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Author: Yongbao Sun
Publisher:
ISBN:
Category :
Languages : en
Pages : 265
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Book Description
Coherent control has been at the heart of the study of physical chemistry. Great advancement has been achieved in the past few decades in coherent control of classical systems by using spatially and temporally shaped electromagnetic waves. In this dissertation, we extend the concept of coherent control to a purely quantum mechanical collective system, namely, microcavity exciton-polariton Bose-Einstein condensates. Microcavity exciton-polaritons, hereafter simply polaritons, are bosonic quasiparticles formed in a resonant semiconductor microcavity by coupling the excitonic polarizabilities in quantum wells to the transverse mode of the confined optical field in the cavity. The light-matter dual nature allows direct control of polaritons through either their excitonic or photonic components. By utilizing the fact that polariton-exciton and polariton-polariton interactions are repulsive, all-optical control of polaritons was realized. By shaping the intensity fronts of the optical beam incident on a microcavity, the potential landscape felt by polaritons can be easily tailored. This is the key ingredient of this dissertation work. The light-matter dual nature endows polaritons a very small effective mass that is one hundred million times less than that of a hydrogen atom, leading to the observation of quantum phenomena such as condensation, superfluidity and quantized vortices at temperatures ranging from tens of Kelvin up to room temperatures. However, debates persist over whether the observed phenomena can be related to Bose- Einstein condensation because polaritons are not in thermal equilibrium. By applying all-optical trapping to a high-quality microcavity structure, polaritons at both spatial and thermal equilibrium were achieved across a broad range of densities and bath temperatures, as evidenced by the observed equilibrium Bose-Einstein distributions. A phase diagram for Bose-Einstein condensation of polaritons was produced for the first time, which agrees with the predictions of basic quantum gas theory. The thermalization behavior depends crucially on the interactions among polaritons. By changing the underlying excitonic/photonic fractions in polaritons, the interaction strength of polaritons can be varied, leading to control between nonequilibrium and equilibrium behavior of the polariton gas. The interactions also play a crucial role in polaritonic device operations. However, an accurate measurement of the polariton-polariton interaction strength has been not possible because of the difficulty in separating polaritons and excitons that are created by the same optical excitation. After propagating to the center of a sufficiently large optically induced annular trap, polaritons were separated from the incoherent populations of free carriers and hot excitons. The polariton interaction strength was then extracted from energies measured as a function of the polariton density. The measured interaction strength was about two orders of magnitude larger than previous theoretical estimates, putting polaritons squarely into the strongly interacting regime. Optical control can also be utilized to directly manipulate polariton condensates. By tailoring the size and pumping intensity of the optical trap, polariton condensates can be switched among different high-order modes and the homogeneous condensate mode. The redistribution of spatial densities is accompanied by a superlinear increase in the emission intensity as a function of excitation power, implying that polariton condensates in this geometry could be exploited as a multistate switch. The parameters for reproducible switching between the high-order states in the optical trap have been measured experimentally, giving us a phase diagram for the mode switching. It will serve well to calibrate the implementation of an exciton-polaritonic multistate switch.
Author: Yongbao Sun
Publisher:
ISBN:
Category :
Languages : en
Pages : 265
Get Book Here
Book Description
Coherent control has been at the heart of the study of physical chemistry. Great advancement has been achieved in the past few decades in coherent control of classical systems by using spatially and temporally shaped electromagnetic waves. In this dissertation, we extend the concept of coherent control to a purely quantum mechanical collective system, namely, microcavity exciton-polariton Bose-Einstein condensates. Microcavity exciton-polaritons, hereafter simply polaritons, are bosonic quasiparticles formed in a resonant semiconductor microcavity by coupling the excitonic polarizabilities in quantum wells to the transverse mode of the confined optical field in the cavity. The light-matter dual nature allows direct control of polaritons through either their excitonic or photonic components. By utilizing the fact that polariton-exciton and polariton-polariton interactions are repulsive, all-optical control of polaritons was realized. By shaping the intensity fronts of the optical beam incident on a microcavity, the potential landscape felt by polaritons can be easily tailored. This is the key ingredient of this dissertation work. The light-matter dual nature endows polaritons a very small effective mass that is one hundred million times less than that of a hydrogen atom, leading to the observation of quantum phenomena such as condensation, superfluidity and quantized vortices at temperatures ranging from tens of Kelvin up to room temperatures. However, debates persist over whether the observed phenomena can be related to Bose- Einstein condensation because polaritons are not in thermal equilibrium. By applying all-optical trapping to a high-quality microcavity structure, polaritons at both spatial and thermal