Light-matter interaction

Visual of Light', An Experimental Study about Art and Science of Light is a practicebased study beginning with the researcher's self-interest of light, specifically on the existing of light in everyday life context. It is intended to reveal the visual form of light as in physical appearance. This study enhances knowledge and understanding relating to the interconnection of art and science of light. It was progressively developed along with self-experience and the experimentation, which video recording device, video editing software and hand recording materials were taken as major tools. The scientific knowledge of light such as physic, optical phenomenon and perceptual psychology was explored together with the particular uses of light in terms of art and design. They are varied from natural light in architecture, lighting in film, abstract cinema to light art. Consequently, the study has revealed a creative final outcome that is the self-reflective manifestation of motion images of light in a video format. The visual forms and characteristics of light are expressively composed in the aesthetic visual language. The process of the creative practice, its development and the result are precisely and critically described with the contribution of knowledge and self-reflective experience. Keywords: Light / Natural light / Architecture / Abstract cinema / Light art / Optical phenomenon / Video / Lighting in film iii

In circuit QED, protocols for quantum gates and readout of superconducting qubits often rely on the dispersive regime, reached when the qubit-photon detuning {\Delta} is large compared to their mutual coupling strength. For qubits including the Cooper-pair box and transmon, selection rules dramatically restrict the contributions to dispersive level shifts {\chi}. By contrast, without selection rules many virtual transitions contribute to {\chi} and can produce sizable dispersive shifts even at large detuning. We present theory for a generic multi-level qudit capacitively coupled to one or multiple harmonic modes, and give general expressions for the effective Hamiltonian in second and fourth order perturbation theory. Applying our results to the fluxonium system, we show that the absence of strong selection rules explains the surprisingly large dispersive shifts observed in experiments and also leads to the prediction of a two-photon vacuum Rabi splitting. Quantitative predictions from our theory are in good agreement with experimental data over a wide range of magnetic flux and reveal that fourth-order resonances are important for the phase modulation observed in fluxonium spectroscopy.

The interaction of several components in the strong coupling regime yielding multiple Rabi splittings opens up remarkable possibilities for studies of multimode hybridization and energy transfer, which is of considerable interest in both fundamental and applied science. Here we demonstrate that three different components, such as core–shell Au@Ag nanorods and J-aggregates of two different dyes, can be integrated into a single hybrid structure, which leads to strong collective exciton–plasmon coupling and double-mode Rabi splitting totaling 338 meV. We demonstrate strong coupling in these multicomponent plexitonic nanostructures by means of magnetic circular dichroism spectroscopy and demonstrate strong magneto-optical activity for the three hybridized states resulting from this coupling. The J-aggregates of two different nonmagnetic dyes interact with metal nanoparticles effectively, achieving magnetic properties due to the hybridization of electronic excitations in the three-component system.

After a brief introduction to the field of light-responsive materials, this paper provides a general theory for mod-eling the photomechanical response of a material, applies it to the two best-known mechanisms of photothermal heating and photoisomerization, and then describes an experimental procedure for quantitative measurements of the stress response. Several different materials are characterized to illustrate how the experiments and theory can be used to isolate the contributing mechanisms through both photomechanical measurements and auxiliary measurements of laser heating and thermal expansion. The efficiency and figure of merit of the photomechanical response are defined on several scales from the molecule to the bulk, and the photomorphon-the basic material element that determines the bulk response-is introduced. The photomorphon provides a conceptual model that can be expressed in terms of viscoelastic elements, such as springs in series and parallel with the photoactive molecule. The photomechanical response, figure of merit, and the deduced microscopic photomechanical properties are tabulated and proposals for new materials classes are made.

Remote control of the pH of the medium is an important task for many applications in chemistry, medicine, and biology. Remote control of the pH using light is an intelligent and cost-effective approach. The nanoscale plasmon−exciton (plexciton) light−matter coupling is a physical phenomenon that provokes strong changes in the optical properties of the original plasmon and exciton bands, resulting in a transparency dip in the initial plasmon spectrum and formation of two hybrid plexciton side bands separated by the Rabi splitting energy. The plexciton coupling strength is unaffected by the temperature and light irradiation stressors but strongly depends on the transition dipole moment of the exciton material. Here, we show that the optical parameters of the plexciton coupling can be controlled by varying the pH of the medium. To demonstrate this, we obtained resonant light−matter coupling between the plasmon band of silver nanoplates and the J-band of J-aggregates with a Rabi splitting energy of up to 450 meV and found that both the extinction dip and the splitting energy are strongly affected by variation of pH from 2.5 to 11. We explain this effect by a change in the structure of the J-aggregates and reduction of the J-band intensity, which is confirmed by numerical simulation.

