Phase measurement Research Papers - Academia.edu (original) (raw)

2025, SPIE Proceedings

The Lick Observatory is pursuing new technologies for adaptive optics that will enable feasible low cost laser guidestar systems for visible wavelength astronomy. The Villages system, commissioned at the 40 inch Nickel Telescope this past Fall, serves as an on-sky testbed for new deformable mirror technology (high-actuator count MEMS devices), open-loop wavefront sensing and control, pyramid wavefront sensing, and laser uplink correction. We describe the goals of our experiments and present the early on-sky results of AO closed-loop and open-loop operation. We will also report on our plans for on-sky tests of the direct-phase measuring pyramid-lenslet wavefront sensor and plans for installing a laser guidestar system.

2025, Advanced Optical and Mechanical Technologies in Telescopes and Instrumentation

Visible Light Laser Guidestar Experiments (ViLLaGEs) is a new Micro-Electro Mechanical Systems (MEMS) based visible-wavelength adaptive optics (AO) testbed on the Nickel 1-meter telescope at Lick Observatory. Closed loop Natural Guide Star (NGS) experiments were successfully carried out during engineering during the fall of 2007. This is a major evolutionary step, signaling the movement of AO technologies into visible light with a MEMS mirror. With on-sky Strehls in I-band of greater than 20% during second light tests, the science possibilities have become evident. Described here is the advanced engineering used in the design and construction of the ViLLaGEs system, comparing it to the LickAO infrared system, and a discussion of Nickel dome infrastructural improvements necessary for this system. A significant portion of the engineering discussion revolves around the sizable effort that went towards eliminating flexure. Then, we detail upgrades to ViLLaGEs to make it a facility class instrument. These upgrades will focus on Nyquist sampling the diffraction limited point spread function during open loop operations, motorization and automation for technician level alignments, adding dithering capabilities and changes for near infrared science.

2025, Ultramicroscopy

The genesis, theoretical basis and practical application of the new electron holographic dark-field technique for mapping strain in nanostructures are presented. The development places geometric phase within a unified theoretical framework for phase measurements by electron holography. The total phase of the transmitted and diffracted beams is described as a sum of four contributions: crystalline, electrostatic, magnetic and geometric. Each contribution is outlined briefly and leads to the proposal to measure geometric phase by dark-field electron holography (DFEH). The experimental conditions, phase reconstruction and analysis are detailed for off-axis electron holography using examples from the field of semiconductors. A method for correcting for thickness variations will be proposed and demonstrated using the phase from the corresponding bright-field electron hologram.

2025

This paper describes a multipath estimation method for Global Positioning System (GPS) dual frequency carrier phase measurements. Multipath is a major error source in high precision GPS applications, i.e., carrier phase measurements for precise positioning and attitude determinations. In order to estimate and remove multipath at carrier phase measurements, an array GPS antenna system has been used. The known geometry

2025, Applied optics

We show by analytical and numerical calculations that the phase change on reflection that occurs in interference microscopy is almost independent of the numerical aperture of the objective. The shift of the microscope interferogram response due to the phase change on reflection, however, increases with the numerical aperture. Measurements of the interferogram shift are made with a Linnik interference microscope equipped with various numerical-aperture objectives and are reported and compared with theory.

2025, Maria Perera

Recent discussions in the scientific community have raised intriguing questions about nonphotosynthetic oxygen production in planetary environments. This study examines whether electrochemical "dark oxygen" production might theoretically occur on Mars through systematic analysis of electrical conductivity patterns, oxidized chemistry distributions, radar anomalies, and electromagnetic signatures. We present observational evidence potentially consistent with electrochemical processes, including correlations between: (1) electrical conductivity patterns and oxidized mineral distributions, (2) electromagnetic interference zones and chemical anomalies, (3) post-dust-storm chemical enhancements and electrical activity, and (4) planetary-scale redox patterns. While these observations suggest the possibility of electrochemical oxygen production on Mars, direct confirmation remains elusive and alternative explanations exist. If validated, such processes could represent a paradigm shift in understanding planetary habitability, where electromagnetic processes rather than stellar radiation might drive life-supporting chemistry.

2025, GPS Solutions

A tightly coupled filter integrating GPS and ultra-wideband (UWB) observations for high-precision position applications is implemented and tested to survey several external corner points of an eight story building. The filter uses GPS pseudoranges, GPS carrier-phase measurements, and UWB ranges and includes in-run estimation of UWB bias and scale factor states. The filter employs inequality constraints and innovation testing to mitigate the effects of unmodeled errors. The tightly coupled solution is compared to GPS-only, UWB-only, and loosely coupled solutions. The ability of each solution to detect measurement blunders is compared. Sub-meter level position solutions are maintained using tight-coupling in conditions where the solutions from the other three approaches are either unavailable or unreliable.

2025, Applied Optics

New applications for optical vortex interferometers (OVIs) are under investigation. The precision of the OVI depends strongly on the accuracy of positioning of the vortex points, which requires more than one interferogram (fringe pattern), so the influence of the laser beam's frequency stability is important. We present an analysis of the influence of the laser beam's frequency stabilization on the accuracy of methods locating vortex points relative to dimensions in optical arrangements of OVIs.

