Efficient frequency conversion techniques are crucial to the development of plasmonic metasurfaces for information processing and signal modulation. In principle, nanoscale electricfield confinement in nonlinear materials enables higher harmonic conversion efficiencies per unit volume than those attainable in bulk materials. Here we demonstrate efficient secondharmonic generation (SHG) in a serrated nanogap plasmonic geometry that generates steep electric field gradients on a dielectric metasurface. An ultrafast pump is used to control plasmon-induced electric fields in a thin-film material with inversion symmetry that, without plasmonic enhancement, does not exhibit an an even-order nonlinear optical response. The

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The identification of the capture mechanism of charge c a r r i e r s by centers with attractive Coulomb potential proceeding from the temperature dependence of the recombination coefficient only sometimes is ambiguous. Fig. 1 shows the temperature dependence of the capture coefficient of holes a) for defects with the Ec -0.20 eV level in T-irradiated 6oCo Sb-doped Ge obtained from measurements of the steady-state photomagnetoelectric effect (PME) /l/. This dependence was analyzed within the framework of two models, i. e. cascades involving the longwave acoustic phonon /2, 3/ and optical phonon emission /4/.In the f i r s t c a s e the temperature dependence of the recombination coefficient is described by the power law P r ( T ) -T n . The experimental value of r as a function of 1 0 /T was processed ac-P cording to (1) and (2) by the least squares method using a computer. The results obtained are presented by the solid lines T 1) 5.6xlO T-4'1 (curve 1 ) and f = 3.26 T satisfactory agreement with the experimental data. 2 -1.5 P exp(0.03/kT) (curve 2 ) in Fig. 1. These curves are in P Additional information for a more accurate estimation of recombination models may be obtained by investigating the r dependence upon the uniaxial p r e s s u r e P /5, 6/. We investigated the PME voltage with p r e s s u r e in irradiated n-type germanium at 90 K when the lifetime of excess holes was P 1 ) 220080 Minsk, USSR.9 physica (bJ

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