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Elliptical line focus in fluorescence spectroscopy : theory and application

Hans Blom, Niklas Bark, Michael Gösch, Erik Forsberg, Toni Heino, Johan Holm, Gunnar G. Bjork, Rudolf W. Rigler

Published Jan 1, 2010• 0 citations
OpenAlex

Abstract

Correlation analysis and correlation spectroscopy has eversince the first developments, to characterise light emittingprocesses and biomolecular dynamics, continued to extend itspractical applicability. Today, correlation spectroscopy can beused in life science to study dynamical processes even at thesingle molecule level. Correlation analysis can in one of itsextreme be applied to investigate single photon processes fromsolid-state emitters. This thesis is an account of my studiesof fluorescent emitter related to quantum optics and lifescience. It presents some fundamental results and discussesapplications of emitters like single quantum dots or singledyes attached to biomolecules. The studies were performed bythe means of correlation analysis and correlation spectroscopyon self-made optical setups. One task of this thesis was todevelop fluorescence correlation spectroscopy for ultravioletexcitation and emission. With ultraviolet excitation thenatural intrinsic chromophores of certain nucleotides and aminoacids can be used. No external labelling of biomolecules couldbecome a reality using ultraviolet excitation and emission. Asecond task was to apply correlation spectroscopy to performhigh spatial-resolution flow profiling and trafficking ofsingle dye-labeled biomolecules in microstructured channels.Future transports effects, flow monitoring, flow profiling andprolonged fluorescence detection in artificial microstructuresor in cells, could benefit from this application. An additionaltask was to apply correlation spectroscopy to so-calledmicroarrays for parallel acquisition of dynamical data at thesingle molecule level. Parallel excitation and detection wasachieved with the use of diffractive optical elements andintegrated semiconductor single-photon sensitive detectors. Thecurrent throughput rate in biological diagnostic or screeninganalysis could be increased dramatically with implementation ofthis parallel confocal excitation and detection technique. Yetanother task of this thesis was to investigations single-photongeneration by InAs-semiconductor quantum dots. We show that aquantum dots can be used for single-photon generation ondemand. Besides the single-photon generation in quantum dots,the possibility of two-photon generation, and generation ofentangled photon-pair, has also been investigated

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Fluorescence correlation spectroscopy with Lorentzian intensity distribution

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Correlation analysis and correlation spectroscopy has eversince the first developments, to characterise light emittingprocesses and biomolecular dynamics, continued to extend itspractical applicability. Today, correlation spectroscopy can beused in life science to study dynamical processes even at thesingle molecule level. Correlation analysis can in one of itsextreme be applied to investigate single photon processes fromsolid-state emitters. This thesis is an account of my studiesof fluorescent emitter related to quantum optics and lifescience. It presents some fundamental results and discussesapplicationsof emitters like single quantum dots or singledyes attached to biomolecules. The studies were performed bythe means of correlation analysis and correlation spectroscopyon self-made optical setups. One task of this thesis was todevelop fluorescence correlation spectroscopy for ultravioletexcitation and emission. With ultraviolet excitation thenatural intrinsic chromophores of certain nucleotides and aminoacids can be used. No external labelling of biomolecules couldbecome a reality using ultraviolet excitation and emission. Asecond task was to apply correlation spectroscopy to performhigh spatial-resolution flow profiling and trafficking ofsingle dye-labeled biomolecules in microstructured channels.Future transports effects, flow monitoring, flow profiling andprolonged fluorescence detection in artificial microstructuresor in cells, could benefit from this application. An additionaltask was to apply correlation spectroscopy to so-calledmicroarrays for parallel acquisition of dynamical data at thesingle molecule level. Parallel excitation and detection wasachieved with the use of diffractive optical elements andintegrated semiconductor single-photon sensitive detectors. Thecurrent throughput rate in biological diagnostic or screeninganalysis could be increased dramatically with implementation ofthis parallel confocal excitation and detection technique. Yetanother task of this thesis was to investigations single-photongeneration by InAs-semiconductor quantum dots. We show that aquantum dots can be used for single-photon generation ondemand. Besides the single-photon generation in quantum dots,the possibility of two-photon generation, and generation ofentangled photon-pair, has also been investigated.

