There has been increasing fundamental and practical interest in the properties of dielectric microspheres in recent years. High-Q structural resonances that occur when the round trip optical path is an integral number of wavelengths can be exploited for quantum measurement and the observation of cavity QED effects. The spherical microparticle is also an important component of the earth’s atmosphere, contributing both to visual displays and global change. In this paper, we describe theoretical and experimental applications of optical pulse techniques to the characterization of dielectric spheres.
{"title":"Time-Domain Measurements of Light Propagation in Dielectric Spheres","authors":"W. Whitten, R. Shaw, M. Barnes, J. Ramsey","doi":"10.1364/qo.1997.qthe.8","DOIUrl":"https://doi.org/10.1364/qo.1997.qthe.8","url":null,"abstract":"There has been increasing fundamental and practical interest in the properties of dielectric microspheres in recent years. High-Q structural resonances that occur when the round trip optical path is an integral number of wavelengths can be exploited for quantum measurement and the observation of cavity QED effects. The spherical microparticle is also an important component of the earth’s atmosphere, contributing both to visual displays and global change. In this paper, we describe theoretical and experimental applications of optical pulse techniques to the characterization of dielectric spheres.","PeriodicalId":44695,"journal":{"name":"Semiconductor Physics Quantum Electronics & Optoelectronics","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"1997-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81956338","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A number of optoelectronic device applications of quantum well semiconductors depend on the saturation of exciton absorption features. Studies of exciton saturation at room temperature have resolved exciton-exciton interactions on timescales less than 300fs, and two distinct mechanisms based on phase space filling (PSF) and Coulomb effects caused by free carriers on longer timescales. Nonequilibrium carrier distributions were originally employed to separate Pauli exclusion and long range Coulomb effects [1]. More recently, optically induced circular dichroism was used to identify PSF and Coulomb exchange contributions [2]. However, Coulomb contributions can arise from both screening and collisional broadening. In this work, we have extended the use of circularly polarised ultrashort pulses to distinguish the two related Coulomb effects of screening and broadening and in addition, compared the relative contributions of excitons and free carriers to Coulomb contributions.
{"title":"Coulomb Contributions to Exciton Saturation in Room Temperature GaAs-AlxGa1-xAs Multiple Quantum Wells","authors":"M. Holden, GT Kennedy, A. Miller","doi":"10.1364/qo.1997.qthd.3","DOIUrl":"https://doi.org/10.1364/qo.1997.qthd.3","url":null,"abstract":"A number of optoelectronic device applications of quantum well semiconductors depend on the saturation of exciton absorption features. Studies of exciton saturation at room temperature have resolved exciton-exciton interactions on timescales less than 300fs, and two distinct mechanisms based on phase space filling (PSF) and Coulomb effects caused by free carriers on longer timescales. Nonequilibrium carrier distributions were originally employed to separate Pauli exclusion and long range Coulomb effects [1]. More recently, optically induced circular dichroism was used to identify PSF and Coulomb exchange contributions [2]. However, Coulomb contributions can arise from both screening and collisional broadening. In this work, we have extended the use of circularly polarised ultrashort pulses to distinguish the two related Coulomb effects of screening and broadening and in addition, compared the relative contributions of excitons and free carriers to Coulomb contributions.","PeriodicalId":44695,"journal":{"name":"Semiconductor Physics Quantum Electronics & Optoelectronics","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"1997-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76856268","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Resonant nonlinearities in quantum well structures arise from exciton saturation and band-filling due to photogeneration of free carriers. Through the Kramers-Kronig’s relation, a corresponding change in refractive index occurs close to the bandgap energy where the absorption change occurs. The change in refractive index can effectively be used to produce optical switching in devices that can convert phase changes into intensity changes or directional switching1. Although the turn-on of carrier induced nonlinearities is effectively an instantaneous effect which follows the photon pulse, these photogenerated carriers tend to linger on well after the photon pulse has passed. The recovery time is usually governed by carrier relaxation times2,3 or carrier removal rates4. In this work, we demonstrate all-optical switching in a Y-junction device in which two control optical pulses are used for each switching event. The first control pulse flips the state of the switch while the second control pulse turns the switch back to its initial state. The switch dynamics is related to other carrier induced devices demonstrated by other independent researchers5,6.
