Pavel N. Melentiev

Giant optical nonlinearity of a single plasmonic nanostructure

We realize giant optical nonlinearity of a single plasmonic nanostructure which we call a split hole resonator (SHR). The SHR is the marriage of two basic elements of nanoplasmonics, a nanohole and a nanorod. A peak field intensity in the SHR occurs at the single tip of the nanorod inside the nanohole. The peak field is much stronger than those of the nanorod and nanohole, because the SHR field involves contributions from the following two field-enhancement mechanisms: (1) the excitation of surface plasmon resonances and (2) the lightning-rod effect. Here, we demonstrate the use of the SHR as a highly efficient nonlinear optical element for: (i) the generation of the third harmonic from a single SHR; (ii) the excitation of intense multiphoton luminescence from a single SHR.

Nanolithography based on an atom pinhole camera

In modern experimental physics the pinhole camera is used when the creation of a focusing element (lens) is difficult. We have experimentally realized a method of image construction in atom optics, based on the idea of an optical pinhole camera. With the use of an atom pinhole camera we have built an array of identical arbitrary-shaped atomic nanostructures with the minimum size of an individual nanostructure element down to 30 nm on an Si surface. The possibility of 30 nm lithography by means of atoms, molecules and clusters has been shown.

Single nanohole and photonic crystal: wavelength selective enhanced transmission of light

For the first time we have demonstrated an approach to control transmission of light through a single nanohole with the use of photon crystal microcavity. By use of the approach 28-fold enhanced transmission of light through a single nanohole in Au film has been experimentally demonstrated. The approach has the following advantages: (1) it enables to considerably increase transmission of light through a single nanohole, (2) the increase in transmission is unaffected by the hole diameter, (3) the transmission of nanohole is selective in frequency, the width of the resonance ~λ/90, (4) no auxiliary structures are necessary on the surface of the Au film (extra nanoholes, grooves, etc.).

Single nanohole and photoluminescence: nanolocalized and wavelength tunable light source

We are first to demonstrate a broadband, nanometer-scale, and background-free light source that is based on photoluminescence of a single nanohole in an Au film. We show that a nanohole with a diameter of as small as 20 nm in a 200-nm thick Au film can be used for this purpose. Further development of the localized source that involves the use of a photon-crystal microcavity with a Q-factor of 100 makes it possible to create a 30-fold enhanced, narrowband tunable light source and with a narrow directivity of the radiation.

Split hole resonator: A nanoscale UV light source

Due to a strong light absorption by metals, it is believed that plasmonic nanostructures cannot be used for generating intensive radiation harmonics in the UV spectral range. We present results of investigation of the nonlinear optical interaction of laser radiation with a single gold nanostructure in the geometry of the Split-Hole Resonator (SHR) [1, 2] under the-state-of-the-art experimental realized conditions: (1) the laser pulse duration is ultimately short (two cycles of the laser pulse wave) to maximally reduce the thermal effects on the nanostructure; (2) the laser light intensity is ultimately high and close to the air ionization threshold; (3) the geometry of the nanostructure is optimal ensuring a record-high efficiency of the nonlinear optical interaction; and (4) the SHR nanostructure is formed in a single crystal gold nanofilm that is flat on the atomic level. Several multipole plasmon resonances can simultaneously be excited in the SHR nanostructure. A strong nonlinear optical interaction at the frequencies of these resonances that leads to (i) the second-harmonic generation, (ii) the third harmonic generation (THG), and (iii) the light generation at mixed frequencies. The THG near field amplitude reaches 0.6% of the fundamental frequency field amplitude, which enables the creation of UV radiation sources with a record high intensity. The UV light may find many important applications including biomedical ones (such as cancer therapy).

Extremely high transmission of light through a nanohole inside a photonic crystal

The transmission of light through single nanoholes with diameters considerably smaller than the wavelength of light (smaller than λ/10) is experimentally studied. The nanoholes were made in a gold film, which is a part of a photonic crystal forming a microcavity with the quality factor Q ≈ 100. A 28-fold increase in the transmission of light through a nanohole inside the microcavity compared to transmission through a nanohole in a gold film is demonstrated. The high spectral selectivity of light transmission through a nanohole is discovered, which is characterized by two features: (i) the transmission maximum is located at the resonance wavelength of the microcavity and (ii) the peak full width at half-maximum is about λ/90.

Laser-induced quantum adsorption of atoms on a surface

A method of the quantum adsorption of atoms on a surface is proposed and experimentally implemented. The loading of atoms into a surface potential well (adsorption) occurs due to the loss of kinetic energy in the process of the inelastic collision of two laser-excited atoms. This scheme is implemented for Rb atoms adsorbed on the surface of a YAG crystal. The possibility of producing microstructures of arbitrary shape that consist of atoms localized on the dielectric surface is also demonstrated.

Giant enhancement of two photon induced luminescence in metal nanostructure.

We experimentally demonstrate a drastic increase in the rate of radiative process of a nanoscale physical system with implementation of the three physical effects: (1) the size effect, (2) plasmon resonance and (3) the optical Tamm state. As an example of a nanoscale physical system, we choose a single nanohole in Au film when the nanohole is embedded in a photonic crystal of a specific type that maintains an optical Tamm state and as a radiative process - a nonlinear photoluminescence. The efficiency of the nonlinear photoluminescence is increased by more than 10(7) times in compare to a bulk material.

Nanoscale and femtosecond optical autocorrelator based on a single plasmonic nanostructure

We demonstrated a nanoscale size, ultrafast and multiorder optical autocorrelator with a single plasmonic nanostructure for measuring the spatio-temporal dynamics of femtosecond laser light. As a nanostructure, we use a split hole resonator (SHR), which was made in an aluminium nanofilm. The Al material yields the fastest response time (100?as). The SHR nanostructure ensures a high nonlinear optical efficiency of the interaction with laser radiation, which leads to (1) the second, (2) the third harmonics generation and (3) the multiphoton luminescence, which, in turn, are used to perform multi-order autocorrelation measurements. The nano-sized SHR makes it possible to conduct autocorrelation measurements (i) with a subwavelength spatial resolution and (ii) with no significant influence on the duration of the laser pulse. The time response realized by the SHR nanostructure is about 10?fs.

Focusing of an atomic beam by a two-dimensional magneto-optical trap

A method for focusing neutral atoms based on the light-pressure force in a nonuniform magnetic field is proposed and analyzed. Its particular scheme is realized by means of a two-dimensional magneto-optical trap using a thermal beam of Rb atoms. A feature of this focusing method is the linear dependence of the focal length on the longitudinal velocity of atoms in contrast to the quadratic dependence in the known methods of focusing material-particle beams. The minimum size of the waist of the focused atomic beam is equal to 270 µm. Owing to focusing by means of the two-dimensional magneto-optical trap, the velocity monochromatization of a thermal atomic beam is realized: the width of the distribution of the longitudinal atomic velocities in the beam is reduced from 350 to 60 m/s.