Abstract We experimentally demonstrate modulation of reflectance in periodic arrays of subwavelength gallium arsenide nanocylinders with Mie-type resonances due to absorption saturation and changes in the refractive index of the semiconductor material of metasurface. The intensity-dependent reflectance modulation of up to 30% in the vicinity of the magnetic dipole resonance at a low laser fluence below 200 μ J/cm 2 is shown by I-scan measurements

Brener, Igal

Dolgova, Tatyana V

Fedotova, Anna A

Fedyanin, Andrey A

Keeler, Gordon A

Liu, Sheng

Shcherbakov, Maxim R

Shorokhov, Alexander S

Staude, Isabelle

Vabishchevich, Polina P

Zubyuk, Varvara V

English

Digitale Bibliothek Thüringen

1Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distributionof this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.Published under licence by IOP Publishing Ltd1234567890 ‘’“”METANANO 2018 IOP PublishingIOP Conf. Series: Journal of Physics: Conf. Series 1092 (2018) 012181  doi :10.1088/1742-6596/1092/1/012181Intensity-dependent reflectance modulationof femtosecond laser pulses in GaAs nanocylinderswith magnetic resonancesVarvara V Zubyuk1, Polina P Vabishchevich1,2,3,Maxim R Shcherbakov1,4, Alexander S Shorokhov1,Anna A Fedotova1,5, Sheng Liu2,3, Gordon A Keeler2,Tatyana V Dolgova1, Isabelle Staude5, Igal Brener2,3 andAndrey A Fedyanin11 Quantum Electronics Department and Quantum Technology Center, Faculty of Physics,Lomonosov Moscow State University, Moscow 119991, Russia2 Sandia National Laboratories, Albuquerque, New Mexico 87185, United States3 Center for Integrated Nanotechnologies, Sandia National Laboratories, Albuquerque, NewMexico 87185, USA4 School of Applied and Engineering Physics, Cornell University, Ithaca, NY 14853, USA5 Institute of Applied Physics, Abbe Center of Photonics, Friedrich-Schiller-University Jena,07743 Jena, GermanyE-mail: zubyuk@nanolab.phys.msu.ru, fedyanin@nanolab.phys.msu.ruAbstract. We experimentally demonstrate modulation of reflectance in periodic arrays ofsubwavelength gallium arsenide nanocylinders with Mie-type resonances due to absorptionsaturation and changes in the refractive index of the semiconductor material of metasurface.The intensity-dependent reflectance modulation of up to 30% in the vicinity of the magneticdipole resonance at a low laser fluence below 200 μJ/cm2 is shown by I-scan measurements.1. IntroductionPhenomenon of saturable absorption of semiconductors is widely used in optical devices suchas semiconductor saturable absorber mirror (SESAM) [1]. These devices have become a keycomponent of ultrafast passively mode-locked and Q-switched laser sources [2, 3]. The saturationof optical absorption was demonstrated in different materials and systems such as plasmonicnanocomposites [4, 5]. Recently, semiconductor nanoparticles and metasurfaces with Mie-typeresonance have proven themselves as potentially useful for nanophotonic applications [6, 7]. Thishappened since they possess completely new properties in comparison with bulk materials [8, 9]and reveal enhanced interaction with electromagnetic radiation [10, 11]. The dielectricmetasurfaces also demonstrate low absorption losses as compared to plasmonic structures. Inthis work, we experimentally demonstrate the intensity-dependent reflectance modulation offemtosecond laser pulses in GaAs nanocylinders samples that exhibit the Mie-type resonances.21234567890 ‘’“”METANANO 2018 IOP PublishingIOP Conf. Series: Journal of Physics: Conf. Series 1092 (2018) 012181  doi :10.1088/1742-6596/1092/1/012181Figure 1. (a) A scanning electron microscope image of the GaAs metasurface. (b) Reflectionspectra of the GaAs nanocylinders sample with a magnetic dipole (MD) resonant peakat λ ∼ 880 nm for p- and s-polarization of the incident laser radiation at θ = 12◦.2. Results and discussion2.1. Metasurface sampleThe samples are periodic arrays of GaAs nanocylinders with silica caps on top, nanocylinderssituated on AlGaO nanocylinders that are situated on a bulk GaAs substrate (Fig.1(a)). Themetasurface was fabricated using a previously published procedure [11, 12]. The diameter andheight of the nanocylinders are 200 nm and 300 nm, respectively, the diameter-to-pitch ratiois 0.5, and the height of the AlGaO nanocylinders is also approximately 300 nm. Measuredreflectance spectra of GaAs nanocylinders arrays at θ = 12◦ are close to the normal angle ofincidence and exhibit peaks both for p- and s-polarized light that correspond to the magneticdipole (MD) resonance at the same wavelength in the near infrared (Fig.1(b)). The MDresonance for p-polarized light shifts to the long-wavelength range as the angle of incidenceis increased.2.2. I-scan measurementsWe measure the intensity of femtosecond laser pulses that are reflected from the GaAsmetasurface using I-scan measurements in reflection geometry. The wavelength λ = 830 nm is setnot far from the bandgap of GaAs (λ = 870 nm) to maximize the effect of absorption saturation.This laser radiation generates electron-hole pairs due to the single photon absorption processes.The free carrier plasma