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Hu, X., Zhong, T., White, J. E., Dauler, E. A. N., Faraz, Herder, C. H., Wong, F. N. C., et al. (2009). Fiber-coupled nanowire photon counter at 1550 nm with 24% system detection efficiency. Opt. Lett., 34(23), 3607–3609.
Abstract: We developed a fiber-coupled superconducting nanowire single-photon detector system in a close-cycled cryocooler and achieved 24% and 22% system detection efficiencies at wavelengths of 1550 and 1315 nm, respectively. The maximum dark count rate was ~1000 counts/s.
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Khosropanah P., Baryshev A., Zhang W., Jellema W., Hovenier J.N., Gao G.R., et al. (2009). Phase-locking of a 2.7-THz quantum cascade laser to a microwave reference. Optics Letters, 34, 2958–2960.
Abstract: We demonstrate the phase locking of a 2.7 THz metal–metal waveguide quantum cascade laser (QCL) to an external microwave signal. The reference is the 15th harmonic, generated by a semiconductor superlattice nonlinear device, of a signal at 182 GHz, which itself is generated by a multiplier chain (X12) from a
microwave synthesizer at ~ 15 GHz. Both laser and reference radiations are coupled into a bolometer mixer, resulting in a beat signal, which is fed into a phase-lock loop. The spectral analysis of the beat signal con-firms that the QCL is phase locked. This result opens the possibility to extend heterodyne interferometers into the far-infrared range.
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Driessen, E. F. C., Braakman, F. R., Reiger, E. M., Dorenbos, S. N., Zwiller, V., & de Dood, M. J. A. (2009). Impedance model for the polarization-dependent optical absorption of superconducting single-photon detectors. Eur. Phys. J. Appl. Phys., 47, 10701.
Abstract: We measured the single-photon detection efficiency of NbN superconducting single-photon detectors as a function of the polarization state of the incident light for different wavelengths in the range from 488 nm to 1550 nm. The polarization contrast varies from ~% at 488 nm to~0% at 1550 nm, in good agreement with numerical calculations. We use an optical-impedance model to describe the absorption for polarization parallel to the wires of the detector. For the extremely lossy NbN material, the absorption can be kept constant by keeping the product of layer thickness and filling factor constant. As a consequence, the maximum possible absorption is independent of filling factor. By illuminating the detector through the substrate, an absorption efficiency of ~0% can be reached for a detector on Si or GaAs, without the need for an optical cavity.
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Mohan, N., Minaeva, O., Goltsman, G. N., Saleh, M. F., Nasr, M. B., Sergienko, A. V., et al. (2009). Ultrabroadband coherence-domain imaging using parametric downconversion and superconducting single-photon detectors at 1064 nm. Appl. Opt., 48(20), 4009–4017.
Abstract: Coherence-domain imaging systems can be operated in a single-photon-counting mode, offering low detector noise; this in turn leads to increased sensitivity for weak light sources and weakly reflecting samples. We have demonstrated that excellent axial resolution can be obtained in a photon-counting coherence-domain imaging (CDI) system that uses light generated via spontaneous parametric downconversion (SPDC) in a chirped periodically poled stoichiometric lithium tantalate (chirped-PPSLT) structure, in conjunction with a niobium nitride superconducting single-photon detector (SSPD). The bandwidth of the light generated via SPDC, as well as the bandwidth over which the SSPD is sensitive, can extend over a wavelength region that stretches from 700 to 1500 nm. This ultrabroad wavelength band offers a near-ideal combination of deep penetration and ultrahigh axial resolution for the imaging of biological tissue. The generation of SPDC light of adjustable bandwidth in the vicinity of 1064 nm, via the use of chirped-PPSLT structures, had not been previously achieved. To demonstrate the usefulness of this technique, we construct images for a hierarchy of samples of increasing complexity: a mirror, a nitrocellulose membrane, and a biological sample comprising onion-skin cells.
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Gol'tsman, B. M., Kutasov, V. A., & Luk'yanova, L. N. (2009). Mechanism of formation of texture and its influence on the strength of thermoelectric p-Bi0.5Sb1.5Te3. Phys. Sol. St., 51(4), 747–749.
Abstract: It is established that, in preparing p-Bi0.5Sb1.5Te3 by vertical zone melting, in addition to the directional texture (characteristic of materials exhibiting a highly anisotropic growth rate) in which the cleavage planes of crystal grains are parallel to the direction of propagation of the crystallization front, other texture types can arise, in which the orientation of grain cleavage planes is ordered in a cross-sectional plane of the ingot. Two types of such textures, “radial†and “circular,†were observed. In a radial texture, the lines of intersection of grain cleavage planes with a cross-sectional plane of the ingot are oriented along radii of this cross section and, in a circular texture, these lines of intersection are oriented approximately perpendicular to a radius crossing the grain. The formation of a radial texture is associated with rotation of the ampoule with the crystallizing substance about its vertical axis causing centrifugal flows of the melt. The formation of a circular texture is associated with the orientation effect of the ampoule walls and with circular motion of the melt during torsional oscillations of the ampoule about the vertical axis. Ingots with a radial texture exhibit much lower resistance to splitting along their axis than ingots with a circular texture do. An explanation is provided for this fact.
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