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The Drexhage's experiment for sound
No full textDrexhage’s seminal observation that spontaneous emission rates of fluorophores vary with distance from a mirror uncovered the fundamental notion that a source’s environment determines radiative linewidths and shifts. Further, this observation established a powerful tool to determine fluorescence quantum yields. We present the direct analogue for sound. We demonstrate that a Chinese gong at a hard wall experiences radiative corrections to linewidth and line shift, and extract its intrinsic radiation efficiency. Beyond acoustics, our experiment opens new ideas to extend the Drexhage experiment to metamaterials, nanoantennas, and multipolar transitions
Soliton dynamics in semiconductor photonic crystals
Get PDFSemiconductor optical waveguides have been the subject of intense study as both fundamental objects of study, as well as a path to photonic integration. In this talk I will focus on the nonlinear evolution of optical solitons in photonic crystal waveguides made of semiconductor materials. The ability to independently tune the dispersion and the nonlinearity in photonic crystal waveguides enables the examination of completely different nonlinear regimes in the same platform. I will describe experimental efforts utilizing time-resolved measurements to reveal a number of physical phenomena unique to solitons in a free carrier medium. The experiments are supported by analytic and numerical models providing a deeper insight into the physical scaling of these processes. © (2016) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only
Thermodynamic theory of the plasmoelectric effect
Get PDFResonant metal nanostructures exhibit an optically induced electrostatic potential when illuminated with monochromatic light under off-resonant conditions. This plasmoelectric effect is thermodynamically driven by the increase in entropy that occurs when the plasmonic structure aligns its resonant absorption spectrum with incident illumination by varying charge density. As a result, the elevated steady-state temperature of the nanostructure induced by plasmonic absorption is further increased by a small amount. Here, we study in detail the thermodynamic theory underlying the plasmoelectric effect by analyzing a simplified model system consisting of a single silver nanoparticle. We find that surface potentials as large as 473 mV are induced under 100 W/m(2) monochromatic illumination, as a result of a 11 mK increases in the steady-state temperature of the nanoparticle. Furthermore, we discuss the applicability of this analysis for realistic experimental geometries, and show that this effect is generic for optical structures in which the resonance is linked to the charge density
Imaging of electric and magnetic fields near plasmonic nanowires
Get PDFNear-field imaging is a powerful tool to investigate the complex structure of light at the nanoscale. Recent advances in near-field imaging have indicated the possibility for the complete reconstruction of both electric and magnetic components of the evanescent field. Here we study the electro-magnetic field structure of surface plasmon polariton waves propagating along subwavelength gold nanowires by performing phase- and polarization-resolved near-field microscopy in collection mode. By applying the optical reciprocity theorem, we describe the signal collected by the probe as an overlap integral of the nanowire’s evanescent field and the probe’s response function. As a result, we find that the probe’s sensitivity to the magnetic field is approximately equal to its sensitivity to the electric field. Through rigorous modeling of the nanowire mode as well as the aperture probe response function, we obtain a good agreement between experimentally measured signals and a numerical model. Our findings provide a better understanding of aperture-based near-field imaging of the nanoscopic plasmonic and photonic structures and are helpful for the interpretation of future near-field experiments
Full vectorial mapping of the complex electric near-fields of THz resonators
Get PDFUsing micro-structured photo-conducting probes, we demonstrate full vectorial mapping of the complex electric fields in the near-field region of a resonant structure at THz frequencies. The investigated structure represents the simplest case of a resonator: a metallic rod. We show field amplitude as well as phase maps for the three field components at the half wavelength (λ/2) resonance of the rod. The field as well as the phase distributions are in excellent agreement with our physical understanding of local electric-field distributions in the vicinity of λ/2 resonant structures and are validated by numerical simulations. These measurements can be a platform for performance optimization of the emerging field of THz photonic and plasmonic devices with complex sub-wavelength structures
Femtosecond plasmon and photon wave packets excited by a high-energy electron on a metal or dielectric surface
Get PDFSwift electrons generate coherent transition radiation (TR) when crossing a material surface, as well as surface plasmon polaritons (SPPs) when the material is metallic. We present analytical and numerical calculations that describe the time- and space-dependent electric fields of TR and SPPs induced by 30–300 keV electrons on a Drude metal surface. The generated SPPs form wave packets a few-hundred femtoseconds in duration, depending on the material permittivity. High-frequency components close to the plasmon resonance are strongly damped,
causing the wave packets to shift to lower frequencies as they propagate further. TR is emitted to the far field as ultrashort wave packets consisting of just a few optical cycles, with an intensity and angle dependence that is determined by the material permittivity. The excitation reaches its peak amplitude within a few femtoseconds and then drops off strongly for longer times. From a correlation between material permittivity and the calculated emission behavior, we determine qualitative predictions of the TR evolution for any given material. The results presented here provide key insights into the mechanisms enabling swift electrons to serve as nanoscale optical
excitation sources
Impact of local-field effects on the plasmonic enhancement of vibrational signals by infrared nanoantennas
Get PDFWe have developed an analytical model that provides a mechanistic description of the plasmonic enhancement of vibrational signals by infrared nanoantennas. Our treatment is based on a coupled-point-dipole model which considers the interaction between a point-like nanoantenna and a single vibrational dipole moment. This idealized model is refined in two consecutive steps. The first step generalizes the model to make the treatment of non-point-like nanoantennas possible. The second step deals with local-field effects originating from the mutual interaction of the molecular vibrations. We have compared the results of our model with finite-difference time-domain simulations, and we find that our model predicts both the lineshapes and the amplitudes of the vibrational signals in a quantitative manner. Our analysis shows that the local-field effects play a surprisingly dominant role in the plasmonic enhancement, and we discuss possibilities of engineering this local field in order to further boost the plasmonic amplification
Planar metal/dielectric single-periodic multilayer ultraviolet flat lens
Get PDFIn 1968, Veselago predicted that a thin film composed of a material with a negative refractive index would act as a flat lens [Sov. Phys. Usp. 10, 509 (1968)]. Hyperbolic metamaterials have been designed that show negative refraction, but the condition of an isotropic refractive index =−1 required to realize a diffraction-limited focus cannot be realized using the hyperbolic dispersion. Here, we present an experimental realization of a metamaterial design in which the dispersion is described by spherical rather than hyperbolic isofrequency wavevector contours, emulating an isotropic refractive index =−1. We fabricate a flat lens that operates in the UV at =364 nm using a silver/titanium dioxide single-periodic thin-film multilayer structure. Using confocal microscopy, we find a clear focus positioned only 350 nm away from the flat lens surface, in very good agreement with analytical calculations and numerical simulations