affects the complex dielectric permittivity; the intensity-dependentreflectance is detected at the normal angle of incidence. The GaAs sample shows the enhancedmodulation order of magnitude larger in comparison with the GaAs substrate (Fig.2(a)). Thereflectance coefficient as a function of the incident laser intensity for the GaAs nanocylinderssample is indicated by black dots and for the substrate by blue dots. We demonstrate intensity-dependent laser pulse modulation of up to 30% in the vicinity of the magnetic dipolar resonanceat a low pump fluence below 200 μJ/cm2. We found excellent agreement of the experimentalresults with fullwave simulations that use a model with changes in the complex dielectricpermittivity induced by free carriers.31234567890 ‘’“”METANANO 2018 IOP PublishingIOP Conf. Series: Journal of Physics: Conf. Series 1092 (2018) 012181  doi :10.1088/1742-6596/1092/1/012181Figure 2. (a) Reflectance coefficient as a function of the incident laser intensity for the GaAsnanocylinders sample (black dots) and for substrate (blue dots). (b) Different contribution to thechanges in extinction coefficient as a function of the incident laser intensity for the GaAs materialinduced by free carriers: BF – bandfilling contribution, BS – bandgap shrinkage contribution,Dt – Drude term and Total contribution (Total=BF+BS+Dt).2.3. Reflectance modulation mechanismThe laser radiation generates electron-hole pairs due to the single photon absorption processesand this leads to the changes in the complex dielectric permittivity. We provided the full-wavesimulations with different changes in complex refractive index and find out that reflectancemodulation occurs mainly due to changes in extinction coefficient. These changes are determinedby three contributions [13] and total change become negative:Δκ = ΔκBF +ΔκBS +ΔκDt < 0, (1)where the indexes of ΔκBF,BS,Dt correspond to BF – bandfilling contribution, BS – bandgapshrinkage contribution, Dt – Drude term and Δκ is the total changes: Total=BF+BS+Dt. Themain contribution to the total change is made by the bandfilling. The reflectance spectrum of theGaAs metasurface is strongly modified under intense laser radiation due to the high sensitivityof Mie-type resonance to material parameters.3. ConclusionsIn conclusion, we have experimentally demonstrated intensity-dependent reflectance modulationof the laser pulse in subwavelength GaAs nanocylinders exhibiting localized Mie-type resonances.The modulation of reflectance coefficient is up to 30% and occurs under free carriers generationat a low laser fluence below 200 μJ/cm2. The reflectance modulation mechanism is complex andis determined primarily by absorption changes due to bandfilling effect.AcknowledgmentsThis work was partly supported by financial support from Ministry of Education and Science ofthe Russian Federation (grant N14.W03.31.0008, calculation of optical spectra). Experimentalpart was performed with the support of the grant of the President of the Russian Federationfor leading scientific schools (grant No. NSh-6862.2018.2 — optical spectra), supported inpart by Russian National Technology Initiative, Russian Foundation for Basic Research (grantNo. 16-29-11811 — I-scan measurements), and by the German Research Foundation throughthe Emmy Noether Programme (STA 1426/2-1). Parts of this work were supported by the41234567890 ‘’“”METANANO 2018 IOP PublishingIOP Conf. Series: Journal of Physics: Conf. Series 1092 (2018) 012181  doi :10.1088/1742-6596/1092/1/012181U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciencesand Engineering and performed, in part, at the Center for Integrated Nanotechnologies, anOffice of Science User Facility operated for the U.S. Department of Energy (DOE) Office ofScience. Sandia National Laboratories is a multi-mission laboratory managed and operated byNational Technology and Engineering Solutions of Sandia, LLC, a wholly owned subsidiary ofHoneywell International, Inc., for the U.S. Department of Energys National Nuclear SecurityAdministration under contract DE-NA0003525.References[1] Keller U et al. 1996 IEEE J. Sel. Top. Quantum Electron. 2 435–451[2] Keller U 2003 Nature 424 831[3] Saraceno C et al. 2012 IEEE J. Sel. Top. Quantum Electron. 18 29–41[4] Plaksin O et al. 2008 J. Appl. Phys. 103 114302[5] Kumar M et al. 2014 Plasmonics 9 129–136[6] Shcherbakov M et al. 2015 Nano Lett. 15 6985–6990[7] Shcherbakov M et al. 2017 Nat. Commun. 8 17[8] Evlyukhin A B et al. 2012 Nano Lett. 12 3749–3755[9] Decker M et al. 2015 Adv. Opt. Mat. 3 813–820[10] Shorokhov A et al. 2016 Nano Lett. 16 4857–4861[11] Liu S et al. 2016 Nano Lett. 16 5426–5432[12] Liu S et al. 2016 Adv. Opt. Mat. 10 1457–1462[13] Bennett B et al. 1990 IEEE J. Quantum Electron. 26 113–122

Intensity-dependent reflectance modulation of femtosecond laser pulses in GaAs nanocylinders with magnetic resonances

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Intensity-dependent reflectance modulation of femtosecond laser pulses in GaAs nanocylinders with magnetic resonances

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