A short resonator dye laser pumped by a travelling wave N2-laser

A tunable dye laser is described, which is pumped by 300 ps pulses from a travelling wave N₂-laser. Due to the short resonator length pulses with only 50 ps duration are emitted.     

Surface enhanced Raman scattering arising from multipolar plasmon excitation

Visible and near infrared extinction spectra of gold nanorod regular arrays exhibit several bands assigned to high multipolar order plasmon resonances. These up to ninth order multipolar resonances generate surface enhanced Raman scattering spectra with typically 5 x 10(4) enhancement which is of similar magnitude as those obtained for dipolar excitations.     

Metal nanoparticle gratings: influence of dipolar particle interaction on the plasmon resonance

We probe the influence of grating effects on plasmon excitations in gold nanoparticles arranged in regular two-dimensional patterns. Samples produced by electron-beam lithography are investigated by femtosecond time-resolved and spectroscopic methods. We find a strong dependence of the plasmon lifetime and resonance wavelength on the grating constant.     

Fluorescence properties of dyes adsorbed to silver islands,investigated by picosecond techniques

The fluorescence properties of dye molecules (rhodamine 6G and erythrosin) adsorbed on pure glass surfaces and on silver islands films are investigated by cw and picosecond time-resolved methods. On pure glass surfaces we observe concentration quenching below a critical intermolecular distance (reduction of the fluorescence power per molecule as well as shortened and non-exponential fluorescence decay). On silver islands films the shortening in fluorescence lifetime is more drastic and is nearly independent of the intermolecular distance. This behavior suggests an electrodynamic interaction between dye monomers and plasmons in the metal particles, modified by a damping influence of dye dimers.     

Electromagnetic energy transport via linear chains of silver nanoparticles

We propose the idea of a subwavelength-sized light guide represented by a linear chain of spherical metal nanoparticles in which light is transmitted by electrodynamic interparticle coupling. The light-transport properties of this system are investigated by use of model calculations based on generalized Mie theory. Considering Ag particles of 50-nm diameter, we find optimum guiding conditions for an interparticle spacing of 25 nm, and a corresponding 1/e signal-damping length of 900 nm is evaluated. The proposed principle of optical energy transport may be useful for subwavelength transmission lines within integrated optics circuits and for near-field optical microscopy.     

PICOSECOND DYNAMICS OF THE EXCITED STATE RELAXATIONS IN PHYTOCHROME

Abstract— A comparative study of the picosecond kinetics of rye ( Secale cereale L.) phytochrome, its 39 and 23 kDa chromopeptides and deuterated rye phytochrome has been carried out. Evidence is presented that the fluorescence decay of Pr contains a very short lifetime component (14 ps) which has escaped detection in the fluorescence studies reported so far. Thus, the overall decay is well described by four exponential components, two rapid (14 and 44 ps) and two slower ones (157 and 690 ps). The fluorescence decays of deuterated Pr and of a 39 and 23 kDa chromopeptide of Pr also require the analysis in terms of four exponentials for a good fit. Some of the lifetime and amplitude values obtained differ significantly from the values estimated for Pr. In the chromopeptides, the two longer components have distinctly slower decays. For the two faster components the lifetimes remain approximately the same, but their relative amplitudes vary greatly. In deuterated Pr, the lifetimes are affected only slightly by deuteration. In contrast, the decay amplitudes are strikingly altered. Moreover, from a rate equation simulation modelling the observed fluorescence kinetics, it turns out that the yields for the various deactivation steps in the chromopeptides and in deuterated Pr reveal differences from the corresponding values in Pr. The implications of the results presented with respect to the influence of the protein moiety of Pr on the picosecond relaxation process are discussed.     

Performance of capillary columns for high-temperature gas chromatography

The developments in stationary-phase synthesis and capillary column technology have opened new perspectives in the analysis of high-molecular-weight compounds (600 daltons) and thermolabile organic compounds by high-temperature-high-resolution gas chromatography. This branch of high-resolution gas chromatography deals with analysis performed up to 390 degrees C oven temperature (with some applications going up to 420 degrees C and even a few applications to 450 degrees C maximum). The technique has been applied to many different fields of science (e.g., organic geochemistry, environmental chemistry, archeology, and natural product research). Apolar and medium-polar gum phases can now be operated at temperatures from 400 to 480 degrees C, but these higher temperatures are seldom used because of the thermostability of the material used to make the capillary tubing. This paper shows the performance of nine commercial high-temperature columns when used in routine applications.     

Surface plasmon polariton microscope with parabolic reflectors

We report the realization of a two-dimensional optical microscope for surface plasmons polaritons (SPPs) based on parabolic Bragg mirrors. These mirrors are built from lithographically fabricated gold nanostructures on gold thin films. We show by direct imaging by leakage radiation microscopy that the magnification power of the SPP microscope follows basic predictions of geometrical optics. Spatial resolution down to the value set by the diffraction limit is demonstrated.     

Multipolar surface plasmon peaks on gold nanotriangles

In this paper, we report on the observation of multipolar surface plasmon excitation in lithographically designed gold nanotriangles, investigated by means of far-field extinction microspectroscopy in the wavelength range of 400-1000 nm. Several bands are observed in the visible and near infrared regions when increasing the side length of the triangles. The assignment of these peaks to successive in-plane multipolar plasmon modes is supported by calculations using the discrete dipole approximation method. We show that the lowest three multipolar excitations are clearly resolved in the visible and near infrared range. These new spectral features could be very promising in nanooptics or for chemosensing and biosensing applications.