A. A. Nikulin

Observation of hybrid state of Tamm and surface plasmon-polaritons in one-dimensional photonic crystals

Experimental observation of hybrid mode of Tamm plasmon-polariton and surface plasmon-polariton is reported. The hybrid state is excited in one-dimensional photonic crystal terminated by semitransparent metal film under conditions of total internal reflection for transverse-magnetic-polarized light. Coupling between Tamm and surface plasmon-polaritons leads to repulsion of their dispersion curves controlled by metal film thickness.

Second-harmonic generation in metal and semiconductor low-dimensional structures

Abstract In this article previous and recent results of our nonlinear optical studies of low-dimensional structures are surveyed. Size effect in the optical second-harmonic generation (SHG) from Ag nanocrystals in island films and CdSe quantum dots in glass matrices as well as thermo- and DC-electric-field-induced effects in SHG from SiSiO2 multiple quantum wells (MQWs) on Si substrate are studied experimentally and theoretically. Essential (by several orders of magnitude) enhancement of quadratic optical response upon decrease in the particle size is observed for both Ag nanocrystals and CdSe quantum dots. Regular oscillations in the second-harmonic intensity measured as functions of temperature and applied DC electric field are observed for MQWs. It is shown that the size effect for metal nanocrystals can result from the fluctuations of the particle size breaking the local inversion symmetry. Another mechanism studied (based on concepts of dynamic chaos) describes the observed size effects for both metal and semiconductor particles. The dependence of the second-harmonic intensity on the SiO2 layer thickness in MQWs is described with taking into account the retardation of the second-harmonic radiation in MQWs, whereas the thermoinduced effect is interpreted as resulting from the optical interference in the MQWs substrate having thickness dependent on temperature (due to the thermal expansion). A possible approach to explaining the observed electroinduced effect in MQWs is also discussed.

Electromagnetic mechanism of surface enhanced second harmonic generation by “smooth” silver electrodes and scanning tunneling microscopy

Abstract The surface of originally smooth silver electrodes is studied by means of reflected second harmonic (SH) generation and scanning tunneling microscopy after electrochemical etching of N monoatomic surface layers ( N ∼ 0minus;10). At N ∼ 1 a generation of surface enhanced, diffuse, and depolarized SH is observed, and a distinct superatomic (of the scale ∼ 10 A) granular roughness is detected on the electrode surface. The fluctuation electromagnetic mechanism is proposed to explain the surface enhancement of diffuse and depolarized SH component: the effect is interpreted as resulting from exciton of local plasmons in irregular surface structures formed in the process of etching.

The electromagnetic classical mechanism of surface enhanced second harmonic generation and Raman scattering in Island films

Abstract The nature of the surface enhancement of second harmonic generation in silver island films is studied experimentally and theoretically. The electromagnetic contribution to the surface enhancement is selected by the controllable variation of parameters of the surface plasmon resonance in silver particles evaporated onto a dielectric wedge coating a semiconductor substrate layer. The relative enhancement of the second harmonic intensity due to the surface plasmon resonance is ∼ 150, what gives an estimate ∼ 2·104 for the analogous contribution to the surface enhancement of Raman scattering. The behaviour of the surface plasmon resonance is found to be weakly dependent on the dissipative properties of the layer. The experimental data are in good agreement with the numerical results.

The new mechanism of surface-enhanced second harmonic generation in small metallic particles

Abstract A surface enhancement factor growth over 4 orders of magnitude is observed for the second harmonic generation from metallic particles of 10 A radius. The effect can be explained by a specific mechanism, originating from the irregular distortions of the shapes of the particles.

Plasmonic and magnetic effects accompanying optical second-harmonic generation in Au/Co/Au nanodisks

Optical second-harmonic (SH) generation in Au/Co/Au sandwich-like nanodisks is studied, using several experimental techniques, at SH frequency being close to that of the plasmon resonance in the system. The dependences of the relative amplitude and phase of the magnetization-induced SH component on the angle of incidence are found to significantly differ from those measured for a continuous Au/Co/Au trilayer film. A phenomenological description of the observed effects is proposed, with special emphasis on resonant excitation of the local plasmon modes by the nonlinear sources induced in the nanodisks.

Interferometry of hyper-Rayleigh scattering by inhomogeneous thin films

The use of specific symmetry properties of optical second-harmonic generation (the s, s-exclusion rule) has allowed us to observe high-contrast hyper-Rayleigh interference patterns in completely diffuse light, an effect that has no analog in the case of linear (Rayleigh) scattering.

Surface enhanced second harmonic generation in cold deposited silver films and scanning tunneling microscopy

Abstract The nature of surface enhancement in cold deposited silver films (CDF) is studied by means of reflected second harmonic (RSH) generation and scanning tunneling microscopy. A strong dependence of RSH radiation intensity, polarization and angular distribution on film mass thickness and temperature is observed. The surface enhancement vanishes irreversibly in CDF heated up to >220 K. Intercrystallite fractures (pores) are detected in the structure of annealed films. This residual porosity is interpreted as a result of self-diffusion healing of deeper fractures. The experimental results confirm that in CDF the surface enhancement has a ″classical ″ electromagnetic origin and is due to intercrystallite pores with sufficiently small values of the width/depth ratio. A simple theoretical model is proposed to estimate analytically the enhancement in structures such as deep narrow crevices.

Surface-enhanced Second-harmonic Generation in C60-coated Silver Island Films

Abstract Surface-enhanced generation of the diffuse and depolarized optical harmonic (SH) upon reflection of laser radiation from C60-coated silver island films is observed. An order of magnitude relative enhancement of the SH response from the coated films with respect to the uncoated ones is found. The nature of the observed effects is discussed.

Second- and third-harmonic generation and hyper-Rayleigh scattering in porous-silicon-based photonic microcavities

Optical second-harmonic (SH) generation in porous-silicon-based photonic microcavities is observed in the form of hyper-Rayleigh scattering (HRS), with the SH radiation being diffuse and depolarized. Infiltration of sodium nitrite into the pores essentially suppresses HRS and results in generation of specular and partially polarized SH. Dissimilarly, the third-harmonic (TH) radiation from both unfilled and infiltrated samples is specular and polarized. These results indicate different spatial localization of the SH and TH sources.