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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - All-Optical Ultrafast Control of Second Harmonic Generation in AlGaAs Nanopillars
摘要： All-dielectric nanophotonics has recently raised an increasing interest because the optical response of high-permittivity dielectric nanoparticles exhibits negligible dissipative losses and strong magnetic multipole resonances [1-4] in the visible and near-IR. We recently reported a second harmonic generation (SHG) conversion efficiency higher than 10-5 at (cid:79)= 1554 nm (pump intensity (cid:124) 1.6 GW/cm2; pulse width (cid:124) 150 fs; repetition rate = 80 MHz) in all-dielectric Al0.18Ga0.82As-on-AlOx nanodisks [5-7]. Such a remarkable efficiency is achieved thanks to the exploitation of magnetic and electric resonances emerging at coincidence with both the pump and SHG wavelength. In addition, the choice of both the pump and, consequently, the SHG ((cid:124) 777 nm) wavelength, set below the energy of the material bandgap, allow minimizing the two-photon absorption of the pump and the re-absorption of the SHG. Here, we demonstrate the potential for the all-optical modulation of the SHG. First, we study the behavior of the emitted SHG signal when the nanoantennas are concurrently illuminated with a low-power (< 300 (cid:80)W) continuous wave (CW) laser with energy above the bandgap ((cid:124) 3.2 eV, 405 nm wavelength). We observe variations in the SHG yield of the nanoantennas up to 60%. Figure 1a shows the SHG differential map acquired on an array of nanopillars with variable radius (r). Figure 1b shows the overall SHG intensity (dashed line) as well as the SHG modulation (solid blue line) as a function of r. While SHG from the smaller nanopillar (r = 205 nm) is decreased by about 60% under a 300 (cid:80)W CW pump beam, the 220-nm-radius nanopillar show a 30% SHG enhancement. We also investigated the ultrafast modulation of the SHG in a pump-probe experiment, where the pump is an ultrashort pulse at (cid:79)= 510 nm (above material bandgap), while the probe is a time-delayed pulse at (cid:79)= 1550 nm generating the SHG, to study the SHG dynamics when the pillars are brought out of equilibrium and a transient plasma is photoinjected in the dielectric. Time-traces of the SHG as a function of the pump-probe delay are shown in Figure 1c. We measured an ultrafast SHG quenching (< 0.5 ps) and slower (10 to 100 ps) recovery times, which strongly depend on the nanopillars, hence on the resonances involved. Our results allow gaining further insight into the photophysics of the nonlinear emission in these nanoscale systems and pave the way to the all-optical control of nanoscale nonlinear photonic devices for data storage with AlGaAs-on-insulator all-dielectric platforms.
关键词： Second harmonic generation,All-optical modulation,Nanopillars,All-dielectric nanophotonics,AlGaAs,SHG
更新于2025-09-12 10:27:22
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Dewetting mechanisms and their exploitation for the large-scale fabrication of advanced nanophotonic systems
摘要： Recent progress in submicron- and nano-fabrication technologies has led to the emergence of novel photonic structures such as optical nanoantennas and metasurfaces. Real-life applications of these advanced photonic structures still require substantial improvement of the fabrication processes, in terms of their throughput and cost-effectiveness. Because of its simplicity and effectiveness, dewetting of a thin film has attained increasing attention as a feasible process for improving the scalability and productivity. Here, we provide an overview of the mechanisms and phenomenologies of dewetting to foster an improved fundamental understanding necessary for the optimisation of the dewetting process condition and template design. We then review the strategies demonstrating the use of templated-dewetting for producing well-aligned arrays of submicron- and nanostructures with great control over their size, shape and arrangement. Recent applications of dewetted structures in advanced nanophotonics are reviewed with an emphasis on the exploitation of dewetting mechanisms. Special attention is given to the fabrication of resonant optical nanoantennas and nanophotonic applications in which high repeatability and throughput are important parameters: sensing, colourisation, photovoltaics and nonlinear light frequency conversion. We expect this review to provide a basis for the use of thin-film dewetting to realise the industrial-level fabrication of various practical advanced photonic systems.
关键词： optical nanoantenna,interfacial instability,plasmonics,all-dielectric nanophotonics,nanofabrication,advanced photonic applications,Dewetting,thin film
更新于2025-09-04 15:30:14