Coupling two lasers of different intensities and wavelengths inside bulk matter, also known as EIT, has applications in slowing down light. EIT essentially transforms an opaque material to a given radiation into a transparent one, and can be applied in new optoelectronic devices, including quantum circuits, and in quantum computing. The main challenge in using this procedure comes from the difficulty in the coherent retrieval of the light signal squeezed inside the bulk matter after the EIT process ceases. We propose an alternative to the EIT mechanism in which we use the interaction between a weak probe laser beam reflected near the Brewster angle and a stronger coupling laser beam directed at normal incidence toward the same dielectric surface. As opposed to a classical EIT-type phenomenon, in our case (1) the dielectric is transparent to both incident lasers, and (2) the coupling between the two beams is realized on the dielectric surface, within one dipole layer in thickness. The signature of the coupling between the two lasers is indicated by (1) a shift in the value of the Brewster angle measured in the direction of the reflected probe beam toward a value associated to the electric permittivity of the dielectric in interaction with the stronger laser alone, and (2) an interference pattern near Brewster angle with several minima, which can be interpreted similarly as for light diffraction patterns. This result indicates that we can lock a laser beam on a dielectric surface.

A fundamental feature and a longstanding drawback of the quasi-normal modes (QNMs), which describe light interaction with (leaky) open systems like nanoparti-cles, lies in the lack of completeness of the QNMs representation and in the divergence of their field profile due to the complex eigenfrequency associated to the leaky behavior. In this article, the QNMs expansion is obtained taking into consideration the frequency dispersion and the causality principle. The derivation based on the complex analysis ensures the completeness of the QNMs expansion and prevents from any divergence of the field profile. The general derivation is tested in the case of a one-dimensional open resonator made of a homogeneous medium with frequency dispersion given by the Lorentz model. For a harmonic excitation, the result of the QNMs expansion perfectly matches the exact formula for the field distribution outside as well as inside the resonator.

The optical properties of cadmium telluride nanowires have been simulated using the Mie scattering coefficients. It is seen that the absorption efficiency shows multiple peaks along the spectrum due to leaky mode resonance. The nanowires showed strong polarization dependence in smaller radius. Higher angle of incidence showed a suppressing effect on lower valued peaks on absorption efficiency. Scattering efficiency showed peaks at visible spectrum from 30nm to 100nm. Transverse magnetic wave showed a more pronounced effect in scattering than transverse electric wave.

https://doi.org/10.25560/68710

Optical imaging, optical detection (e.g. biosensors), and opsin based neuromodulation (e.g. optogenetics) are the major techniques that have changed the practice of neuroscience. All these techniques use arc lamps, Light Emitting Diodes (LEDs) and lasers as conventional light sources. However, these light sources are not biocompatible and are excessively bulky, which limits their effectiveness as brain implants. Many improvements are necessary, such as the development of appropriate alternative light sources integrated with biological cells to ensure their compatibility with established techniques in biological laboratories. Organic Light Emitting Diodes (OLEDs) combine optical and electrical properties with known advantages of customized materials providing appropriate color tunability, lightness, and low-cost solution processing. In addition, mechanical flexibility combined with the high elastic modulus and biological inertness of carbon-based polymers and nanomaterials confer major advantages for use in non-conformal body cavities. These attractive and innovative qualities of OLEDs make them an alternative and better light source for organic neuro-optoelectronics - the optoelectronic aspect of bioelectronics. However, engineering optoelectronic devices for operation in liquid environments requires a comprehensive understanding of the consequences that may arise. This research is innovative in designing and engineering stable and biocompatible OLEDs for incorporation into living tissues. As a result, organic LEDs do not have to alter cell morphology and electrophysiological integrity/function. The principal challenge is ensuring they can operate in a highly saline and biologically active aqueous environment. Finding materials that are inherently stable in the environment in which they function is key to device optimization. The research will investigate the stability and biocompatibility of commonly used OLED materials. Key electrodes, indium, tin, oxide, gold, aluminum and silver are characterized to examine their suitability for an aqueous environment. Treating organic light emitting polymers with laminin has shown enhanced cell adhesion and biocompatibility. Prolonged immersion in cell culture medium highlights the importance of cross-linkable polymers maintaining electrical, optical and morphological properties. These properties are critical to device performance. Insulator materials play complementary and necessary roles at the interface of the OLED/bio environment – ensuring the protection of the device against oxidative or reductive processes. Insulators are critical for extending the lifetime of devices in aqueous operation. They must be encapsulated with hydrophobic polymers for protection against neuron damage from electrical stimulation. Following from the above it becomes possible to design both a highly biocompatible prototype OLED device, which is suitable for fluorescence microscopy, and patch-clamp technique for electrophysiological investigations. This would be based on opsin activation and would also include the investigation of critical design parameters for efficient OLED-opsin coupling stimulation. Additionally, OLED devices have been investigated for in vivo optical imaging of functional cortical architecture and dynamics. https://doi.org/10.25560/68710

