This dissertation presents the structure, operational principle and mathematical model of a novel high speed fiber optic spectrometer (HSFOS). In addition, the performance analysis is conducted and preliminary experimental results are listed and discussed. Such a spectrometer is highly desired by the ever-increasing applications of fiber optic sensors. In the recent decades, a variety of fiber optic sensors have been proposed, built and tested. Compared to their electronic counterparts, fiber optic sensors although still under development, are preferred more by certain industrial and medical applications which benefit from their unique properties such as immunity to electromagnetic interference, ability to withstand harsh environments and composition of purely dielectric materials. In recent years, new fiber optic sensors have been designed for applications where high response frequency up to a few hundred KHz is required while advantages of high accuracy and large dynamic range must be maintained. The bottle neck then emerged in the signal demodulation part of the sensor system. The quadrature phase detection could achieve high demodulation speed but with small dynamic range, medium accuracy and measurement ambiguity. The white light interferometry could provide a solution for high accuracy and large dynamic range measurement without ambiguity because of its absolute measurement nature. However the signal demodulation speed is limited due to the low spectrum acquisition rate of the existing spectrometers. The new HSFOS utilizes time domain dispersion of the sampled incoming light by dispersive fiber rather than the spatial dispersion employed by traditional spectrometers. In addition the signal that represents the spectrum of the light is naturally a serial signal which can be detected by a single detector and recorded by a high speed data acquisition device. Theoretical study of the operation principle is made and a mathematical model for the spectrometer is developed based on Marcuse's previous work. One major difference of the new derivation is that the propagation constant is expanded about the center circular frequency of each monochromatic light pulse instead of the center frequency of the chromatic light pulse which makes the physical picture of the chromatic light pulse evolution in a dispersive fiber clearer and facilitates both the analytical and numerical analysis. The profile of the dispersed chromatic light pulse could be treated as the superposition of all the dispersed monochromatic light pulses. Another major difference is the Taylor's series of the propagation constant is not truncated as it is in those previous work, which improves the accuracy of the model. Moreover, an approximate model is made which could further reduce the computation tasks in numerical simulations. Performance analysis for accuracy, resolution, speed and noise are conducted through numerical simulations based on the model and the experimental results. The sources of two different errors and their effects on accuracy are discussed respectively. The effects on spectral resolution by the properties of the modulation pulse and the fiber dispersion are studied. The results indicate that by using a rectangle modulation pulse under certain conditions, the resolution can be improved. The speed analysis gives that the spectrum acquisition rate can reach 1 million frames per second when the spectral width is less than 100 nm. In the noise analysis, the erbium-doped fiber amplifier (EDFA) is determined to be the dominant noise source. But by using two EDFAs, the overall signal to noise ratio is improved by 9.2 dB. The preliminary experimental results for FP sensor and FBG sensor signal demodulation are presented. The HSFOS for FP sensor signal demodulation achieves 15 nm resolution. By using the oversampling method, the HSFOS for FBG sensor signal demodulation achieves 0.05 nm spectral positioning resolution. / Ph. D.

An (e,2e) electron scattering spectrometer has been constructed and used for the first time to investigate the spectral momentum density of the valence bands of a solid target. This technique provides fundamental information about the electronic structure of both crystalline and amorphous solids. The three fundamental quantities, the band structure, electron density of states, and electron momentum distribution can be simultaneously derived from the measured (e,2e) cross section. A review of single electron and (e,2e) scattering theory is given with an emphasis on scattering from solids. The effects of multiple scattering are discussed and a method of deconvoluting those effects from the measured (e,2e) cross section is developed. There is a detailed description of the spectrometer design and operation with particular attention given to the electron optics and voltage distribution. The algorithms and software for computer aided data acquisition and analysis are also outlined, as is error analysis. The techniques employed in the preparation and characterization of extremely thin film samples of a-C and single crystal graphite are described. An analysis of the data taken for a-C samples is given. The data are compared with the results of complementary experiments and theory for graphite, diamond, and a-C which are given in a review of the literature. The existence of a definite dispersion relation ε(q) in amorphous carbon is demonstrated. The a-C band structure appears to be more similar to that of graphite than to that of diamond, however it differs significantly from both in some respects. The measured spectral momentum density seems compatible with a model of a-C based on small, randomly-oriented islands of quasi-2D graphite-like continuous random network structures. However, no definitive interpretations can be made until higher resolution experiments are performed on both a-C and single crystal graphite. / Ph. D.

