SAMs Serve as Templates for Patterned Growth of Large Oriented Organic Semiconductor Single Crystals
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quantum teleportation applications. As reported in the October 1 issue of Optics Letters (p. 2635), Raphael C. Pooser and Olivier Pfister of the University of Virginia have demonstrated that a modified KTiOPO4 (KTP) crystal can be used to mediate multiple nonlinear optical processes simultaneously, potentially allowing it to act as the heart of a many-mode CV entanglement source. The generation of two CV-entangled modes (bipartite entanglement) is accomplished by first creating two “squeezed” beams in an optical parametric oscillator (OPO) operating just below threshold. These beams, which display reduced fluctuations in one particular phase combination of the electric and magnetic field, are next overlapped on a 50/50 beam splitter. The two output beams of the beam splitter are CV-entangled and can be used for quantum encryption or quantum teleportation. To increase the number of parties participating in the encryption or teleportation scheme, researchers at the University of Tokyo recently built a tripartite (three-mode) CV entanglement source using three separate OPOs whose outputs were made to stably overlap on multiple 50/50 beam splitters. Earlier work by Pooser, Pfister, and their colleagues showed that tripartite CV entanglement could be achieved using only a single OPO, if the nonlinear crystal at the heart of the OPO could be engineered to constructively enhance, or phase-match, two different nonlinear optical interactions simultaneously. For the study reported in Optics Letters, Pooser and Pfister used a 7 mm crystal of periodically poled KTP with a carefully chosen 45.65 μm period. As predicted by theory, when pumped with light at 1.49 μm, the crystal displayed simultaneous phase-matching for three independent nonlinear processes (two second-harmonic generation processes and one sum-frequency generation process), sufficient in principle for as much as quadripartite (four-mode) CV entanglement. This rare “triple coincidence” suggests that complex multipartite CV entanglement sources based on only a single OPO are feasible with the appropriate crystal engineering. Such sources could ultimately become critical components in applied quantum encryption and quantum teleportation systems. COLIN MCCORMICK
SAMs Serve as Templates for Patterned Growth of Large Oriented Organic Semiconductor Single Crystals Organic electronic devices fabricated from high-quality single crystals of organic semiconductors have increased mobility due to the lack of grain boundaries and molecular disorder. One of the challenges that limits application of single-crystalline organic semiconductors is the fragility of the crystals, which creates problems in handling them. If the oriented single-crystalline organic semiconductor could be selectively grown directly in the designated locations in a device structure, this problem could be solved. Recently, a group of researchers in the University of California at Los Angeles, Lucent Technology, and Stanford University have made progress toward this goal. As reported in the September issue o
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