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In this contribution we concentrate on two aspects of THz science related to surface and particle plasmons. Firstly, we report on the generation of THz pulses via irradiation of arrays of silver nanoparticles by femtosecond laser pulses. We propose that this effect arises from the emission of photoelectrons by multi-photon excitation and subsequent acceleration of these emitted electrons by ponderomotive forces associated with the optical fields of the plasmons in the metallic nanostructures. Secondly, we demonstrate that semiconductors supports strongly confined surface plasmons in the THz frequency range. We show that these SPs can be utilized to enhance the light-matter interaction with dielectric layers above the semiconductor surface, thereby allowing us to detect the presence of layers around one thousand times thinner than the free space wavelength of the THz light. We discuss the viability of using semiconductor SPs for the purposes of THz sensing and spectroscopy.

Results obtained from modeling the light out‐coupling efficiency of an organic light‐emitting diode (OLED) structure containing the recently developed first‐generation fac‐tris(2‐phenylpyridine) iridium‐cored dendrimer (Ir‐G1) as the emissive organic layer are reported. Comparison of the results obtained for this material with those of corresponding structures based upon small‐molecule and polymer emissive materials is made. The calculations of out‐coupling efficiency performed here take account of many factors, including the photoluminescence quantum yield (PLQY) of the emissive materials. Further, how each material system might perform with regard to out‐coupling efficiency when a range of possible PLQYs are considered is shown. The calculations show that the very high efficiency of dendrimer‐based OLEDs can be attributed primarily to their high PLQY.

We report the fabrication of optically pumped solid‐state polymer lasers based on the semiconducting polymer poly(9,9‐dioctylfluorene) (PFO) using resonator structures that offer one‐ and two‐dimensional distributed feedback. The lasers are readily fabricated by solution deposition of thin polymer films on top of suitable grating microstructures etched into fused silica substrates. The devices operate in the blue spectral region, are highly efficient (slope efficiencies as high as 7.8 % are demonstrated), and exhibit very low threshold energies for oscillation (0.8 nJ per pulse). The operating characteristics of the lasers are investigated in detail. The transverse mode profiles and divergence of the output beams are measured and correlated with the internal lasing modes and the feedback mechanism present in the resonators. Additionally, broadband tuning of the emission wavelength over a range of ∼ 40 nm is demonstrated by controlling the supported resonant frequency of the laser cavities.

We report measurements of photoluminescence from corrugated thin films of a light-emitting polymer. We find that emission into guided modes that would otherwise be trapped in the polymer may Bragg scatter off the corrugation to produce useful, far-field radiation. Analysis of the angle dependence of this far-field emission together with theoretical modeling enables us to establish the nature of the optical modes guided by the structure. We show that the dispersion of the modes supported by corrugated polymer films depends on the depth of modulation of the corrugation and find that if the periodic corrugation is strong enough photonic band gap effects may be induced. We also address the question of whether Bragg-scattering of the guided modes, including surface plasmon polariton modes, may increase the efficiency of the emission. We measure and compare the efficiency with which radiation is produced by planar and corrugated structures, finding the corrugated structures to be up to a factor of 2.6 more efficient. We indicate how our results may be used in the search for ways to improve the efficiency of devices based on light emitting thin films.

The concentration distributions of fluorescein and acridine orange, at a water/silica interface, are determined using the technique variable-angle time-resolved evanescent wave-induced fluorescence spectroscopy. It is demonstrated theoretically that the radiative fluorescence lifetime of a molecule is affected in only a minor way by the presence of a dielectric interface. Consequently, time-resolved evanescent wave-induced fluorescence spectroscopy is used to measure the variations in the fluorescence quantum yield caused by the pressence of the interface. Knowledge of these variations is then used to determine molecular concentration distributions. The concentration distribution of fluorescein is found to be uniform and homogeneous as a function of distance away from the hydrophilic silica surface. However, it is found that a water/silica interface has a definite affect on the concentration distribution of acridine orange. A “surface associated” acridine orange population distinguishable from “bulk” acridine orange is demonstrated by spectral and kinetic analysis of EWIF emission. This information is then used to create concentration profiles of both molecular populations.

The optical properties of a thin layer of dye deposited on a metallic grating are significantly altered by the coupling between the dye molecules and the surface-plasmon polariton (SPP) modes of the interface. We present experimental results demonstrating that energy gaps which prohibit the propagation of SPPs may be used to control the absorption properties of such molecules. We compare our data with theory, and we use numerical modelling to show how the effect of the gap on the absorption may be optimized by a suitable choice of the grating profile.

A review of fluorescence near interfaces is presented. Recent work that examines the role of photonic mode density in this process is surveyed and the underlying concepts discussed. The review includes an examination of the role of surface and waveguide modes, as well as non-radiative decay. The importance of textured surfaces in providing large changes in photonic mode density and in coupling non-radiative modes to radiation is highlighted. Indications are given for future areas of research and on how photonic mode density may influence optical processes other than fluorescence.

We examine the propagation of surface-plasmon polaritons on textured surfaces. Specifically, we look at how a grating surface produces a band gap in the propagation of this mode and how the band gap depends on the propagation direction of the mode. This naturally leads to a discussion of a surface profile suitable for blocking surface mode propagation in all directions. By using a diffractive-optics-based theoretical modeling approach we examine the requirements for such a surface. We then confirm these expectations experimentally by producing a surface exhibiting a band gap for surface-plasmon polariton modes in all directions in the energy range 1.91–2.00 eV.

The calibration procedure is described for a two-channel imaging radiometer on board the Heat Capacity Mapping Mission, a single sensor satellite in a near polar orbit. The Heat Capacity Mapping Radiometer measures radiation temperature and reflectivity with an instantaneous FOV of 600 m and a noise equivalent temperature of 0.4 K at 280 K in the thermal IR channel. Unexplained changes in the system during satellite launch were treated through comparison with surface/atmosphere data to force agreement. This necessitated an offset from the prelaunch calibration by 5.5 K. Later comparisons showed no difference. Possible explanations are described.

Structured illumination increases the spatial bandwidth of optical microscopes. We demonstrate bandwidth extension using a physical grating placed close to the sample. This comprises an array of elongated nanoparticles, whose localized surface plasmon resonance is polarization dependent. By arranging the particle orientation to vary with position the grating can be moved by changing the input polarization. A projected optical grating provides an additional independent mechanism for bandwidth extension. Experimental results showing bandwidth improvement in one direction are presented, and the measures necessary to extend the technique for routine imaging are discussed.

Significant improvements in the operation of Er^3+-doped silica fiber lasers operating at wavelengths between 1.5 and 1.6 μm are reported. The use of 980 nm as the pump wavelength provides an output that is limited mainly by the quantum efficiency of the lasing process. It is thus considerably more efficient than previous results using ~810-nm pumping, where excited-state absorption degrades the lasing performance. Operation at three discrete output wavelengths is observed and is accounted for by studying gain across the lasing bandwidth.

We report the generation of THz pulses from arrays of silver nanoparticles when irradiated by femtosecond laser pulses. We suggest that this effect arises from the emission of photoelectrons by multi-photon excitation and subsequent acceleration of these emitted electrons by ponderomotive forces associated with the optical fields of the plasmons in the metallic nanostructures.