equilibrium were achieved across a broad range of densities and bath temperatures, as evidenced by the observed equilibrium Bose-Einstein distributions. A phase diagram for Bose-Einstein condensation of polaritons was produced for the first time, which agrees with the predictions of basic quantum gas theory. The thermalization behavior depends crucially on the interactions among polaritons. By changing the underlying excitonic/photonic fractions in polaritons, the interaction strength of polaritons can be varied, leading to control between nonequilibrium and equilibrium behavior of the polariton gas. The interactions also play a crucial role in polaritonic device operations. However, an accurate measurement of the polariton-polariton interaction strength has been not possible because of the difficulty in separating polaritons and excitons that are created by the same optical excitation. After propagating to the center of a sufficiently large optically induced annular trap, polaritons were separated from the incoherent populations of free carriers and hot excitons. The polariton interaction strength was then extracted from energies measured as a function of the polariton density. The measured interaction strength was about two orders of magnitude larger than previous theoretical estimates, putting polaritons squarely into the strongly interacting regime. Optical control can also be utilized to directly manipulate polariton condensates. By tailoring the size and pumping intensity of the optical trap, polariton condensates can be switched among different high-order modes and the homogeneous condensate mode. The redistribution of spatial densities is accompanied by a superlinear increase in the emission intensity as a function of excitation power, implying that polariton condensates in this geometry could be exploited as a multistate switch. The parameters for reproducible switching between the high-order states in the optical trap have been measured experimentally, giving us a phase diagram for the mode switching. It will serve well to calibrate the implementation of an exciton-polaritonic multistate switch.
Author: Georgios Roumpos
Publisher: Stanford University
ISBN:
Category :
Languages : en
Pages : 157
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Book Description
In a homogeneous two-dimensional system at non-zero temperature, although there can be no ordering of infinite range, an ordered superfluid phase is expected to occur for a Bose liquid. Theory predicts that, in this phase, the correlation function decays with distance as a power law, and quantum vortices are bound to antivortices to form molecular-like pairs. We study the relevance of this theory to microcavity exciton polaritons. These are two-dimensional bosonic quasiparticles formed as a superposition of a microcavity photon and a semiconductor quantum well exciton, and have been shown to condense at high enough densities. Because of the short lifetime, equilibrium is not established, but we instead probe the steady state of the system, in which particles are continuously injected from a pumping reservoir. We employ a Michelson interferometer setup to measure the first order spatial correlation function of such a condensate. The gaussian form of the short-distance decay allows us to define an effective thermal de Broglie wavelength, although the system is not in thermal equilibrium. The long-distance decay is measured to be a power law with an exponent in the range 0.9-1.2, larger than is possible in equilibrium. Our non-equilibrium theory suggests that this can be attributed to laser pumping noise. We also present our observation of a single vortex-antivortex pair in a condensate of the appropriate size. Pairs are generated due to pumping noise, and are formed sequentially at the same point due to the inhomogeneous pumping spot profile. They are revealed in the time-integrated phase maps acquired using Michelson interferometry. Our results suggest that vortex-antivortex pairs can be created in a two-dimensional condensate without rotation or stirring. The observed correlated motion of a vortex and antivortex imply that vortex-antivortex pairs do not dissociate, which is consistent with the measured power law decay of the spatial correlation function. These two experiments uniquely describe the condensate phase fluctuations and provide stringent tests to theories of nonequilibrium condensation. They also highlight the exciton polariton condensate as a very well characterized system showing mesoscopic coherence and deepen our understanding of fundamental two-dimensional bosonic physics. Progress in this field is expected to lead towards long-sought applications such as quantum simulation or low-threshold laser sources.
Author: Daniele Sanvitto
Publisher: Springer Science & Business Media
ISBN: 3642241867
Category : Science
Languages : en
Pages : 416
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Book Description
In the past decade, there has been a burst of new and fascinating physics associated to the unique properties of two-dimensional exciton polaritons, their recent demonstration of condensation under non-equilibrium conditions and all the related quantum phenomena, which have stimulated extensive research work. This monograph summarizes the current state of the art of research on exciton polaritons in microcavities: their interactions, fast dynamics, spin-dependent phenomena, temporal and spatial coherence, condensation under non-equilibrium conditions, related collective quantum phenomena and most advanced applications. The monograph is written by the most active authors who have strongly contributed to the advances in this area. It is of great interests to both physicists approaching this subject for the first time, as well as a wide audience of experts in other disciplines who want to be updated on this fast moving field.
