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Quasi-Static Averaging of Microscopic Fields and the Concept of Bianisotropy
Published in Constantin Simovski, Composite Media with Weak Spatial Dispersion, 2018
It is worth to notice that in the literature on the light-matter interaction there is a physical effect referred to as the effect of WSD which has nothing to do with the content of this book. It is the effect of the so-called exciton-polariton interaction in semiconductors. In some meaning, photovoltaic semiconductors, actually, possess WSD resulting in nonzero values of κ1 and κ2 in Eq. (1.4). For composite and molecular media these terms origin from the retardation (inertia) in the electromagnetic response of a constitutive particle. The physics of these differential susceptibilities for a photovoltaic semiconductor is totally different.
Linear Optical Properties of Semiconductors
Published in Inamuddin, Mohd Imran Ahamed, Rajender Boddula, Tariq Altalhi, Optical Properties and Applications of Semiconductors, 2023
Muhammad Rizwan, Asma Ayub, Bakhtawer Razaq, Aleena Shoukat, Iqra Ilyas, Ambreen Usman
Strong coupling of exciton with the field of radiation in semiconductors for direct band-to-band transitions can lead to many modifications in optical properties. As a consequence, signatures of exciton in optical spectra get changed, which are to be discussed later. Mixed states of electromagnetic radiation and excitation give rise to exciton-polariton. In direct transition, the phenomenon of an electron-hole pair is generated by an incident photon. Exciton is formed by the Coulomb interaction among the holes and electrons. The vertical lines represent these excitons or the photon exchange among the electrons and holes (Haug and Koch 2009).
Bose-Einstein condensation of photons from the thermodynamic limit to small photon numbers
Published in Journal of Modern Optics, 2018
Robert A. Nyman, Benjamin T. Walker
There is a large community working with light and solid-state matter which are strongly-coupled, in the cavity QED sense that the coherent coupling is faster than incoherent mechanisms like spontaneous emission or cavity loss, using microcavities. Strongly coupled light-matter systems are known as polaritons. Typically the light interacts with a quasiparticle made of a bound electron and hole pair known as an exciton, making an exciton–polariton. In near-planar microcavities, sufficient pump power leads polariton condensation [10]. Condensation is considered distinct from lasing in that the excitons interact with each other substantially (see Ref. [11], p. 362), approaching thermal equilibrium, even if imperfectly. The excitons associated with the condensed polaritons can be free to move (Wannier excitons, typical of inorganic semiconductors [12]) or bound to individual sites (Frenkel excitons, typical of organic fluorescent solids [13,14]). By contrast, thermalization and BEC of photons as described above is performed in the weak-coupling limit, and with liquid-state matter.
Magnetic dipolar modes in magnon-polariton condensates
Published in Journal of Modern Optics, 2021
Polaritons are bosonic quasiparticles. In a case of exciton polaritons, one observes strong coupling of the exciton with the optical-cavity photon. The spectral response displays mode splittings when the quantum wells and the optical cavity are in resonance. A number of quantum-well resonances were shown experimentally. Classically, the effect can be seen as the normal-mode split of coupled oscillators, the excitons and the electromagnetic field of the microcavity. Quantum mechanically, this is the Rabi vacuum-field splitting of the quantum-well excitons. Due to Bose–Einstein condensation of exciton-polaritons in semiconductor optics, one observes spontaneous phase transitions to quantum condensed phases with superfluidity and vortex formation. A quantized vortex is considered as a topological defect with zero density at its core. Quantization of a vortex in a BEC originates from the single-valuedness of the macroscopic wave function, that is, a change in the phase along an arbitrary close path must be an integral multiple of . At the same time, the -rotation effects can be observed. There are the spinor exciton-polariton condensates with half-integer vortices. It is worth noting also that excitons, by virtue of being composite particles made of two fermions, obey bosonic statistics as long as their density is low enough such that they do not overlap. In a small quantum dot, the excitons behave as fermions: we cannot put more than one in the same state. In this limit, we perceive the fermionic nature of the constituents [9–14].
Optical gain and photo-bleaching of organic dyes, quantum dots, perovskite nanoplatelets and nanodiamonds
Published in Liquid Crystals, 2023
Mahendran Vellaichamy, Miha Škarabot, Igor Muševič
Exciton-polariton materials exhibit hybridisation of excitons with confined light modes [24] and are promising for the realisation of low threshold lasing due to their high-optical gain reported in the literature [25]. While organic semiconductors sustain polaritons at room temperature and have been extensively studied for room temperature polariton devices, there is little information on their performance in terms of photo-bleaching. In our studies we were using organic semiconductor Anthracene (Sigma-Aldrich), and organic semiconductor perovskite CsPbBr3 and CsPbI3 nanoparticles (Mesolight). In addition to organic exciton-polariton materials, we studied fluorescent silica nanobeads (hiQ nano) as inorganic polariton materials. We also measured optical gain and photo-bleaching on thin layers of inorganic semiconductor CdSe/CdS quantum rods (Sigma-Aldrich), CdSe/ZnS quantum dots (Sigma-Aldrich), Fluorescent NV nanodiamonds (Nitrogen vacancy >900 NV/particle, Sigma-Aldrich) and green fluorescent NVN nanodiamonds (Adámas Nano). Some of the material properties are summarised in Table 2. A known concentration of particles is dispersed in organic solvent (hexane/toluene/methanol). To ensure homogenous distribution of particles, each dispersion was ultrasonicated for 5 minutes. Thin films of dispersed materials are prepared by drop casting 20–30 μl of dispersions on glass surface to get nearly uniform dry film. In all cases, except for the NV nanodiamonds, the deposited and dried film showed characteristics of a crystalline layer, indicated by regular and straight defect lines across the film. Particle size and particle concentration are given in Table 2. NVN nanodiamonds were studied in water dispersion that was introduced in a 7 μm thick glass cell.