The electron energy loss spectrometer at Virginia Tech has been modified with new momentum deflectors and various other hardware improvements. In addition to some hardware changes all the software to run the spectrometer and analyze the data has been rewritten. It was suggested by Tsuei (1990) that a nested Fermi surface could be used to explain both the fact that these materials have high superconducting transition temperatures and have linear relaxation rates. It was suggested in that same paper that EELS might be able to confirm the presence of Fermi surface nesting. We have attempted to use transmission electron energy loss spectroscopy in a novel way to search for evidence of Fermi surface nesting in the high T_c superconductor Bi₂Sr₂Ca₁Cu₂O₈. High quality single crystal samples were obtained and thinned for use in the EELS. Data was taken at low energy (<1.0eV) and momentum was scanned along three different momentum transfer directions for |q| =0.0 to 3.0Å⁻¹. The data was scaled to be Im(-1/ε). A calculation of Im(-1/ε) was performed using a tight binding model and it was found that the features associated with the Fermi surface (from this TB calculation) were too small to be seen in our spectra. We interpret this problem to be associated with the presence of thermal diffuse scattering. / Ph. D.

The spins of phosphorus doped in silicon are potential candidates for a quantum computing device, with models based on the use of nuclear and/or electron spins suggested. For a quantum computing device, several essential criteria must be demonstrated before any physical implementation, and these include qubit control gates, long decoherence time and scalability. Scalability and compatibility with existing fabrication technologies are strong points in favour of a silicon based system. For spin based schemes, silicon has the potential to provide a host with zero nuclear spin (isotopically purifed 28Si) and also the phosphorus donor provides both nuclear and electron half integer spins (ideal case). In this work, a magnetic resonance method (electron spin resonance) was utilised to investigate these critical issues (controllable quantum gates and decoherence time) for the electron spins of phosphorus donors in silicon. Electron spin resonance (ESR) studies of an ensemble of phosphorus electron spins in silicon were conducted via both continuous wave and pulsed methods. For pulsed ESR operations, two low temperature (4 K and millikelvin) X-band pulsed ESR systems were built. They were designed especially to suit Si:P decoherence time measurements. The design, modelling, construction and evaluation of the probe heads are described. With the aid of computer simulations, the performance of the probe heads was optimised and a rectangular loop gap resonator was found to be the most suitable for wafer type samples. The resonant frequency, quality factor, and coupling coeffcient were calculated via simulation and are in reasonable agreement with experimental results. This demonstrates the effectiveness of such simulations as a tool for optimising the probe head performance. A millikelvin pulsed ESR system was set up through the combination of a dilution refrigerator, superconducting magnet and the in-house construction of a pulsed ESR spectrometer. This novel system allows pulsed ESR experiments on an ensemble system to be realised down to the millikelvin temperature range, hence providing conditions considered most favourable for quantum computing studies. The use of light in combination with the pulsed ESR systems was also explored in an endeavour to overcome the problem of very long spin-lattice relaxation time, T1, allowing the decoherence time to be measured more effciently. With these novel low temperature pulsed ESR units, two-pulse electron spin echo experiments were conducted on phosphorus donors in silicon (both natural silicon (natSi) and 28Si) with the phosphorus concentration in the range of 1015- 1016 P/cm3 and to lower temperatures than previously investigated. Decoherence times measured for both natSi:P and 28Si:P (with similar donor concentrations) were longer than previously reported. Discussions on several effective ways to obtain even longer Si:P decoherence times including variations to sample configurations and experimental conditions are presented. In addition to the pulsed ESR studies, the Si:P controllable quantum gate functions, A gate and J gate, were examined by the continuous wave technique via Stark shift and exchange interaction experiments respectively. Stark shift experiments on bulk samples were carried out to investigate possible manipulation of the spins by the applied electric field. Continuous wave ESR was also used to examine low energy ion implanted Si:P devices, both by single (P+) and dimer (P+2 ) implanted donors. The outcomes from these studies provide materials information useful in formulating a strategy toward the Si:P device fabrication via the top down approach.