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Correlation spectrosopy of single eitters : fundamental studies and applications related to quantum optics and life science

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Photon correlations probe the quantized nature of light emission from optoelectronic materials

John M. Lupton, Jan Vogelsang

Even though the quantized interaction between light and matter in the photoelectric effect is considered one of the cornerstones in the development of quantum mechanics, it was long thought impossible to directly observe the quantized nature of light itself. The advent of light-intensity autocorrelation techniques in the 1950s, first developed to study the size of stars, changed little in this perception, until true single-photon correlation spectroscopy from trapped ions was proven to be possible in the late 1970s: Photons from a single quantum emitter tend to arrive in bunches, but each light quantum is spaced apart in time—it is antibunched. Initially considered only as the workhorse of atomic quantum optics, over the past two decades, photon correlation techniques have become a standard in fields as diverse as quantum-information processing, biological imaging, polymer physics, and materials science, in general. The technique is particularly useful for probing materials that are specifically designed to emit or absorb light in optoelectronic devices, such as light-emitting diodes, solar cells, or lasers. The central question in such studies is how large a mesoscopic piece of material can become and still behave as an atom-like source of single photons. What interactions may arise between multiple excitations within a material, and what sort of dark states may give rise to intermittency in the stream of photons? We review the many different classes of optoelectronic materials for which photon-correlation spectroscopy has proven to offer useful insight into excited-state dynamics, ranging from molecular, over semiconductor to metallic nanostructures. The technique is particularly suited to probing mesoscopic aggregates of organic semiconductors since each single molecule acts as a quantum emitter itself.

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Quantum Information and Quantum Correlations of Single-Photon Emitters

Christoph Thiel

This thesis summarizes investigations on quantum correlations in the fluorescence light of single trapped atoms. The results found have applications in the broad field of quantum information science: it is shown how to overcome classical imaging boundaries using a new developed scheme of quantum imaging, how to project and engineer correlated quantum states in the ground states of multi-level atoms by detecting their fluorescence light and how to prove the quantum nature of these correlations using fundamental tests of quantum information science. Without the need of further introduction to these topics it is interesting to note at this early point that all correlations observed are indeed of quantum nature and show in particular entanglement features, while initially the system under consideration is entirely uncorrelated and the only intervention comes along with the measurement process itself. Therefore, this thesis is embedded into a current field of research activities in the area of quantum information science which is commonly referred to as measurement-induced entanglement. In the first part of this thesis, the correlated photon signal as measured in the fluorescence light of single-photon emitters is at the focus of investigations. It is shown that this correlated signal can be used to overcome classical signals in terms of resolution when applied to image processing. In the second part, the fluorescence signal of a system of multi-level atoms is used to project correlated quantum states into the long-lived ground levels of the atoms. Hereby, a broad variety of entangled quantum states can be generated, ranging from symmetric states like the W-states and GHZ-states to arbitrary total angular momentum eigenstates. Finally, the last part of this thesis takes a closer look at the fundamental physical processes inherent in all schemes and applications investigated throughout the thesis. There, amongst others we investigate Bell-type inequalities that are able to prove the quantum nature of the correlations.

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Single Photon Generation and Spectroscopy Using Quantum Dots on Optical Nanofibers

Ramachandrarao Yalla

This thesis presents single photon generation and spectroscopy using quantum dots (q-dots) on optical nanofibers. Optical nanofibers are essentially vacuum-clad silica fibers with sub-wavelength diameter, which can support only the propagation of the fundamental mode through the guided mode. Optical nanofibers are realized using adiabatically tapered single mode optical fibers. Experiments were performed by depositing colloidal core-shell type CdSeTe (ZnS) q-dots on the optical nanofiber surface. A method is developed to deposit single q-dots systematically and reproducibly along the optical nanofiber. In the view point of investigation of fluorescence photon emission characteristics for single q-dots on optical nanofibers, the absolute fluorescence photon-count rates channeled into the nanofiber guided modes and the normalized photon correlations at various excitation laser intensities are measured. The results are able to obtain the product between the fluorescence photon channeling efficiency and the quantum efficiency of the single q-dots. However, the channeling efficiency cannot be determined without accurate information on the quantum efficiency of the single q-dots. Therefore, a method is devised to determine the channeling of fluorescence photons from single q-dots into the guided modes by measuring the fluorescence photon-count rates through the guided and radiation modes simultaneously. By measuring for various nanofiber diameters, a maximum channeling efficiency obtained to be 22.0 (±4.8)% at a fiber diameter of 350 nm for an emission wavelength of 780 nm. The measured results completely reproduce the theoretical predictions within the experimental error. We demonstrate in situ measurements of fluorescence quantum efficiency of single q-dots using the present nanofiber technique. We determine fluorescence quantum efficiency of single q-dots accurately by assuming the theoretical values for the channeling efficiency from the product of the channeling efficiency and the quantum efficiency. We demonstrate that one can pick up one q-dot on the nanofiber with fluorescence quantum efficiency higher than the average value measured for an ensemble. Thus, the optical nanofiber method offers a promising way for generating and manipulating single photons. This work should provide a basis for extending the optical nanofiber method to a general technique in quantum optics, which may open new possibilities in quantum information technologies.

