Photoluminescence and spectral switching of single CdSe/ZnS colloidal nanocrystals in poly(methyl methacrylate)

Emission from single CdSe nanocrystals in PMMA was investigated. A fraction of the nanocrystals exhibiting switching between two energy states, which have similar total intensities, but distinctly different spectra were observed. We found that the spectral shift characteristic frequency increases with the pump power. By using the dynamic shift in the spectral position of emission peaks, we were able to correlate peaks from the same nanocrystal. The measured correlation is consistent with assignment of low energy lines to phonon replicas.Comment: 5 pages, 4 figure

Luminescent hyperbolic metasurfaces.

When engineered on scales much smaller than the operating wavelength, metal-semiconductor nanostructures exhibit properties unobtainable in nature. Namely, a uniaxial optical metamaterial described by a hyperbolic dispersion relation can simultaneously behave as a reflective metal and an absorptive or emissive semiconductor for electromagnetic waves with orthogonal linear polarization states. Using an unconventional multilayer architecture, we demonstrate luminescent hyperbolic metasurfaces, wherein distributed semiconducting quantum wells display extreme absorption and emission polarization anisotropy. Through normally incident micro-photoluminescence measurements, we observe absorption anisotropies greater than a factor of 10 and degree-of-linear polarization of emission >0.9. We observe the modification of emission spectra and, by incorporating wavelength-scale gratings, show a controlled reduction of polarization anisotropy. We verify hyperbolic dispersion with numerical simulations that model the metasurface as a composite nanoscale structure and according to the effective medium approximation. Finally, we experimentally demonstrate >350% emission intensity enhancement relative to the bare semiconducting quantum wells

Somatostatin Is Expressed in FRTL-5 Thyroid Cells and Prevents Thyrotropin-Mediated Down-Regulation of the Cyclin-Dependent Kinase Inhibitor p27kip11

9 pages, 8 figures, 3 tables.Using RT and amplification, we have detected specific RNA transcripts encoding somatostatin in FRTL-5 thyroid cells. This observation indicates that within the thyroid context, expression of somatostatin is not restricted to the parafollicular C cells. Transfection of FRTL-5 cells with constructs containing either the complete somatostatin gene promoter or deletions carrying the cAMP response element-binding site allowed us to demonstrate that transcription of the somatostatin gene is hormonally regulated by TSH. Blockage of somatostatin by specific antibodies resulted in an increased capacity of TSH-induced FRTL-5 cell-conditioned medium to promote cell proliferation, demonstrating that under physiological conditions, somatostatin exerts a cytostatic effect on FRTL-5 cells growth. Somatostatin treatment of FRTL-5 cells resulted in a growth retardation, caused by a dose-response delay in the G1 phase of the cell cycle. This effect appears to be mediated by the cyclin-dependent kinase inhibitor p27kip1, which is clearly down-regulated in FRTL-5 cells treated with TSH and whose expression is reestablished by somatostatin in a dose-dependent manner. Participation of somatostatin in the control of FRTL-5 cell proliferation is in agreement with the detection of specific somatostatin receptor type 2. Flow cytometric assays reveal that FRTL-5 cells transformed with the K-ras oncogene are still sensitive to somatostatin treatment, whereas fully neoplastic FRT cells no longer respond to this peptide. Taking together, the results demonstrate the participation of an autocrine loop in the control of thyroid cell proliferation, and the possibility that this mechanism could be altered in the process of thyroid carcinogenesis.This work was supported by Grants DGICYT (PM97–0065), CAM (08.1/0025/1997), and Fundación Salud 2000 (Spain).Peer reviewe

All-optical control of ferromagnetic thin films and nanostructures

The interplay of light and magnetism has been a topic of interest since the original observations of Faraday and Kerr where magnetic materials affect the light polarization. While these effects have historically been exploited to use light as a probe of magnetic materials there is increasing research on using polarized light to alter or manipulate magnetism. For instance deterministic magnetic switching without any applied magnetic fields using laser pulses of the circular polarized light has been observed for specific ferrimagnetic materials. Here we demonstrate, for the first time, optical control of ferromagnetic materials ranging from magnetic thin films to multilayers and even granular films being explored for ultra-high-density magnetic recording. Our finding shows that optical control of magnetic materials is a much more general phenomenon than previously assumed. These results challenge the current theoretical understanding and will have a major impact on data memory and storage industries via the integration of optical control of ferromagnetic bits.Comment: 21 pages, 11 figure