{"title":"Picosecond Switching using Resonant Nonlinearities in a Quantum Well Device","authors":"P. LiKamWa, A. Kan’an","doi":"10.1364/qo.1997.qthe.1","DOIUrl":"https://doi.org/10.1364/qo.1997.qthe.1","url":null,"abstract":"Resonant nonlinearities in quantum well structures arise from exciton saturation and band-filling due to photogeneration of free carriers. Through the Kramers-Kronig’s relation, a corresponding change in refractive index occurs close to the bandgap energy where the absorption change occurs. The change in refractive index can effectively be used to produce optical switching in devices that can convert phase changes into intensity changes or directional switching1. Although the turn-on of carrier induced nonlinearities is effectively an instantaneous effect which follows the photon pulse, these photogenerated carriers tend to linger on well after the photon pulse has passed. The recovery time is usually governed by carrier relaxation times2,3 or carrier removal rates4. In this work, we demonstrate all-optical switching in a Y-junction device in which two control optical pulses are used for each switching event. The first control pulse flips the state of the switch while the second control pulse turns the switch back to its initial state. The switch dynamics is related to other carrier induced devices demonstrated by other independent researchers5,6.","PeriodicalId":44695,"journal":{"name":"Semiconductor Physics Quantum Electronics & Optoelectronics","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"1997-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72460008","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Microcavity lasers have been shown to be promising devices owing to their characteristics such as very low threshold current, large modulation bandwidth, noise properties, etc. [1, 2, 3].
{"title":"Microcavity Semiconductor Lasers: Parameter Evaluation and Performances","authors":"G. Bava, P. Debernardi","doi":"10.1364/qo.1997.qfb.3","DOIUrl":"https://doi.org/10.1364/qo.1997.qfb.3","url":null,"abstract":"Microcavity lasers have been shown to be promising devices owing to their characteristics such as very low threshold current, large modulation bandwidth, noise properties, etc. [1, 2, 3].","PeriodicalId":44695,"journal":{"name":"Semiconductor Physics Quantum Electronics & Optoelectronics","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"1997-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74744545","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
C. A. Smith, S. Risbud, J. Cooke, Howard W. H. Lee
Our study of ZnSe quantum dots is motivated by the inherent interest in quantum confined systems and by the potential for shorter wavelength laser operation enabled by blue-shifted quantum confined energy levels. The optical and electronic properties of these nanocrystals as a function of the fabrication process were investigated with various optical techniques including photoluminescence (PL) lifetimes, and absorption, PL , and excitation spectroscopy.
{"title":"Laser Annealing of Trap States in ZnSe Quantum Dots","authors":"C. A. Smith, S. Risbud, J. Cooke, Howard W. H. Lee","doi":"10.1364/qo.1997.qthe.10","DOIUrl":"https://doi.org/10.1364/qo.1997.qthe.10","url":null,"abstract":"Our study of ZnSe quantum dots is motivated by the inherent interest in quantum confined systems and by the potential for shorter wavelength laser operation enabled by blue-shifted quantum confined energy levels. The optical and electronic properties of these nanocrystals as a function of the fabrication process were investigated with various optical techniques including photoluminescence (PL) lifetimes, and absorption, PL , and excitation spectroscopy.","PeriodicalId":44695,"journal":{"name":"Semiconductor Physics Quantum Electronics & Optoelectronics","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"1997-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88591061","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
C. Gmachl, J. Faist, F. Capasso, C. Sirtori, D. Sivco, A. Cho
Low threshold, single-mode quantum cascade whispering gallery lasers with emission wavelengths from 5.0 to 11.5 micrometer are reported. Their potential for true microcavities is discussed.