The role of clusters in planetary atmospheres and the interstellar medium is potentially important. Investigating such a role requires basic experimental information, however lacking. The goal of this thesis was to develop an efficient experimental set-up to produce clusters in the laboratory in concentrations large enough to allow their high resolution spectra to be recorded, thus providing the necessary data allowing the physico-chemical properties of the clusters to be studied. The study of this subject however suffers from the lack of basic experimental data. The goal is therefore to produce clusters in the laboratory in concentration large enough to record their high resolution spectrum. This is the initial aim of the present thesis. During this work, we have built and extensively tested a new experimental set-up called FANTASIO (``Fourier trANsform, Tunable diode and quadrupole mAss spectrometers interfaced to a Supersonic expansIOn'). With the help of this new device, various experiments on jet-cooled species have been performed. The cartography of the supersonic expansion was established, using the mass spectrometer as a moving pressure probe. This enabled us to characterize the geometrical properties of the supersonic jet produced by circular and slit nozzles and to determine the position of the virtual nozzle. The effect of the axisymmetric expansion geometry on the R(0) lineshape in the nu_3 band of N_2O, recorded by FTIR, was also investigated. The rotational temperature of the jet-cooled molecules was determined to be a few K by measuring the intensity of lines in spectra recorded by FTIR spectroscopy. Vibrational energy transfer occuring in the expansion between N_2O molecules and different collision partners was investigated on the nu_2+nu_3-nu_2 band of N_2O, again using FTIR spectroscopy. The trend of these transfers was found to be related to the energy difference between the v_2=1 level of N_2O and the closest vibrational state in the collision partner, with the largest population. The sensitivity of the set-up was enhanced by a factor of 5 by increasing the absorption path length, using a multipass system. A procedure to remove the residual gas contribution from the IR spectra was developped, based on the mass spectrometer. Thanks to this sensitivity increase, broadband absorption features of clusters were observed for a C_2H_2-Ar mixture in circular and slit expansions. The optical sensitivity of FANTASIO was again increased by the implementation of the CW-CRDS system. The enhancement over FTIR was calculated to be over a factor 750. Thanks to this drastic improvement, spectral signatures of various clusters were recorded, such as C_2H_2-Ar, C_2H_2 multimers, C_2H_2-N_2O and C_2H_2-CO_2, at high resolution. The role of clustering in generating unusual line shapes of acetylene in an axisymmetric expansion was investigated. We demonstrated that C_2H_2 aggregates produced in the expansion are responsible for central dips observed in the monomer absorption. These acetylene clusters thus appear to be formed in the centre of the expansion, while, unexpectedly, acetylene-Ar complexes are formed at the edge of the conical expansion. Various research prospects were explored during this thesis thanks to the FANTASIO device, opening new research directions. FANTASIO is today operational and defines a useful tool to achieve the study of small clusters by infrared spectroscopy./ Le rôle des agrégats dans les atmosphères planétaires et dans le milieu interstellaire est potentiellement important. Cependant, les études sur ce sujet souffrent du manque de données expérimentales. Le but de cette thèse était de développer un dispositif expérimental efficace pour produire au laboratoire des agrégats en quantité suffisante pour permettre l'enregistrement de leur spectre infrarouge à haute résolution et donc l'étude de leurs propriétés physico-chimiques. Durant ce travail, nous avons construit et testé un nouveau dispositif expérimental appelé FANTASIO, basé sur un jet supersonique couplé à un spectromètre de masse, un spectromètre à transformée de Fourier et un système CRDS. Grâce à cet appareillage, différentes expériences sur des molécules à basse température ont été menées. L'expansion supersonique a été cartographiée en utilisant le spectromètre de masse comme une sonde de pression mobile. Cette cartographie nous a permis d'établir les propriétés géométriques des jets supersoniques produits par les orifices circulaire et de type fente, et de déterminer la position de l'orifice virtuel. L'effet de la géométrie de l'expansion sphérique sur le profil de la raie R(0) de la bande nu_3 de N_2O, enregistré par FTIR, a aussi été étudié. Une température rotationnelle de quelques K a été déterminée pour les molécules refroidies en jet supersonique par mesure de la distribution d'intensité de raies dans les spectres enregistrés par FTIR. Le transfert d'énergie vibrationnelle entre des molécules de N_2O et différents partenaires collisionnels a été étudié en analysant l'intensité de la bande