Author: Yoseob Yoon
Publisher:
ISBN:
Category :
Languages : en
Pages : 271
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Book Description
Light-matter interactions are fundamental processes that allow us not only to interrogate material properties but also to coherently control material phases that cannot be reached otherwise. Matter-matter interactions, on the other hand, result in strong correlations and emergent behavior that cannot be explained in terms of single-particle physics. Exciton-polaritons (hereafter "polaritons") are hybrid quasiparticles in a semiconductor quantum-well microcavity that exhibit both light-matter and matter-matter interactions. Polaritons have the effective mass inherited from the ultralight cavity photon mass, which sets polariton transport phenomena to be photon-like and allows macroscopic quantum phenomena such as Bose-Einstein condensation and superfluidity up to room temperature. Meanwhile, the effect of photon dressing only reduces the exciton-exciton interaction strength by the Hopfield coefficient, which sets the polariton-polariton interaction strength to be exciton-like. Along with the narrow linewidth protected from inhomogeneously broadening, polaritons are an excellent platform to study interaction-induced physics and nonlinear device applications such as ultralow-power optical switches. In this thesis, we investigated the effects of light-matter and matter-matter interactions on various aspects of polaritons. In the first part, we first measured the polariton-polariton interaction strength by tracking the energy blueshift as a function of polariton density. This was enabled by separating and trapping polaritons away from a pumped region, where the measurement of polariton interactions can be obscured by much heavier particles such as a dark exciton reservoir. We provided possible mechanisms that explain the observed anomalously large blueshifts. In the second part, we addressed a long-standing debate on whether polaritons can reach thermal equilibrium. We used a long-lifetime microcavity structure to achieve Bose-Einstein distributions of polaritons, which was the first demonstration of polaritons in equilibrium. This allowed us to measure equilibrium properties, such as temperature and chemical potential, and to map out the phase diagram of Bose-Einstein condensation in a quasi-two-dimensional system. We further investigated how all-optical trapping and polariton interactions enhance relaxation and thermalization processes. In particular, we found that a significant redistribution of polaritons occurs through the reduced density of states and polariton interactions. In the third part, we studied trapped eigenstates and interference patterns of polariton condensates in various trapping and pump geometries. Competition between eigenstates and selection of one of them have been well explained by the overlap of real-space, monientum-space, and energy distributions between the pump and the eigenstate. A mismatch between the pump-induced potential profile and the polariton source profile was a key factor in determining the distribution of transported polaritons. In the last part, we extended the polariton physics to study topological and cooperative effects in open quantum systems. We demonstrated bulk Fermi arcs by connecting two exceptional points arising from the engineered non-Hermitian properties of a photonic crystal. In addition, we theoretically showed that a cascaded-cavity system can outperform a single-cavity system in terms of the single-photon indistinguishability and efficiency, which works even with bad quantum emitters and practical cavity quality factors. Our work provides invaluable insights into the fundamental light-matter and matter-matter interactions, as well as many-body physics of condensed matter and photonic systems.
Author: Sunipa Som
Publisher: Bentham Science Publishers
ISBN: 9815165410
Category : Science
Languages : en
Pages : 141
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Book Description
This reference book explains the fundamentals of Bose Einstein Condensation (BEC) in excitons and polaritons. It presents five chapters exploring fundamental concepts and recent developments on the subject. Starting with a historical overview of BEC, the book progresses into the origins and behaviors of excitons and polaritons. Chapters also cover the unique thermalization and relaxation kinetics of excitons, and the distinctive features of polaritons, such as lasing, superfluidity, and quantized vortices. The chapters dedicated to BEC in excitons and polaritons detail experimental techniques, theoretical modeling, recent advancements, and practical applications in a simplified way for beginners. This book serves as a resource for researchers, physicists, and students interested in the phenomena of BEC, providing insights into both the theoretical foundations and the practical implications of excitons and polaritons.