{"title":"Quantum Cascade Whispering Gallery Lasers","authors":"C. Gmachl, J. Faist, F. Capasso, C. Sirtori, D. Sivco, A. Cho","doi":"10.1364/qo.1997.qfa.1","DOIUrl":"https://doi.org/10.1364/qo.1997.qfa.1","url":null,"abstract":"Low threshold, single-mode quantum cascade whispering gallery lasers with emission wavelengths from 5.0 to 11.5 micrometer are reported. Their potential for true microcavities is discussed.","PeriodicalId":44695,"journal":{"name":"Semiconductor Physics Quantum Electronics & Optoelectronics","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"1997-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83085726","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
T. Fukuzawa, S. Y. Kim, T. Gustafson, E. Haller, E. Yamada
Two-dimensional (2D) bosons can undergo a Kosterlitz-Thouless transition[1], which does not involve macroscopic occupation of a single quantum state, but which can still result in superfluidity. In addition, strongly interacting bosons subject to a random potential can also exhibit superfluidity, as in the case of charged superfluidity that occurs in high-T c superconductors. Competition between the strength of the interaction and the degree of potential disorder are among the many complicated and competing factors which determine whether superfluidity is promoted or supressed in a Bose system[2]. Strong potential disorder forces bosons to localize and can result in an insulating Bose glass phase. Alternatively, repulsive interactions among bosons act to release them from their traps, to keep their inter-particle distances as uniform as the potential allows, and to arrange the flow direction. An appropriate interaction strength can thus promote superfluidity.
{"title":"Anomalous Diffusion of Repulsive Bosons in a Two-Dimensional Random Potential","authors":"T. Fukuzawa, S. Y. Kim, T. Gustafson, E. Haller, E. Yamada","doi":"10.1364/qo.1997.qthb.2","DOIUrl":"https://doi.org/10.1364/qo.1997.qthb.2","url":null,"abstract":"Two-dimensional (2D) bosons can undergo a Kosterlitz-Thouless transition[1], which does not involve macroscopic occupation of a single quantum state, but which can still result in superfluidity. In addition, strongly interacting bosons subject to a random potential can also exhibit superfluidity, as in the case of charged superfluidity that occurs in high-T c superconductors. Competition between the strength of the interaction and the degree of potential disorder are among the many complicated and competing factors which determine whether superfluidity is promoted or supressed in a Bose system[2]. Strong potential disorder forces bosons to localize and can result in an insulating Bose glass phase. Alternatively, repulsive interactions among bosons act to release them from their traps, to keep their inter-particle distances as uniform as the potential allows, and to arrange the flow direction. An appropriate interaction strength can thus promote superfluidity.","PeriodicalId":44695,"journal":{"name":"Semiconductor Physics Quantum Electronics & Optoelectronics","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"1997-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78378086","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Nowadays, due to the advances in nanolithography technology it is possible to fabricate structures whose electronic properties correspond to that of a quasi-one-dimensional electron gas. Such structures allow us to observe ballistic quantum transport at low temperatures, and remarkable experimental observations have resulted1. Many theoretical studies have investigated conductance fluctuations2 and voltage controlled defects. Cahay et al3 studied the problem of localization associated with the conductance fluctuations of an array of elastic scatterers. Joe et al4 discussed the effects of a voltage controlled impurity for the conductance of a single open quantum box. As the impurity size is changed, it causes conductance oscillations due to the interference of circulating and bound states of the quantum box. In this paper we analyze how changes in geometry of a structure with three open dots affect its electronic properties.
{"title":"Quantum Devices Using Multi-Dots Structures","authors":"E. Fagotto, S. Rossi, E. Moschim","doi":"10.1364/qo.1997.qthe.2","DOIUrl":"https://doi.org/10.1364/qo.1997.qthe.2","url":null,"abstract":"Nowadays, due to the advances in nanolithography technology it is possible to fabricate structures whose electronic properties correspond to that of a quasi-one-dimensional electron gas. Such structures allow us to observe ballistic quantum transport at low temperatures, and remarkable experimental observations have resulted1. Many theoretical studies have investigated conductance fluctuations2 and voltage controlled defects. Cahay et al3 studied the problem of localization associated with the conductance fluctuations of an array of elastic scatterers. Joe et al4 discussed the effects of a voltage controlled impurity for the conductance of a single open quantum box. As the impurity size is changed, it causes conductance oscillations due to the interference of circulating and bound states of the quantum box. In this paper we analyze how changes in geometry of a structure with three open dots affect its electronic properties.","PeriodicalId":44695,"journal":{"name":"Semiconductor Physics Quantum Electronics & Optoelectronics","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"1997-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88655141","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
R. Tyan, P. Sun, A. Salvekar, H. Chou, Chuan-cheng Cheng, F. Xu, A. Scherer, Y. Fainman
Subwavelength multilayer binary gratings (SMBG) can be seen as a 2-D periodic structures (see Fig.1a) with two periodic directions along the grating vector and the multilayer cascading direction. Such structures combine strong form- birefringence1,2 of the subwavelength grating with high reflectivity due the multilayer structure allowing us to design polarization sensitive microdevices, such as polarization selective mirror and polarizing beam splitter. Recently3 we introduce a new polarizing beam splitter (PBS) microdevice design built of SMBGs. Not only this novel design increases the angular and spectral range of the PBS microdevice in comparison to conventional PBS designs, but most importantly, our microdevice can operate with normally incident light, acting as a high-efficiency polarization-selective mirror. Microdevice with such features are critical for microlaser designs. Since the SMBG is a 2-D periodic structure, it can also be used to design a 2-D photonic crystal. In this manuscript, we summarize the design, modeling, and characterization of the SMBG structure designed to implement polarization sensitive microdevice, and also introduce and discuss a 2-D photonic crystal design based on SMBG.