nu_2+nu_3-nu_2 de N_2O, enregistré également par spectroscopie FTIR. Il a été trouvé que la tendance de ces transferts est liée à la différence d'énergie entre le niveau v_2=1 de N_2O et l'état vibrationnel le plus proche et le plus peuplé du partenaire collisionnel. La sensibilité du dispositif a été augmentée d'un facteur 5 dû à l'allongement du chemin d'absorption, grâce à l'utilisation d'un système multipassage. Une procédure basée sur l'utilisation du spectromètre de masse et visant à enlever la contribution du gaz chaud résiduel dans les spectres infrarouges a été mise au point. Grâce à cette augmentation de sensibilité, des structures d'absorption non résolues d'agrégats ont été observées dans des expansions en trou et en fente d'un mélange de C_2H_2-Ar. La sensibilité optique de FANTASIO a encore été augmentée par l'ajout au dispositif d'un système CW-CRDS. L'amélioration par rapport au spectromètre à transformée de Fourier a été calculée comme étant supérieure à un facteur 750. Grâce à cette importante amélioration, les signatures spectrales de divers agrégats, tels que C_2H_2-Ar, des multimères de C_2H_2, C_2H_2-N_2O et C_2H_2-CO_2, ont été enregistrées à haute résolution. Le rôle de l'agrégation dans la génération de profils de raie inhabituels dans une expansion en trou de l'acétylène a été étudié. Nous avons démontré que les agrégats de C_2H_2 produits dans le jet supersonique sont responsables des creux observés dans le profil d'absorption du monomère. Ces agrégats apparaissent donc comme étant formés au centre de l'expansion, tandis que, de manière inattendue, les agrégats de C_2H_2-Ar sont formés aux bords de l'expansion conique. Plusieurs idées de recherche ont été explorées durant cette thèse grâce au dispositif FANTASIO, ouvrant de nouvelles directions de recherche. FANTASIO est aujourd'hui opérationnel et se présente comme un outil utile dans l'étude des petits agrégats par spectroscopie infrarouge.

Work reported in this thesis mainly comprises of the assignments and analysis of the rotational spectra and structures of three weakly bound complexes: C2H4•••H2S, C6H5CCH•••H2O and C6H5CCH•••H2S. All the data have been collected using a home built Pulsed Nozzle Fourier Transform Microwave Spectrometer. Apart from this, the thesis also deals with a criterion of classifying a weakly bound complex to a ‘hydrogen-bonded’ one. First chapter of the thesis gives a brief intermolecular interactions and molecular clusters of π system. It also briefly touches on the structural determination by rotational spectroscopy and the basic information one can gain from the rotational spectrum. Second chapter of the thesis gives a brief introduction to the experimental and theoretical methodology. It also gives a description of the software used in the FTMW spectrometer which was rebuilt using Labview 7.1. Third chapter of the thesis deals with the rotational spectra and structure of eight isotopologoues of C2H4•••H2S complex. The lines are split into four components for the parent isotopologue due to the presence of large amplitude motion. The smaller splitting is 0.14 MHz and the higher splitting is 1.67 MHz in (B+C)/2 for the parent isotopologue. Spectral splitting pattern of the isotopologues confirmed that smaller splitting is due to the rotation of ethylene about its C-C bond axis along with the contraction of S-H bond whereas the larger motion arises due to the interchange of equivalent hydrogens of H2S in the complex. A detailed spectral analysis and ab initio calculation for this system have been described in chapter III. The fourth chapter of the thesis describes the rotational spectroscopic studies of five isotopologues of C6H5CCH•••H2O complex. Rotational spectra unequivocally confirm the structure of the complex to be a one where H2O is donating one of its hydrogen to the acetylenic π cloud forming a O-H••• π bond whereas the ring ortho C-H bond forms C-H•••O bond with the water oxygen. For theparent isotopomer the lines are split into two components due to the rotation of H2O about its C2 symmetric axis. The fifth chapter of thesis describes the rotational spectroscopic and ab initio studies of five isotopologues of C6H5CCH•••H2S complex. Rotational spectra indicate the structure to be the one where H2S is sitting on the top of the phenyl ring and shifted towards the acetylenic group. The sixth chapter of the thesis describes a criterion for calling a complex to be hydrogen bonded based on the dynamic structure rather than the static structure of the complex. The question asked is if the anisotropy of the interaction is strong enough to hold the ‘hydrogen bond’ when one takes dynamics into account. The proposed criterion is that the zero point energy of the motion which takes the hydrogen away from the acceptor should be much less than the barrier height of the respective motion supporting at least one bound level below the barrier. Ab initio calculations have been done on four model systems Ar2•••H2O, Ar2•••H2S, C2H4••• H2O and C2H4••• H2S to emphasize this criterion.