Author: Alexey Kavokin
Publisher: Elsevier
ISBN: 008048137X
Category : Technology & Engineering
Languages : en
Pages : 248
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Book Description
Volume 32 of the series addresses one of the most rapidly developing research fields in physics: microcavities. Microcavities form a base for fabrication of opto-electronic devices of XXI century, in particular polariton lasers based on a new physical principle with respect to conventional lasers proposed by Einstein in 1917. This book overviews a theory of all major phenomena linked microcavities and exciton-polaritons and is oriented to the reader having no background in solid state theory as well as to the advanced readers interested in theory of exciton-polaritons in microcavities. All major experimental discoveries in the field are addressed as well. · The book is oriented to a general reader and is easy to read for a non-specialist.· Contains an overview of the most essential effects in physics of microcavities experimentally observed and theoretically predicted during the recent decade such as:. · Bose-Einstein condensation at room temperature.· Lasers without inversion of population.· Microcavity boom: optics of the XXI century!· Frequently asked questions on microcavities and responses without formulas. · Half-light-half-matter quasi-particles: base for the future optoelectronic devices
Author: Pranai Vasudev
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Bose-Einstein condensation (BEC) is a remarkable manifestation of quantum mechani- cal behaviour where a macroscopic number of particles occupy a single particle ground state. Typical realizations of BEC occur at temperatures close to absolute zero. In this thesis, we propose a route towards full thermal equilibirum, room-temperature BEC of "half-light" - "half-matter" quasiparticles known as exciton-polaritons. Our proposed strategy uses three-dimensional photonic crystals to form the optical resonator; this leads to long lived confined optical modes. These long lived confined optical modes allow the condensates to reach full thermal equilibrium. Photonic crystal resonators ensure that the light-matter coupling strengths are significantly stronger than in conventional archi- tectures; this leads to BEC formation at higher temperatures. A central quantity in our work is the (lower) exciton-polariton dispersion depth. The dispersion depth is an energy scale that governs the limit on the critical temperature. Strategies for increasing the dispersion depth to facilitate room-temperature BEC will be discussed. We first examine exciton-polariton BEC in optical resonators composed of slanted pore photonic crystals. We consider InGaAs/InP quantum wells embedded in the res- onator to allow for light emission at a wavelength of approximately 1300 nm. In esti- mating the critical temperature, we ensure the use of modest exciton-polariton densities to avoid the saturation of the exciton resonance. Using three quantum wells, our study reveals that exciton-polariton BEC occurs for temperatures above 300 K and that our results are robust to both photonic and electronic disorder. Next, we investigate exciton-polariton BEC in optical resonators composed of wood- pile photonic crystals. We treat GaAs/AlAs quantum wells embedded in resonator to allow for the emission of light with a wavelength of approximately 750 nm. Due to the x-y symmetry of the woodpile photonic crystal, the exciton-polariton ground state exhibits a two-fold polarization degeneracy. We show that symmetry breaking lifts the degeneracy of the ground state and results in larger critical temperatures and higher condensate fractions, in comparison to a symmetrical woodpile structure. Our results show that for three quantum wells and a moderate exciton-polariton density that a BEC can be obtained at temperatures over 300 K; this condensate is robust to disorder.
Author: Qing Gu
Publisher: Cambridge University Press
ISBN: 1316982696
Category : Technology & Engineering
Languages : en
Pages : 333
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Book Description
This unique resource explains the fundamental physics of semiconductor nanolasers, and provides detailed insights into their design, fabrication, characterization, and applications. Topics covered range from the theoretical treatment of the underlying physics of nanoscale phenomena, such as temperature dependent quantum effects and active medium selection, to practical design aspects, including the multi-physics cavity design that extends beyond pure electromagnetic consideration, thermal management and performance optimization, and nanoscale device fabrication and characterization techniques. The authors also discuss technological applications of semiconductor nanolasers in areas such as photonic integrated circuits and sensing. Providing a comprehensive overview of the field, detailed design and analysis procedures, a thorough investigation of important applications, and insights into future trends, this is essential reading for graduate students, researchers, and professionals in optoelectronics, applied photonics, physics, nanotechnology, and materials science.
Author: Nick Proukakis
Publisher: World Scientific
ISBN: 1848168128
Category : Science
Languages : en
Pages : 579
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Book Description
This volume provides a broad overview of the principal theoretical techniques applied to non-equilibrium and finite temperature quantum gases. Covering Bose-Einstein condensates, degenerate Fermi gases, and the more recently realised exciton-polariton condensates, it fills a gap by linking between different methods with origins in condensed matter physics, quantum field theory, quantum optics, atomic physics, and statistical mechanics.
Author: Arash Rahimi-Iman
Publisher: Springer Nature
ISBN: 303039333X
Category : Science
Languages : en
Pages : 291
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Book Description
This book offers an overview of polariton Bose–Einstein condensation and the emerging field of polaritonics, providing insights into the necessary theoretical basics, technological aspects and experimental studies in this fascinating field of science. Following a summary of theoretical considerations, it guides readers through the rich physics of polariton systems, shedding light on the concept of the polariton laser, polariton microcavities, and the technical realization of optoelectronic devices with polaritonic emissions, before discussing the role of external fields used for the manipulation and control of exciton–polaritons. A glossary provides simplified summaries of the most frequently discussed topics, allowing readers to quickly familiarize themselves with the content. The book pursues an uncomplicated and intuitive approach to the topics covered, while also providing a brief outlook on current and future work. Its straightforward content will make it accessible to a broad readership, ranging from research fellows, lecturers and students to interested science and engineering professionals in the interdisciplinary domains of nanotechnology, photonics, materials sciences and quantum physics.