Thermal Considerations In Electrically-pumped Metallo-dielectric Nanolasers

Metal nanocavity-based lasers show promise for dense integration in nanophotonic devices, thanks to their compact size and lack of crosstalk. Thermal considerations in these devices have been largely overlooked in design, despite the importance of self-heating and heat dissipation to device performance. We discuss the sources of self-heating in electrically-pumped wavelength-scale nanolasers, and the incorporation of these heat sources into a heat dissipation model to calculate laser operating temperature. We apply this thermal model to an example electrically-pumped nanolaser operating at room temperature. © 2014 SPIE.8980The Society of Photo-Optical Instrumentation Engineers (SPIE)Lee, J.H., Khajavikhan, M., Simic, A., Gu, Q., Bondarenko, O., Slutsky, B., Nezhad, M.P., Fainman, Y., Electrically pumped sub-wavelength metallo-dielectric pedestal pillar lasers (2011) Optics Express, 19, pp. 21524-21531. , OctDing, K., Ning, C.Z., Fabrication challenges of electrical injection metallic cavity semiconductor nanolasers (2013) Semiconductor Science and Technology, 28, p. 124002. , NovHill, M.T., Oei, Y.-S., Smalbrugge, B., Zhu, Y., De Vries, T., Van Veldhoven, P.J., Van Otten, F.W.M., Smit, M.K., Lasing in metallic-coated nanocavities (2007) Nature Photonics, 1, pp. 589-594. , SeptNezhad, M.P., Simic, A., Bondarenko, O., Slutsky, B., Mizrahi, A., Feng, L., Lomakin, V., Fainman, Y., Room-temperature subwavelength metallo-dielectric lasers (2010) Nature Photonics, 4, pp. 395-399. , AprKhajavikhan, M., Simic, A., Katz, M., Lee, J.H., Slutsky, B., Mizrahi, A., Lomakin, V., Fainman, Y., Thresholdless nanoscale coaxial lasers (2012) Nature, 482, pp. 204-207. , JanGu, Q., Slutsky, B., Vallini, F., Smalley, J.S.T., Nezhad, M.P., Frateschi, N.C., Fainman, Y., Purcell effect in sub-wavelength semiconductor lasers (2013) Optics Express, 21 (13), p. 15603Ning, C.Z., What is Laser Threshold (2013) IEEE Journal of Selected Topics in Quantum Electronics, 19, pp. 1503604-1503604. , MayHess, O., Pendry, J.B., Maier, S.A., Oulton, R.F., Hamm, J.M., Tsakmakidis, K.L., Active nanoplasmonic metamaterials (2012) Nature Materials, 11, pp. 573-584. , JulyDing, K., Hill, M.T., Liu, Z.C., Yin, L.J., Van Veldhoven, P.J., Ning, C.Z., Record performance of electrical injection sub-wavelength metallic-cavity semiconductor lasers at room temperature (2013) Optics Express, 21 (4), pp. 4728-4733Hobson, W.S., Mohideen, U., Pearton, S.J., Slusher, R.E., Ren, F., SiN x/sulphide passivated GaAs/AlGaAs microdisk lasers (1993) Electronics Letters, 29 (25), pp. 2199-2200Ding, K., Ning, C.Z., Metallic subwavelength-cavity semiconductor nanolasers (2012) Light: Science & Applications, 1, pp. e20. , JulyNing, C.Z., Indik, R.A., Moloney, J.V., Self-consistent approach to thermal effects in vertical-cavity surface-emitting lasers (1995) JOSA B, 12 (10), pp. 1993-2004Smalley, J.S.T., Gu, Q., Fainman, Y., Temperature dependence of the spontaneous emission factor in subwavelength semiconductor lasers (2014) IEEE Journal of Quantum Electronics, 50, pp. 175-185. , MarYu, S.F., (2003), Analysis and design of vertical cavity surface emitting lasers, Wiley - 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Folded shift multiplexing

Shift multiplexing is a holographic recording method that uses a spherical reference wave. We extend the principle to a thin slab of holographic material that acts as a waveguide. Total internal reflection folds the reference spherical beam in one dimension. We demonstrate that the shift selectivity with the folded spherical beam is independent of the slab thickness but depends instead on the numerical aperture of the coupled spherical wave. A shift selectivity of 0.5 mum has been achieved with a 1-mm-thick LiNbO3 crystal and 50 high-definition data pages are recorded with this method. (C) 2003 Optical Society of America

Hybrid multimode resonators based on grating-assisted counter-directional couplers

FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPResearch thrusts in silicon photonics are developing control operations using higher order waveguide modes for next generation high-bandwidth communication systems. In this context, devices allowing optical processing of multiple waveguide modes can reduce architecture complexity and enable flexible on-chip networks. We propose and demonstrate a hybrid resonator dually resonant at the 1st and 2nd order modes of a silicon waveguide. We observe 8 dB extinction ratio and modal conversion range of 20 nm for the 1st order quasi-TE mode input.25141648416490FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP2015/20525-6Office of Naval Research (ONR) Multi-Disciplinary Research Initiative; National Science Foundation (NSF) (NNCI-SDNI, ERC CIAN); Defense Advanced Research Projects Agency (DARPA); Army Research Office (ARO); Cymer Corporation. M. Souza acknowledges FAPESP (grant 2015/20525-6)

Intrinsic Entanglement Degradation by Multi-Mode Detection

Relations between photon scattering, entanglement and multi-mode detection are investigated. We first establish a general framework in which one- and two-photon elastic scattering processes can be discussed, then we focus on the study of the intrinsic entanglement degradation caused by a multi-mode detection. We show that any multi-mode scattered state cannot maximally violate the Bell-CHSH inequality because of the momentum spread. The results presented here have general validity and can be applied to both deterministic and random scattering processes.Comment: 12 pages, 4 figures, v3: minor changes. Phys. Rev. A (2004), to be publishe