This thesis presents axially symmetric equivalents of three-dimensional rf ion traps. Miniaturization in mass spectrometry has focused on miniaturizing mass analyzers. Decrease in mass analyzer size facilitates reduction of the size of other components of a mass spectrometer, especially the radio frequency electronics and vacuum system. Miniaturized mass analyzers are made using advanced microfabrication techniques. Due to micromachining limitations, it is not possible to fabricate ion traps with exact axial symmetry. The motivation for this thesis is to investigate newer three-dimensional geometries which do not possess axial symmetry, but are equivalent in performance to axially symmetric ion traps. We introduce a 3D geometry called square ion trap(SIT) having a ring electrode made off our square shaped planar surfaces and square shaped endcap electrodes resembling a cuboid. Initially, a SIT geometry is taken and it will be investigated if this unknown 3D geometry can be made equivalent to a well characterized, axially symmetric ion trap like the CIT. The purpose of showing equivalence will be to understand the ion dynamics and fields inside the new 3D SIT. This thesis consists of five chapters. In Chapter 1, we present the necessary background information required to understand the operation of a mass spectrometer. The Paul trap geometry is introduced followed by the derivation of equation of ion motion inside the Paul trap. The Mathieu stability plot and the modes of operation of a mass spectrometer are briefly discussed. The chapter ends by outlining scope of the thesis. Chapter 2 describes the computational methods employed by us in the thesis. First, the geometry of square ion trap is introduced. Then the boundary element method(BEM) which is used to compute the charge distribution on the electrode surfaces is discussed. This is followed by the three-dimensional Green’s function which should be employed for non-axially symmetric structures. The method to calculate potential and field inside the ion trap from charge distribution is shown. Calculation of multipole coefficients for non-axially symmetric traps using charge distribution is shown. The methods used to generate ion trajectory and stability plot are discussed. The Nelder-Mead simplex method used for optimization is also presented. To verify our numerical methods of charge calculation, we have taken standard textbook problems and compared our results with those presented therein. The multipoles calculation, field and ion trajectory was verified by comparing the results for the Paul trap and cylindrical ion traps. Chapter 3 presents the results for axially symmetric equivalents of 3D rf ion traps. SIT geometry of dimensions equivalent to the CIT0 are taken and field and multipoles are studied in it. Then optimization is applied to create a CIT geometry equivalent to the SIT under study. Axial field and ion trajectory was compared and observed to be matching. Finally, stability plot was generated for both SIT and its equivalent CIT and was found to present a close match. Chapter 4 presents the numerical results obtained for three-dimensional rf ion trap equivalent of CIT. In this chapter, we have considered two standard geometries, the CIT0 and the CITopt. Optimization was applied to create SIT geometries equivalent to the CIT0 and the CITopt respectively. Comparison of fields and ion trajectory confirmed the fact that non-axially symmetric traps can be created equivalent to any axially symmetric ion trap. We have also considered another case of axially symmetric circular planar ion trap which has an annular ring electrode and two planar endcap electrodes. Square equivalent of circular planar trap was created by the optimizer and its equivalent was verified by ion trajectory comparison. Chapter 5 summarizes the thesis with a few concluding remarks.