•Jan 1, 2012•1 citation
Correlation analysis and correlation spectroscopy has eversince the first developments, to characterise light emittingprocesses and biomolecular dynamics, continued to extend itspractical applicability. Today, correlation spectroscopy can beused in life science to study dynamical processes even at thesingle molecule level. Correlation analysis can in one of itsextreme be applied to investigate single photon processes fromsolid-state emitters. This thesis is an account of my studiesof fluorescent emitter related to quantum optics and lifescience. It presents some fundamental results and discussesapplications of emitters like single quantum dots or singledyes attached to biomolecules. The studies were performed bythe means of correlation analysis and correlation spectroscopyon self-made optical setups. One task of this thesis was todevelop fluorescence correlation spectroscopy for ultravioletexcitation and emission. With ultraviolet excitation thenatural intrinsic chromophores of certain nucleotides and aminoacids can be used. No external labelling of biomolecules couldbecome a reality using ultraviolet excitation and emission. Asecond task was to apply correlation spectroscopy to performhigh spatial-resolution flow profiling and trafficking ofsingle dye-labeled biomolecules in microstructured channels.Future transports effects, flow monitoring, flow profiling andprolonged fluorescence detection in artificial microstructuresor in cells, could benefit from this application. An additionaltask was to apply correlation spectroscopy to so-calledmicroarrays for parallel acquisition of dynamical data at thesingle molecule level. Parallel excitation and detection wasachieved with the use of diffractive optical elements andintegrated semiconductor single-photon sensitive detectors. Thecurrent throughput rate in biological diagnostic or screeninganalysis could be increased dramatically with implementation ofthis parallel confocal excitation and detection technique. Yetanother task of this thesis was to investigations single-photongeneration by InAs-semiconductor quantum dots. We show that aquantum dots can be used for single-photon generation ondemand. Besides the single-photon generation in quantum dots,the possibility of two-photon generation, and generation ofentangled photon-pair, has also been investigated
Correlation analysis and correlation spectroscopy has eversince the first developments, to characterise light emittingprocesses and biomolecular dynamics, continued to extend itspractical applicability. Today, correlation spectroscopy can beused in life science to study dynamical processes even at thesingle molecule level. Correlation analysis can in one of itsextreme be applied to investigate single photon processes fromsolid-state emitters. This thesis is an account of my studiesof fluorescent emitter related to quantum optics and lifescience. It presents some fundamental results and discussesapplicationsof emitters like single quantum dots or singledyes attached to biomolecules. The studies were performed bythe means of correlation analysis and correlation spectroscopyon self-made optical setups. One task of this thesis was todevelop fluorescence correlation spectroscopy for ultravioletexcitation and emission. With ultraviolet excitation thenatural intrinsic chromophores of certain nucleotides and aminoacids can be used. No external labelling of biomolecules couldbecome a reality using ultraviolet excitation and emission. Asecond task was to apply correlation spectroscopy to performhigh spatial-resolution flow profiling and trafficking ofsingle dye-labeled biomolecules in microstructured channels.Future transports effects, flow monitoring, flow profiling andprolonged fluorescence detection in artificial microstructuresor in cells, could benefit from this application. An additionaltask was to apply correlation spectroscopy to so-calledmicroarrays for parallel acquisition of dynamical data at thesingle molecule level. Parallel excitation and detection wasachieved with the use of diffractive optical elements andintegrated semiconductor single-photon sensitive detectors. Thecurrent throughput rate in biological diagnostic or screeninganalysis could be increased dramatically with implementation ofthis parallel confocal excitation and detection technique. Yetanother task of this thesis was to investigations single-photongeneration by InAs-semiconductor quantum dots. We show that aquantum dots can be used for single-photon generation ondemand. Besides the single-photon generation in quantum dots,the possibility of two-photon generation, and generation ofentangled photon-pair, has also been investigated.
Even though the quantized interaction between light and matter in the photoelectric effect is considered one of the cornerstones in the development of quantum mechanics, it was long thought impossible to directly observe the quantized nature of light itself. The advent of light-intensity autocorrelation techniques in the 1950s, first developed to study the size of stars, changed little in this perception, until true single-photon correlation spectroscopy from trapped ions was proven to be possible in the late 1970s: Photons from a single quantum emitter tend to arrive in bunches, but each light quantum is spaced apart in time—it is antibunched. Initially considered only as the workhorse of atomic quantum optics, over the past two decades, photon correlation techniques have become a standard in fields as diverse as