3Rd-Order Nonlinearity Of 4-Dialkylamino-4\u27Nitro-Stilbene Wave-Guides At 1319 Nm

The intensity dependent optical properties of 4-dialkylamino-4\u27nitro-stilbene polymer channel waveguides were measured at 1319 nm with a pulse modulated Mach-Zehnder interferometer to be n2 = 0.8 x 10(-13) cm2/W and beta2 \u3c 0.08 cm/GW. This material is promising for all-optical switching at 1319 nm because it satisfies both the W and T figures of merit

Cascaded second-order nonlinearities in waveguides.

The cascaded second-order nonlinearity arising from the second-harmonic generation process in noncentrosymmetric media is a novel approach to achieving the nonlinear phase shifts required for all-optical signal processing. The research presented in this dissertation demonstrated and measured the cascaded second-order nonlinearity for the first time in viable integrated optical waveguide formats. Cascaded self-phase modulation was measured in potassium titanyl phosphate (KTiOPO₄ or KTP) segmented quasi-phasematched waveguides at wavelengths near 855 nm and in the optical fiber telecommunications window near 1.585 μm using picosecond and femtosecond pulses, respectively. Spectral modulation and broadening were observed on the output fundamental spectrum and compared to predictions from pulsed second-harmonic generation theory under conditions of group-velocity mismatch (temporal walk-off) and group-velocity dispersion. Peak cascaded phase shifts of the fundamental of approximately π at 855 nm were inferred with 690 W of peak guided power. Peak cascaded phase shifts of approximately π/2 were inferred at 1.585 μm with 760 W of peak power in the guide. Direct interferometric measurements of the magnitude and sign of the cascaded nonlinear phase shift of the fundamental were performed in temperature-tuned lithium niobate (LiNbO₃) channel waveguides at 1.32 μm. The cascaded phase shift was shown to change sign upon passing through the phasematching condition, as required by theory. Peak cascaded phase shifts of +0.53π and -0.13π were measured for 86 W peak power in these waveguides. A non-uniform temperature profile along the waveguide led to a non-uniform wavevector-mismatch along the guide, resulting in an enhanced positive phase shift and an increased temperature bandwidth for the phase shift. The phase shifts achieved in this research are large enough to be suitable for some all-optical signal processing functions

Temperature limits in laser cooling of free atoms with three-level cascade transitions

FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOFACEPE - FUNDAÇÃO DE AMPARO À CIÊNCIA E TECNOLOGIA DO ESTADO DE PERNAMBUCOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOWe employ semiclassical theoretical analysis to study laser cooling of free atoms using three-level cascade transitions, where the upper transition is much weaker than the lower one. This represents an alternate cooling scheme, particularly useful for group II atoms. We find that temperatures below the Doppler limits associated with each of these transitions are expected. The lowest temperatures arise from a remarkable increase in damping and reduced diffusion compared to two-level cooling. They are reached at the two-photon resonance, where there is a crossing between the narrow and the partially dark dressed states, and can be estimated simply by the usual Doppler limit considering the decay rate of the optical coherence between these states.We employ semiclassical theoretical analysis to study laser cooling of free atoms using three-level cascade transitions, where the upper transition is much weaker than the lower one. This represents an alternate cooling scheme, particularly useful for group II atoms. We find that temperatures below the Doppler limits associated with each of these transitions are expected. The lowest temperatures arise from a remarkable increase in damping and reduced diffusion compared to two-level cooling. They are reached at the two-photon resonance, where there is a crossing between the narrow and the partially dark dressed states, and can be estimated simply by the usual Doppler limit considering the decay rate of the optical coherence between these states.87615FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOFACEPE - FUNDAÇÃO DE AMPARO À CIÊNCIA E TECNOLOGIA DO ESTADO DE PERNAMBUCOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOFACEPE - FUNDAÇÃO DE AMPARO À CIÊNCIA E TECNOLOGIA DO ESTADO DE PERNAMBUCOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOSem informaçãoSem informaçãoSem informaçãoThis work has been supported by FAPESP, FACEPE, CNPq, and CEPOF

Visions of science and technology between graduate in Physics when using educational robotics: A case study

This study aimed to analyze visions of science and technology in graduate Physics Universidade Federal Rural de Pernambuco (UFRPE), using the educational robotics. The investigative activities were carried out in the Exact Graduate Center and Nature (CEGEN) in a class of seventh period of the course Full Degree in Physics and with the participation of eight students. The methodology for this research was used the Theory of Personal Constructs (TCP), the more accurately Kelly Experience Cycle (CEK) consists of five stages: anticipation, investment, meeting, the confirmation or refutation and constructive review. This cycle was used with the methodological tool in order to identify the and technology science views before (pre-test) and after (post-test) the contact of students with educational robotics (event). They were used as script data collection instruments interviews, the same recordings and materials prepared by the students. After analyzing the data collection instruments were identified constructs presented by students. Eight who students were part of the survey, seven of them had at least one of its constructs changed at the end of the cycle. Therefore, there was an increase in at least one deconstructs in 87.5% of the sample. From there the pre-test, were identified some science and technology visions present in the speech of students, with greater indication, decontextualized views. Post-test, there was a change of the same and the students were more likely to less traditional and more contemporary views science and technology

Optical Dielectric Function Of Silver

The dielectric function of silver is a fundamental quantity related to its electronic structure and describes its optical properties. However, results published over the past six decades are in part inconsistent and exhibit significant discrepancies. The measurement is experimentally challenging with the values of dielectric function spanning over five orders of magnitude from the mid-infrared to the visible/ultraviolet spectral range. Using broadband spectroscopic ellipsometry, we determine the complex-valued dielectric function of evaporated and template stripped polycrystalline silver films from 0.05 eV (λ=25μm) to 4.14 eV (λ=300 nm) with a statistical uncertainty of less than 1%. From Drude analysis of the 0.1-3 eV range, values of the plasma frequency ωp=8.9±0.2 eV, dielectric function at infinite frequency ε =5±2, and relaxation time τ=1/Γ=17±3 fs are obtained, with the absolute uncertainties estimated from systematic errors and experimental repeatability. Further analysis based on the extended Drude model reveals an increase in τ with decreasing frequency in agreement with Fermi liquid theory, and extrapolates to τ≃22 fs for zero frequency. A deviation from simple Fermi liquid behavior is suggested at energies below 0.1 eV (λ=12μm) with the onset of a further increase in τ connecting to the DC value from transport measurements of ∼40 fs. The results are consistent with a wide range of optical and plasmonic experiments throughout the infrared and visible/ultraviolet spectral range. However, due to the polycrystalline nature of our sample, the values measured are not likely reaching the intrinsic limit of silver. The influence of grain boundaries, defect scattering, and surface oxidation is discussed. The results are compared with our previous measurements of the dielectric function of gold [Olmon, Phys. Rev. B 86, 235147 (2012)]PRBMDO1098-012110.1103/PhysRevB.86.235147