Janne Laukkanen

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We demonstrate that second-harmonic generation (SHG) from arrays of non-centrosymmetric T-shaped gold nanodimers with a nanogap arises from asymmetry in the local fundamental field distribution and is not related strictly to nanogap size. Calculations show that the local field contains orthogonal polarization components not present in the exciting field,(More)
We demonstrate that the second-order nonlinear optical response of noncentrosymmetric metal nanoparticles (metamolecules) can be efficiently controlled by their mutual ordering in an array. Two samples with minor change in ordering have nonlinear responses differing by a factor of up to 50. The results arise from polarization-dependent plasmonic resonances(More)
We prepare arrays of gold nanoparticles that include both noncentrosymmetric particles with a second-order nonlinear optical response (active particles) and centrosymmetric particles with no second-order response (passive particles). The plasmon resonances of the active and passive particles are at distinct wavelengths, yet the passive particles modify the(More)
Benfeng Bai,1,* Xiangfeng Meng,1,2 Janne Laukkanen,1 Tristan Sfez,3 Libo Yu,3 Wataru Nakagawa,4 Hans Peter Herzig,3 Lifeng Li,2 and Jari Turunen1 1Department of Physics and Mathematics, University of Joensuu, P.O. Box 111, FI-80101 Joensuu, Finland 2Department of Precision Instruments, Tsinghua University, Beijing 100084, China 3Ecole Polytechnique Fédérale(More)
We present a multipolar tensor analysis of second-harmonic generation from arrays of noncentrosymmetric gold nanoparticles. In contrast to earlier results, where higher multipoles and symmetry-forbidden signals arising from sample defects play a significant role, the present results are completely dominated by symmetry-allowed electric-dipole tensor(More)
We present an extensive experimental and theoretical study of the particle plasmon resonances of L-shaped gold nanoparticles. For the small characteristic size of the particles, we observe more higher-order resonances than previously from related shapes, and show that a short-wavelength resonance arises from the particle arm width and is not the suggested(More)
UNLABELLED Ultrasmall microring and microdisk lasers with an asymmetric air/GaAs/Al0.98Ga0.02As waveguide and an active region based on InAs/InGaAs/GaAs quantum dots emitting around 1.3 μm were fabricated and studied. The diameter D of the microrings and microdisks was either 2 or 1.5 μm, and the inner diameter d of the microrings varied from 20% to 70% of(More)
We investigate the role of surface-lattice resonances (SLRs) in second-harmonic generation (SHG) from arrays of metal nanoparticles. The SLRs affect the generated signal when the sample is rotated away from normal incidence. The adjustment of the incident angle tunes the SLRs to the fundamental wavelength for SHG and improves the quality of the resonance(More)
In this article we present a radial phase mask specially designed and manufactured for direct micro-structuration under UV photolithography of a cylindrical surface covered by a photoresist TiO<sub>2</sub> film. The period of the phase mask is sub-micron (between 480 nm and 720 nm) and allows direct printing on several types of cylindrical components. With(More)