{"title":"Subwavelength Multilayer Binary Grating Design for Implementing Photonic Crystals","authors":"R. Tyan, P. Sun, A. Salvekar, H. Chou, Chuan-cheng Cheng, F. Xu, A. Scherer, Y. Fainman","doi":"10.1364/qo.1997.qtha.4","DOIUrl":"https://doi.org/10.1364/qo.1997.qtha.4","url":null,"abstract":"Subwavelength multilayer binary gratings (SMBG) can be seen as a 2-D periodic structures (see Fig.1a) with two periodic directions along the grating vector and the multilayer cascading direction. Such structures combine strong form- birefringence1,2 of the subwavelength grating with high reflectivity due the multilayer structure allowing us to design polarization sensitive microdevices, such as polarization selective mirror and polarizing beam splitter. Recently3 we introduce a new polarizing beam splitter (PBS) microdevice design built of SMBGs. Not only this novel design increases the angular and spectral range of the PBS microdevice in comparison to conventional PBS designs, but most importantly, our microdevice can operate with normally incident light, acting as a high-efficiency polarization-selective mirror. Microdevice with such features are critical for microlaser designs. Since the SMBG is a 2-D periodic structure, it can also be used to design a 2-D photonic crystal. In this manuscript, we summarize the design, modeling, and characterization of the SMBG structure designed to implement polarization sensitive microdevice, and also introduce and discuss a 2-D photonic crystal design based on SMBG.","PeriodicalId":44695,"journal":{"name":"Semiconductor Physics Quantum Electronics & Optoelectronics","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"1997-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87465869","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
It seems fair to say that the polarization behavior of semiconductor Vertical-Cavity Surface-Emitting Lasers (VCSELs) is not understood on a fundamental level. In spite of the nominal anisotropy of a VCSEL the polarization is usually reported as being linear, but not very stable. Most authors associate this behavior with native anisotropies due to imperfect device fabrication although also intrinsic nonlinearities of the gain medium have been put forward for explaining the linear polarization. We are involved in a detailed study [1-4] of the various anisotropies of a VCSEL, their interplay, their manipulation and the consequences thereof for the VCSEL polarization. We have found experimentally that the polarization of a practical VCSEL can be largely explained as a consequence of linear anisotropies; nonlinearities play at most a minor role.
{"title":"Symmetry Breaking in Vertical-Cavity Semiconductor Lasers","authors":"J. Woerdman, A. V. van Doorn, M. V. van Exter","doi":"10.1364/qo.1997.qfb.6","DOIUrl":"https://doi.org/10.1364/qo.1997.qfb.6","url":null,"abstract":"It seems fair to say that the polarization behavior of semiconductor Vertical-Cavity Surface-Emitting Lasers (VCSELs) is not understood on a fundamental level. In spite of the nominal anisotropy of a VCSEL the polarization is usually reported as being linear, but not very stable. Most authors associate this behavior with native anisotropies due to imperfect device fabrication although also intrinsic nonlinearities of the gain medium have been put forward for explaining the linear polarization. We are involved in a detailed study [1-4] of the various anisotropies of a VCSEL, their interplay, their manipulation and the consequences thereof for the VCSEL polarization. We have found experimentally that the polarization of a practical VCSEL can be largely explained as a consequence of linear anisotropies; nonlinearities play at most a minor role.","PeriodicalId":44695,"journal":{"name":"Semiconductor Physics Quantum Electronics & Optoelectronics","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"1997-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87714745","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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