Durch die Fokussierung eines ultrakurzen und hochintensiven Laserpulses auf ein Festkörpertarget können Pulse von Protonen und anderen positiv geladenen Ionen mit Teilchenenergien von einigen MeV pro Nukleon erzeugt werden. Die Charakterisierung dieser Teilchenstrahlung erfordert die Identifizierung der Ionenspezies und die Bestimmung ihrer spektralen Verteilung möglichst nach jedem Puls. Im Rahmen dieser Diplomarbeit wurden zwei Spektrometer entwickelt und am DRACO-Lasersystem des Forschungszentrums Dresden implementiert. Neben der Inbetriebnahme eines Thomson-Spektrometers mit einer Mikrokanalplatte und einem Fluoreszenzschirm als Auslese erfolgte die Entwicklung eines Flugzeitspektrometers. Die Verwendung einer Mikrokanalplatte mit nur 180ps Anstiegszeit als Signalverstärker sorgt darin für eine verbesserte Energieauflösung und einen flexibleren Einsatz im Experimentierbetrieb. Ein dem Flugzeitsignal überlagertes Störsignal, welches durch die Einstreuungen eines elektromagnetischen Impulses in den Aufbau verursacht wurde, konnte erfolgreich durch die Anwendung verschiedener Filter unterdrückt werden. Als Ergebnis dieser Arbeit steht eine anwendungsbereite Diagnostik für laserbeschleunigte Protonen und Ionen zur Verfügung. / By focusing an ultra-short high-intensity laser pulse on a solid target, pulses of protons and other positive charged ions with energies of several MeV per nucleon are generated. It is necessary to identify the species of those particles and obtain their energy spectra in a single-shot regime. Within this diploma thesis two spectrometers have been developed and implemented in the DRACO-laboratory of the Forschungszentrum Dresden. Besides a Thomson spectrometer with read-out via microchannel plate and phosphor screen, a time-of-flight spectrometer was developed. The usage of a microchannel plate with 180ps rise time as a signal amplifier leads therein to a better energy resolution and a more flexible handling in experimental operation. A noise signal generated by stray pick-up of an electromagnetic pulse and superimposing the time-of-flight signal was considerably reduced by the application of different filters. As a result of this work a ready-to-use diagnostic for laser accelerated protons and ions is available.

Durch die Fokussierung eines ultrakurzen und hochintensiven Laserpulses auf ein Festkörpertarget können Pulse von Protonen und anderen positiv geladenen Ionen mit Teilchenenergien von einigen MeV pro Nukleon erzeugt werden. Die Charakterisierung dieser Teilchenstrahlung erfordert die Identifizierung der Ionenspezies und die Bestimmung ihrer spektralen Verteilung möglichst nach jedem Puls. Im Rahmen dieser Diplomarbeit wurden zwei Spektrometer entwickelt und am DRACO-Lasersystem des Forschungszentrums Dresden implementiert. Neben der Inbetriebnahme eines Thomson-Spektrometers mit einer Mikrokanalplatte und einem Fluoreszenzschirm als Auslese erfolgte die Entwicklung eines Flugzeitspektrometers. Die Verwendung einer Mikrokanalplatte mit nur 180ps Anstiegszeit als Signalverstärker sorgt darin für eine verbesserte Energieauflösung und einen flexibleren Einsatz im Experimentierbetrieb. Ein dem Flugzeitsignal überlagertes Störsignal, welches durch die Einstreuungen eines elektromagnetischen Impulses in den Aufbau verursacht wurde, konnte erfolgreich durch die Anwendung verschiedener Filter unterdrückt werden. Als Ergebnis dieser Arbeit steht eine anwendungsbereite Diagnostik für laserbeschleunigte Protonen und Ionen zur Verfügung. / By focusing an ultra-short high-intensity laser pulse on a solid target, pulses of protons and other positive charged ions with energies of several MeV per nucleon are generated. It is necessary to identify the species of those particles and obtain their energy spectra in a single-shot regime. Within this diploma thesis two spectrometers have been developed and implemented in the DRACO-laboratory of the Forschungszentrum Dresden. Besides a Thomson spectrometer with read-out via microchannel plate and phosphor screen, a time-of-flight spectrometer was developed. The usage of a microchannel plate with 180ps rise time as a signal amplifier leads therein to a better energy resolution and a more flexible handling in experimental operation. A noise signal generated by stray pick-up of an electromagnetic pulse and superimposing the time-of-flight signal was considerably reduced by the application of different filters. As a result of this work a ready-to-use diagnostic for laser accelerated protons and ions is available.

