Terahertz (THz) sources, ranging from 0.1 THz to 10 THz, between microwaves and infrared waves, have important applications in spectral detection, medical imaging, communication, etc. Difference frequency generation (DFG) is an effective method for generating terahertz with the characteristics of low cost, simple structure, widely tunable range, no threshold, room-temperature operation. This pa...

The Columbia University Microbeam II has been built to provide a focused ion beam for irradiating designated mammalian cells with single particles. With the interest in irradiating non-stained cells and cells in three-dimensional tissue samples, the endstation was designed to accommodate a variety of imaging techniques, in addition to fluorescent microscopy. Non-stained cells are imaged either ...

Highly phase-mismatched nonlinear interactions can generate spatially localized optical fields that can affect the performance of nonlinear optical devices. We present a theoretical description of the generation of such spatially localized optical fields by ultrafast pulses. The effects of temporal walk-off and pump depletion are discussed, along with methods for suppression of the localized fi...

Efficient generation of coherent blue light is of immediate importance for the development of numerous applications in areas such as displays, optical data storage and printing, and nonlinear frequency conversion achieved by quasiphase-matched ~QPM! interaction remains an attractive route for realizing such devices. QPM requires precise control of periodic domain inversion, with periods that ca...

Stoichiometric lithium tantalate (SLT) has been identified as a promising alternative to congruent lithium niobate as substrate material for quasi-phasematched (QPM) nonlinear optical frequency conversion. The advantages of SLT include superior resistance to optical damage, greater ultraviolet transparency, and a lower coercive field which should facilitate the fabrication of thicker periodical...

We have applied the fast timing βγγ(t) technique to remeasure lifetimes of selected states in Ra populated in the β− decay of Fr. T1/2 = 587(12) ps and 210(13) ps have been obtained for the 3/2− and 5/2− states at 50.1 and 79.7 keV, that are more accurate than the previous values of 630(70) ps and 166(55) ps, respectively. Our |D0| value of 0.155(10) e·fm obtained for the K = 3/2 configuration ...

Abstract. Low-energy dipole excitations have been investigated theoretically in N=50 Sr and Zr, several N=82 isotones and the Z = 50 Sn isotopes. For this purpose a method incorporating both HFB and multi-phonon QPM theory is applied. A concentration of one-phonon dipole strength located below the neutron emission threshold has been calculated in these nuclei. The analysis of the corresponding ...

This paper presents a novel method, Navigation-Pattern-based Relevance Feedback (NPRF), to achieve the high efficiency and effectiveness of CBIR in coping with the large-scale image data. In terms of efficiency, the iterations of feedback are reduced substantially by using the navigation patterns discovered from the user query log. In terms of effectiveness, our proposed search algorithm NPRF S...