gap between concentric hemispheres. Modulation of the extracted beam flux due to the plasma prefill in the gap has been eliminated by using a biased control grid put on the anode holes. By means of this extraction scheme we obtained a rectangular beam pulse with a rise time as short as 100 ns. The beam current behind the cathode was limited to 0:1 A, owing to space-charge effects, as well as to poor geometrical transmission through the cathode sphere. From the measurement of the extracted beam current density distribution along the beam axis and the beam profile measurement, we found a beam waist slightly downstream of the spherical center of the diode structure. The measured beam behavior was consistent with numerical results obtained via a 3D particle code. No serious degradation of the beam emittance was observed for the grid-controlled extraction scheme.

There is presently much interest in tunable, flexible, or reconfigurable metamaterial structures that work in the terahertz frequency range. They can be useful for a range of applications, including spectroscopy, sensing, imaging, and communications. Various methods based on microelectromechanical systems have been used for fabricating terahertz metamaterials, but they typically require high-cost facilities and involve a number of time-consuming and intricate processes. Here, we demonstrate a simple, robust, and cost-effective method for fabricating flexible and stackable multiresonant terahertz metamaterials, using silver nanoparticle inkjet printing. Using this method, we designed and fabricated two arrays of split-ring resonators (SRRs) having different resonant frequencies on separate sheets of paper and then combined the two arrays by stacking. Through terahertz time-domain spectroscopy, we observed resonances at the frequencies expected for the individual SRR arrays as well as at a new frequency due to coupling between the two SRR arrays.

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