The development and application of new cloud retrieval methods from ground–based and airborne measurements of spectral radiance fields above heteorogeneous surfaces is introduced. The potential of imaging spectrometers in remote–sensing applications is evaluated. The analyzed spectral radiance fields were measured during two international field campaigns in the visible wavelength range (400–970 nm) with high spatial (<10m) resolution. From ground–based measurements, high ice clouds were observed and from airborne measurements Arctic stratus. From the measurements, cloud optical thickness is retrieved with high spatial resolution and the horizontal cloud inhomogeneities are investigated. Depending on the measurement configuration, different uncertainties arise for the retrieval of the cloud optical thickness. A reduction of those uncertainties is derived by a specification of the ice crystal shape to improve the retrieval of the optical thickness of high ice clouds. The ice crystal shape is obtained independently from the angular information of the scattering phase function features, imprinted in the radiance fields. A performed sensitivity study reveals uncertainties of up to 90%, when neglecting this information and applying a wrong crystal shape to the retrieval. For remote-sensing of Arctic stratus, the highly variable surface albedo influences the accuracy of the cloud optical thickness retrieval. In cloudy cases the transition of reflected radiance from open water to sea ice is not instantaneous but horizontally smoothed. In general, clouds reduce the reflected radiance above bright surfaces in the vicinity of open water, while it is enhanced above open sea. This results in an overestimation of to up to 90% in retrievals of the optical thickness. This effect is investigated. Using observations and three-dimensional radiative transfer simulations, this effect is quantified to range to up to 2200 m distance to the sea-ice edge (for dark-ocean albedo of αwater = 0.042 and sea-ice albedo of αice = 0.91 at 645 nm wavelength) and to depend on macrophysical cloud and sea-ice properties. The retrieved fields of cloud optical thickness are statistically investigated. Auto–correlation functions and power spectral density analysis reveal that in case of clouds with prevailing directional cloud structures, cloud inhomogeneities cannot be described by a universally valid parameter. They have to be defined along and across the prevailing cloud structures to avoid uncertainties up to 85%. / Im folgenden wird die Entwicklung und Anwendung neuer Ableitungsverfahren von Wolkenparametern, basierend auf bodengebundener und flugzeuggetragener spektraler Strahldichtemessungen über heterogenen Untergründen, vorgestellt und das Fernerkundungspotential abbildender Spektrometer evaluiert. Die spektralen Strahldichtefelder wurden während zweier internationaler Feldkampagnen im sichtbaren Wellenlängenbereich (400–970 nm) mit hoher räumlich Auflösung (<10m) gemessen. Bodengebundene Messungen wurden genutzt, um hohe Eiswolken zu beobachten und flugzeuggetragenen um arktischen Stratus zu beobachten. Aus den Messungen werden räumlich hochaufgelöste wolkenoptische Dicken abgeleitet und anschließend horizontale Wolkeninhomogenitäten untersucht. Die Ableitung der wolkenoptischen Dicke birgt je nach Messkonfiguration verschiedene Unsicherheiten. Eine Reduzierung der Unsicherheiten wird durch die Vorgabe einer Eiskristallform zur Verbesserung der Ableitung der optischen Dicke hoher Eiswolken erreicht. Diese werden unabhängig aus den winkelabhängigen, in das gemessene Strahldichtefeld eingeprägten Eigenschaften der Streuphasenfunktion, abgeleitet. Bei Vernachlässigung dieser Information und Wahl der falschen Eiskristallform, treten Fehler in der abgeleiteten optischen Dicke von bis zu 90% auf. Bei der Fernerkundung von arktischem Stratus beeinflusst die sehr variable Bodenalbedo die Genauigkeit der Ableitung der optischen Dicke. Beim Übergang von Meereis zu Wasser, findet die Abnahme der reflektierten Strahldichte im bewölktem Fall nicht direkt über der Eiskante, sondern horizontal geglättet statt. Allgemein reduzieren Wolken die reflektierte Strahldichte über Eisflächen nahe Wasser, während sie über dem Wasser erhöht wird. Dies führt zur Überschätzung der wolkenoptischen Dicke über Wasserflächen nahe Eiskanten von bis zu 90 %. Dieser Effekt wird mit Hilfe von Beobachtungen und dreidimensionalen Strahlungstransferrechnungen untersucht und es wird gezeigt, dass sein Einfluss noch bis zu 2200 m Entfernung zur Eiskante wirkt (für Meeresalbedo 0.042 und Meereisalbedo 0.91 bei 645 nm Wellenlänge) und von den makrophysikalischen Wolken- und Meereiseigenschaften abhängt. Die abgeleiteten Felder der optischen Dicke werden statistisch ausgewertet, um die Inhomogeneität der Wolken zu charakterisieren. Autokorrelationsfunktionen und Leistungsdichtespektren zeigen, dass Inhomogenitäten von Wolken mit vorranging richtungsabhängiger Struktur nicht mit einem allgemeingültigen Parameter beschrieben werden können. Es sind Inhomogenitätsmaße entlang und entgegen der jeweiligen Wolkenstrukturen nötig, um Fehler von bis zu 85% zu vermeiden.