Twisted light is light carrying orbital angular momentum. The profile of such a beam is a ring-like structure with a node at the beam axis, where a phase singularity exists. Due to the strong spatial inhomogeneity the mathematical description of twisted-light–matter interaction is non-trivial, in particular close to the phase singularity, where the commonly used dipole-moment approximation cannot be applied. In this paper we show that, if the handedness of circular polarization and the orbital angular momentum of the twisted-light beam have the same sign, a Hamiltonian similar to the dipole-moment approximation can be derived. However, if the signs differ, in general the magnetic parts of the light beam become of significant importance and an interaction Hamiltonian which only accounts for electric fields is inappropriate. We discuss the consequences of these findings for twisted-light excitation of a semiconductor nanostructures, e.g., a quantum dot, placed at the phase singularity.

Optically stimulated luminescence (OSL) and thermoluminescence (TL) from the metastable states in solids are widely used in luminescent phosphors, dosimetry, geochronology, and thermo- and photo-chronometry. OSL and TL result from a combination of three different processes (charge detrapping, transport, and recombination) and are, therefore, not ideal for characterizing the charge trapping states. Therefore, despite many decades of research, the OSL and TL kinetics and the associated defect systems remain poorly understood in natural minerals. Recently, a radio-photoluminescence (RPL) signal has been discovered in feldspar (K-Na-Ca aluminosilicates occupying > 50% of Earth's crust) which helps overcome this limitation. This site-selective signal termed infrared photoluminescence (IRPL) arises from radiative relaxation of the excited state of the main electron trapping center (principal trap).

In this study, IRPL excitation and emission spectroscopy at cryogenic temperatures reveals two distinct electron-trapping centers (i.e. two principal traps) in feldspar, and helps to determine their trap depths and the excited-state energies. The two trapping centers show the same electron capture cross-sections and the excited-state relaxation lifetimes, but different ground- and excited-state energies. Based on this peculiar combination of trap characteristics, we conclude that that the principal traps consist of the same defect residing at two different crystal sites. The differences in the energy levels of the two principal traps explain their distinct optical and thermal bleaching behavior.

The usage of semiconductor nanostructures is highly promising for boosting the energy conversion efficiency in photovoltaics technology, but still some of the underlying mechanisms are not well understood at the nanoscale length. Ge quantum dots (QDs) should have a larger absorption and a more efficient quantum confinement effect than Si ones, thus they are good candidate for third-generation solar cells. In this work, Ge QDs embedded in silica matrix have been synthesized through magnetron sputtering deposition and annealing up to 800°C. The thermal evolution of the QD size (2 to 10 nm) has been followed by transmission electron microscopy and X-ray diffraction techniques, evidencing an Ostwald ripening mechanism with a concomitant amorphous-crystalline transition. The optical absorption of Ge nanoclusters has been measured by spectrophotometry analyses, evidencing an optical bandgap of 1.6 eV, unexpectedly independent of the QDs size or of the solid phase (amorphous or crystalline). A simple modeling, based on the Tauc law, shows that the photon absorption has a much larger extent in smaller Ge QDs, being related to the surface extent rather than to the volume. These data are presented and discussed also considering the outcomes for application of Ge nanostructures in photovoltaics.