Modulation of a surface plasmon-polariton resonance by subterahertz diffracted coherent phonons

Abstract

Coherent sub-THz phonons incident on a gold grating that is deposited on a dielectric substrate undergo diffraction and thereby induce an alteration of the surface plasmon-polariton resonance. This results in efficient high-frequency modulation (up to 110 GHz) of the structure's reflectivity for visible light in the vicinity of the plasmon-polariton resonance. High modulation efficiency is achieved by designing a periodic nanostructure which provides both plasmon-polariton and phonon resonances. Our theoretical analysis shows that the dynamical alteration of the plasmon-polariton resonance is governed by modulation of the slit widths within the grating at the frequencies of higher-order phonon resonances. PACS numbers: 73.20.Mf, 78.20.hc Creating new devices based on plasmonic nanostructures (PNs) requires development of new physical concepts where the properties of plasmons and their interaction with photons may be controlled externally. Several methods of this "active plasmonics" 1,2 were reported where the energy and propagation of plasmons were controlled by temperature 3 , optical excitation 4,5 , electric 6 and magnetic fields 7-9 . In order to explore the properties of plasmons in nanodevices it is necessary to realize nondestructive control of plasmons on timescales far below 1 ns. In particular, such techniques could be employed in recently developed plasmon lasers (spasers), to enhance their functionality 10,11 . Only then the advantage of plasmonics as compared traditional integrated electronics may be indeed exploited. By now there are a number of works where ultrafast control of plasmons in PNs has been demonstrated using femtosecond optical excitation 12,13 which possess a number of undesirable side effects, like thermal heating or excitation of high-energy electron states. Besides modulation of the PN dielectric function, plasmonic states may be controlled by modulation of the geometrical parameters of the PN, like size of elements or distances between elements. This can be realized by applying uniaxial stress 14,15 and, for dynamical modulation, acoustic waves may be used. The feasibility of such an acoustic approach for the modulation of plasmonic properties has been already shown in a number of recent works, where THz phonons interact with the plasmon resonance in a very small noble metal particle 16,17 , or in periodic structures but in the frequency range up to 10 GHz 18-20 .The aim of the present work is to realize an efficient modulation by sub-THz coherent phonons in a PN which has a narrow band plasmon-polariton resonance in the k 0 E α d G o ld G a d o li n iu m G a ll iu m G a r n e t AFM-Image 750 800 850 900 4°2°6°8°1 0°D etection Glanpolarizer λ/2 t 0 =78 ns BBO Beamsplitter q=2π n/d Strain-Pulse α Regenerative Amplifier 800 nm (a) (b) (c) r h α = Augrating GGG Al x y z T=5 K Reflected intensity R 0 Wavelength (nm) [111] 400nm 0 1 2 3 FIG. 1. (a) The scheme of the sample and AFM image of the grating. (b) The reflectivity spectrum for p-polarized white light from the Au grating on G...

Terahertz dynamics of lattice vibrations in Au/CdTe plasmonic crystals: Photoinduced segregation of Te and enhancement of optical response

“…Based on these principles, surface plasmon resonant sensors for the detection of chemical and biological species are developed [3]. In addition, one can use an external stimulus such as optical excitation [4][5][6][7][8], acoustic waves [9][10][11][12] and external magnetic fields [13][14][15][16] in order to influence the dielectric function of metal and/or dielectric and subsequently to control the SPP propagation constant. Therefore, SPPs are well suited for applications in optoelectronic devices where high sensitivities * lars.kreilkamp@tu-dortmund.de and efficient optical excitation at the nanoscale are essential [8].…”

Plasmonic circuits for manipulating optical information

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Studying periodic nanostructures by probing the in-sample optical far-field using coherent phonons

“…Most of these works with coherent phonons targeted specific properties of the nanostructures by probing the electromagnetic field inside the studied nanostructure. Thus, the interaction of the vibrational phonon modes and light was studied experimentally by picosecond acoustic techniques in periodic structures which possess both photonic and phononic band gaps (i.e., photonic-phononic crystals), 9,10 hole arrays, 11 metallic gratings, [12][13][14] and complex periodic plasmonic nanostructures. 15 Less attention was paid to the elasto-optical effects that occur in bulk solid media at a distance from the nanostructure larger than the optical wavelength, where light has a well-defined wavevector and a corresponding propagation direction.…”