Философия и интеллект

We use symmetry considerations to understand and unravel near-field measurements, ultimately showing that we can spatially map three distinct fields using only two detectors. As an example, we create 2D field maps of the outof- plane magnetic field and two in-plane fields for a silicon ridge waveguide. Furthermore, we are able to identify and remove polarization mixing of less than 1?30 of our experimental signals. Since symmetries are prevalent in nanophotonic structures and their near-fields, our method can have an impact on many future near-field measurements

Nanoscale electric and magnetic optical vector fields: mapping & injection

Nanophotonic structures, which offer a sub-wavelength control over light and nearby emitters, promise to advance, for example, our ability to harvest light, process information and detect (bio-) chemical compounds. In general, the optical field distributions near nanophotonic structures are much more complex than those in the far field. That is, nanophotonic structures achieve much of their unique functionalities because both the electromagnetic fields and the emission modification of nearby emitters spatially vary on the nanoscale with respect to their orientation, amplitude and phase. Furthermore, unlike for conventional microscopic structures, the interaction between the optical magnetic fields and nanophotonics structures frequently plays an important role. Hence, an understanding of light-matter interactions at the nanoscale requires a method to spatially map nanoscale electric and magnetic optical vector fields and the emission modification of electric and magnetic dipole emitters. \ud This thesis demonstrates that an aperture type near-field microscope can be used to achieve such a mapping. Firstly, we use the microscope to map the electric and magnetic optical fields of the photonic mode in a benchmark structure, a photonic crystal waveguide. Then, in both the electric and magnetic optical fields we identify points where a property of the field is undefined; optical singularities. For example, we identify polarization singularities, where the light is circularly polarized and the local orientation of the local polarization ellipse is undefined. We measure the local helicity of the circularly polarized light and we trace the position of the singularities in three-dimensional space. \ud Finally, we use the near-field microscope to mimic the emission modification of dipolar emitters and circularly polarized dipoles in particular. We show that the handedness of electric and magnetic circular dipoles, in combination with the local helicity of the photonic mode, can determine the direction of the light emitted into the waveguide. Additionally, we demonstrate that the optical wavelength can be used to tune the positions of efficient helicity-to-path coupling

Colloidal-Quantum-Dot Ring Lasers with Active Color Control

ISSN:1530-6984ISSN:1530-699

Two-Dimensional Drexhage Experiment for Electric- and Magnetic-Dipole Sources on Plasmonic Interfaces

ISSN:0031-9007ISSN:1079-711

Supplement 1: Tracking nanoscale electric and magnetic singularities through three-dimensional space

Originally published in Optica on 20 June 2015 (optica-2-6-540

Active Mode Switching in Plasmonic Microlasers by Spatial Control of Optical Gain

The pursuit of miniaturized optical sources for on-chip applications has led to the development of surface plasmon polariton lasers (plasmonic lasers). While applications in spectroscopy and information technology would greatly benefit from the facile and active tuning of the output wavelength from such devices, this topic remains underexplored. Here, we demonstrate optically controlled switching between predefined wavelengths within a plasmonic microlaser. After fabricating Fabry-Pérot plasmonic cavities that consist of two curved block reflectors on an ultrasmooth flat Ag surface, we deposit a thin film of CdSe/CdxZn1-xS/ZnS colloidal core/shell/shell nanoplatelets (NPLs) as the gain medium. Our cavity geometry allows the spatial and energetic separation of transverse modes. By spatially modulating the gain profile within this device, we demonstrate active selection and switching between four transverse modes within a single plasmonic laser. The fast buildup and decay of the plasmonic modes promises picosecond switching times, given sufficiently rapid changes in the structured illumination.ISSN:1530-6984ISSN:1530-699

Single-Pulse Measurement of Orbital Angular Momentum Generated by Microring Lasers

Optical beams with helical phase fronts carry orbital angular momentum (OAM). To exploit this property in integrated photonics, micrometer-scale devices that generate beams with well-defined OAM are needed. Consequently, lasers based on microring resonators decorated with azimuthal grating elements have been investigated. However, future development of such devices requires better methods to determine their OAM, as current approaches are challenging to implement and interpret. If a simple and more sensitive technique were available, OAM microring lasers could be better understood and further improved. In particular, despite most devices being pulsed, their OAM output has been assumed to be constant. OAM fluctuations, which are detrimental for applications, need to be quantified. Here, we fabricate quantum-dot microring lasers and demonstrate a simple measurement method that can straightforwardly determine the magnitude and sign of the OAM down to the level of individual laser pulses. We exploit a Fourier microscope with a cylindrical lens and then investigate three types of microring lasers: with circular symmetry, with “blazed” grating elements, and with unidirectional rotational modes. Our results confirm that previous measurement techniques obscured key details about the OAM generation. For example, while time-averaged OAM from our unidirectional laser is very similar to our blazed grating device, single-pulse measurements show that detrimental effects of mode competition are almost entirely suppressed in the former. Nevertheless, even in this case, the OAM output exhibits shot-to-shot fluctuations. Thus, our approach reveals important details in the underlying device operation that can aid in the improvement of micrometer-scale sources with pure OAM output.ISSN:1936-0851ISSN:1936-086

Room-Temperature Strong Coupling of CdSe Nanoplatelets and Plasmonic Hole Arrays

ISSN:1530-6984ISSN:1530-699

Room-Temperature Strong Coupling of CdSe Nanoplatelets and Plasmonic Hole Arrays

Exciton polaritons are hybrid light-matter quasiparticles that can serve as coherent light sources. Motivated by applications, room-temperature realization of polaritons requires narrow, excitonic transitions with large transition dipoles. Such transitions must then be strongly coupled to an electromagnetic mode confined in a small volume. While much work has explored polaritons in organic materials, semiconductor nanocrystals present an alternative excitonic system with enhanced photostability and spectral tunability. In particular, quasi-two-dimensional nanocrystals known as nanoplatelets (NPLs) exhibit intense, spectrally narrow excitonic transitions useful for polariton formation. Here, we place CdSe NPLs on silver hole arrays to demonstrate exciton-plasmon polaritons at room temperature. Angle-resolved reflection spectra reveal Rabi splittings up to 149 meV for the polariton states. We observe bright, polarized emission arising from the lowest polariton state. Furthermore, we assess the dependence of the Rabi splitting on the hole-array pitch and the number N of NPLs. While the pitch determines the in-plane momentum for which strong coupling is observed, it does not affect the size of the splitting. The Rabi splitting first increases with NPL film thickness before eventually saturating. Instead of the commonly used N dependence, we develop an analytical expression that includes the transverse confinement of the plasmon modes to describe the measured Rabi splitting as a function of NPL film thickness