quantum-information processing, biological imaging, polymer physics, and materials science, in general. The technique is particularly useful for probing materials that are specifically designed to emit or absorb light in optoelectronic devices, such as light-emitting diodes, solar cells, or lasers. The central question in such studies is how large a mesoscopic piece of material can become and still behave as an atom-like source of single photons. What interactions may arise between multiple excitations within a material, and what sort of dark states may give rise to intermittency in the stream of photons? We review the many different classes of optoelectronic materials for which photon-correlation spectroscopy has proven to offer useful insight into excited-state dynamics, ranging from molecular, over semiconductor to metallic nanostructures. The technique is particularly suited to probing mesoscopic aggregates of organic semiconductors since each single molecule acts as a quantum emitter itself.
This thesis summarizes investigations on quantum correlations in the fluorescence light of single trapped atoms. The results found have applications in the broad field of quantum information science: it is shown how to overcome classical imaging boundaries using a new developed scheme of quantum imaging, how to project and engineer correlated quantum states in the ground states of multi-level atoms by detecting their fluorescence light and how to prove the quantum nature of these correlations using fundamental tests of quantum information science. Without the need of further introduction to these topics it is interesting to note at this early point that all correlations observed are indeed of quantum nature and show in particular entanglement features, while initially the system under consideration is entirely uncorrelated and the only intervention comes along with the measurement process itself. Therefore, this thesis is embedded into a current field of research activities in the area of quantum information science which is commonly referred to as measurement-induced entanglement. In the first part of this thesis, the correlated photon signal as measured in the fluorescence light of single-photon emitters is at the focus of investigations. It is shown that this correlated signal can be used to overcome classical signals in terms of resolution when applied to image processing. In the second part, the fluorescence signal of a system of multi-level atoms is used to project correlated quantum states into the long-lived ground levels of the atoms. Hereby, a broad variety of entangled quantum states can be generated, ranging from symmetric states like the W-states and GHZ-states to arbitrary total angular momentum eigenstates. Finally, the last part of this thesis takes a closer look at the fundamental physical processes inherent in all schemes and applications investigated throughout the thesis. There, amongst others we investigate Bell-type inequalities that are able to prove the quantum nature of the correlations.
This thesis presents single photon generation and spectroscopy using quantum dots (q-dots) on optical nanofibers. Optical nanofibers are essentially vacuum-clad silica fibers with sub-wavelength diameter, which can support only the propagation of the fundamental mode through the guided mode. Optical nanofibers are realized using adiabatically tapered single mode optical fibers. Experiments were performed by depositing colloidal core-shell type CdSeTe (ZnS) q-dots on the optical nanofiber surface. A method is developed to deposit single q-dots systematically and reproducibly along the optical nanofiber. In the view point of investigation of fluorescence photon emission characteristics for single q-dots on optical nanofibers, the absolute fluorescence photon-count rates channeled into the nanofiber guided modes and the normalized photon correlations at various excitation laser intensities are measured. The results are able to obtain the product between the fluorescence photon channeling efficiency and the quantum efficiency of the single q-dots. However, the channeling efficiency cannot be determined without accurate information on the quantum efficiency of the single q-dots. Therefore, a method is devised to determine the channeling of fluorescence photons from single q-dots into the guided modes by measuring the fluorescence photon-count rates through the guided and radiation modes simultaneously. By measuring for various nanofiber diameters, a maximum channeling efficiency obtained to be 22.0 (±4.8)% at a fiber diameter of 350 nm for an emission wavelength of 780 nm. The measured results completely reproduce the theoretical predictions within the experimental error. We demonstrate in situ measurements of fluorescence quantum efficiency of single q-dots using the present nanofiber technique. We determine fluorescence quantum efficiency of single q-dots accurately by assuming the theoretical values for the channeling efficiency from the product of the channeling efficiency and the quantum efficiency. We demonstrate that one can pick up one q-dot on the nanofiber with fluorescence quantum efficiency higher than the average value measured for an ensemble. Thus, the optical nanofiber method offers a promising way for generating and manipulating single photons. This work should provide a basis for extending the optical nanofiber method to a general technique in quantum optics, which may open new possibilities in quantum information technologies.