Yehiam Prior

Strong coupling between molecular excited states and surface plasmon modes of a slit array in a thin metal film

A recent study of the Seideman group with international collaborators, unravels a new and fascinating phenomenon in strongly coupled molecules-nanoconstruct systems, namely, the emergence of a new spectral mode associated with collective, plasmon-induced interaction among the molecules. Ongoing work explores applications of the unique properties of the discovered mode, ranging from solar energy conversion to plasmon-enhanced spectroscopies and sensing. Transmission spectra illustrating the emergence of a new, nondispersive mode. The inset gives the transmission vs the distance of the molecules from the plasmonic array.

Methods of laser spectroscopy

This book presents information on the following topics: the one-atom maser and cavity quantum electrodynamics; Rydberg atoms and radiation; investigation of nonthermal population distributions with femtosecond optical pulses; intra- and intermolecular energy transfer of large molecules in solution after picosecond excitation; new techniques of time-resolved infrared and Raman spectroscopy using ultrashort laser pulses; spectral linewidth of semiconductor lasers; the hydrogen atom in a new light; laser frequency division and stabilization; modified optical Bloch equations for solids; CARS spectroscopy of transient species; off resonant laser induced ring emission; UV laser ionization spectroscopy and ion photochemistry; laser spectroscopy of proton-transfer in microsolvent clusters; recent advances in intramolecular electronic energy transfer; and photoionization and dissociation of the H/sub 2/ molecule near the ionization threshold.

Vibrational polarization beats in femtosecond coherent anti-Stokes Raman spectroscopy: A signature of dissociative pump–dump–pump wave packet dynamics

Knopp et al. [J. Raman Spectrosc. 31, 51 (2000)] have recently used resonant femtosecond coherent anti-Stokes Raman spectroscopy (CARS) to prepare and probe highly excited vibrational wave packets on the ground electronic potential surface of molecular iodine. The experiment uses a sequence of three resonant femtosecond pulses with two independently variable time delays. The first two pulses act as a pump and dump sequence to create a predefined, highly excited wave packet on the ground electronic state, whose amplitude is optimized by selecting the proper pump–dump (Raman) frequency difference and varying the time delay. The third pulse promotes the pump–dump wave packet to an excited electronic state, resulting in subsequent coherent emission of light at the anti-Stokes frequency. This fully-resonant CARS signal, measured as a function of time delay between the second and third pulses, oscillates at a frequency characteristic of the pump–dump wave packet. Due to anharmonicity, this frequency is a sensit...

Study of morphological behavior of single diamond crystals

Isolated diamond crystals are grown by hot filament chemical vapor deposition (CVD) on Si-substrates without nucleation enhancement. We investigate the development of isolated diamond crystals under changing growth conditions. The growth parameter is determined from isolated diamond crystals and the same crystal is regrown several times and detected repeatedly by a scanning electron microscope. The change in morphology can be followed as the growth conditions are changing. Multiply twinned particles are also investigated and observed to change their morphology with the growth parameter α. The dependence of the idiomorphic shape on the growth parameter α is measured experimentally and compared with model calculations. It is shown that the basic determination of the morphology of a multiply twinned particle occurs at the early part of the nucleation phase.

Subwavelength nonlinear phase control and anomalous phase matching in plasmonic metasurfaces.

Metasurfaces, and in particular those containing plasmonic-based metallic elements, constitute an attractive set of materials with a potential for replacing standard bulky optical elements. In recent years, increasing attention has been focused on their nonlinear optical properties, particularly in the context of second and third harmonic generation and beam steering by phase gratings. Here, we harness the full phase control enabled by subwavelength plasmonic elements to demonstrate a unique metasurface phase matching that is required for efficient nonlinear processes. We discuss the difference between scattering by a grating and by subwavelength phase-gradient elements. We show that for such interfaces an anomalous phase-matching condition prevails, which is the nonlinear analogue of the generalized Snells law. The subwavelength phase control of optical nonlinearities paves the way for the design of ultrathin, flat nonlinear optical elements. We demonstrate nonlinear metasurface lenses, which act both as generators and as manipulators of the frequency-converted signal.

Controlling the sense of molecular rotation

We introduce a new scheme for controlling the sense of molecular rotation. By varying the polarization and the delay between two ultrashort laser pulses, we induce unidirectional molecular rotation, thereby forcing the molecules to rotate clockwise/counterclockwise under field-free conditions. We show that unidirectionally rotating molecules are confined to the plane defined by the two polarization vectors of the pulses, which leads to a permanent anisotropy in the molecular angular distribution. The latter may be useful for controlling collisional cross-sections and optical and kinetic processes in molecular gases. We discuss the application of this control scheme to individual components within a molecular mixture in a selective manner.

Studying vibrational wavepacket dynamics by measuring fluorescence interference fluctuations

The principle of coherence observation by interference noise [COIN, Kinrot et al., Phys. Rev. Lett. 75, 3822 (1995)] has been applied as a new approach to measuring wavepacket motion. In the COIN experiment pairs of phase-randomized femtosecond pulses with relative delay time τ prepare interference fluctuations in the excited state population, so the correlated noise of fluorescence intensity—the variance varF(τ)—directly mimics the dynamics of the propagating wavepacket. The scheme is demonstrated by measuring the vibrational coherence of wavepacket motion in the B-state of gaseous iodine. The COIN interferograms obtained recover propagation, recurrences and spreading as the typical signature of wavepackets. The COIN measurements were performed with precisely tuned excitation pulses which cover the bound part of the B-state surface up to the dissociative limit. In combination with preliminary numerical calculations, comparison has been made with results from previous phase-locked wavepacket interferometr...

Observing molecular spinning via the rotational Doppler effect

The rotational Doppler frequency shift is observed for a circularly polarized lightwave propagating through a gas of synchronously spinning molecules by using a linearly polarized pulsed laser beam to align diatomic molecules and a linearly polarized pulse to induce concerted unidirectional rotation.

Nonlinear metamaterials for holography

A hologram is an optical element storing phase and possibly amplitude information enabling the reconstruction of a three-dimensional image of an object by illumination and scattering of a coherent beam of light, and the image is generated at the same wavelength as the input laser beam. In recent years, it was shown that information can be stored in nanometric antennas giving rise to ultrathin components. Here we demonstrate nonlinear multilayer metamaterial holograms. A background free image is formed at a new frequency—the third harmonic of the illuminating beam. Using e-beam lithography of multilayer plasmonic nanoantennas, we fabricate polarization-sensitive nonlinear elements such as blazed gratings, lenses and other computer-generated holograms. These holograms are analysed and prospects for future device applications are discussed.

Floating Tip Nanolithography

We demonstrate noncontact, high quality surface modification of soft and hard materials with spatial resolution of approximately 20 nm. The nanowriting is based on the interaction between the surface and the tip of a standard atomic force microscope illuminated by a focused femtosecond laser beam and hovering (at ambient conditions) 1-4 nanometers above the surface without touching it. Field enhancement at the tip-sample gap or high tip temperature are identified as the causes of material ablation.