2025, Optics Letters

An array of pairs of parallel gold nanorods is shown to have a negative refractive index at the optical communication wavelength of 1.5 µm. This effect results from the plasmon resonance in the pairs of nanorods for both the electric and magnetic components of light. The refractive index is retrieved from the direct phase and amplitude measurements for transmission and reflection, which are all in excellent agreement with our finite difference time domain simulations. The refraction critically depends on the phase of the transmitted wave, which emphasizes the importance of phase measurements in finding n .

2025, GPS Solutions

This report provides a detailed performance analysis of three semicodeless dual-frequency GPS receivers for use in low Earth orbit (LEO). The test set comprises the Keywords Spaceborne GPS AE Semicodeless tracking AE IGOR AE OEM4-G2 AE... more

2025, Iranian Journal of Applied Physics

The use of heat-reflective glass has recently gained attention for its potential to reduce the electrical energy consumption required to cool buildings and mitigate electricity shortages. In this research, theoretical and experimental investigations of multi-layered coatings on glass, which is called spectrally selective glass, have been conducted. The aim was to prevent the entry of infrared thermal radiation and control radiation in the visible range. Using the theoretical method of multilayer thin film structures, the structure of three layers of zirconium dioxide/gold/zirconium dioxide has been simulated on glass and then made by the electron beam method. The simulations showed that this three-layer structure with a thickness of about 160 nm for ZrO2 and a gold coating thickness of about 20 nm is a proper choice. The sample made in the laboratory for this structure with a thickness of 160/20/160 nm matches well with the spectrum of the simulated samples and there is a slight deviation due to experimental error sources. The simulated and fabricated sample has more than 50% transmittance in the visible spectral range from 500 to 700 nm. There is a transmittance peak of more than 70% in the center of the visible range. The transmittance is less than 20% in the near-infrared spectrum range for the wavelength of 750 nm to 1100 nm. Therefore, this structure is very suitable for use as a reflector of infrared thermal radiation. This structure is a spectrally selective glass that can be used as a smart glass for radiant cooling purposes.

2025, IEEE Transactions on Geoscience and Remote Sensing

In this paper, an investigation of the potential of rapid refractivity retrieval is presented. The retrieval technique utilizes radar phase measurements of ground clutter to derive near-surface refractivity, which has been commonly used as a proxy for humidity, given its close relation to vapor pressure. Surface humidity is an important meteorological parameter and has been known to play an important role in convective initiation. In this paper, the refractivity retrieval technique is exploited by using smaller numbers of samples for phase calculation, which is a fundamental process in refractivity retrieval. The impetus for this paper is to explore the possibility of rapid refractivity retrieval by exploiting the rapid beam-steering capability of a phased-array radar. Using the National Weather Radar Testbed in Norman, OK, a 64-pulse per radial raw-data set was collected for conventional refractivity processing. Then, subsets of the 64 samples were extracted to emulate shorter dwell periods and the corresponding more rapid experiments. The test cases that were considered are 2, 4, 8, 16, and 32 samples. Refractivity fields retrieved using smaller numbers of samples are compared against the reference field, which was obtained using the entire 64-sample data set. It will be shown that, statistically, significant refractivity fields can be obtained from as short as a two-sample dwell.

2025

Optical Coherence Tomography (OCT) is a relatively new interferometric technology that allows for high-resolution and non-destructive tomographic imaging. One of its primary current uses is for in vivo and ex vivo examination of medical samples. It is used for non-destructive examination of ocular disease, dermatological examination, blood vessel imaging, and many other applications. Some primary advantages of OCT imaging include rapid imaging of biological tissue with minimal sample preparation, 3D high-resolution imaging with depth penetrations of several millimeters, and the capability to obtain results in real time, allowing for fast and minimally invasive identification of many diseases. Current commercial OCT systems rely heavily on optical fiber-based designs. They depend on the robustness of the fiber to maintain system performance in variable environmental conditions but sacrifice the performance and flexibility of free-space optical designs. We discuss the design and implementation of a free-space OCT interferometer that can automatically maintain its alignment, allowing for the use of a free-space optical design outside of tightly controlled laboratory environments. NIR Near Infrared. A range of light with a slightly longer wavelength than visible light. For optical components, this range often spans from about 650 nm to about 1000 nm . xvi * * @param x The number of pixels to shift horizontally by. * @param y The number of pixels to shift vertically by. * @throws AlignmentException If there is an error controlling the * motors. * @return Returns the number of motor counts moved by motor 1 and * motor 2. */

2025

2025, Optics Letters

We present a generic regularized formulation, based on robust half-quadratic regularization, for unwrapping noisy and discontinuous wrapped phase maps. Two cases are presented: the convex and the non-convex one. The unwrapped phase with the convex formulation is unique and robust to noise; however, the convex function solution is deteriorated by real discontinuities in phase maps; therefore, we also present a non-convex formulation which, with a parameter continuation strategy, shows a superior performance.

2025, Journal of the Optical Society of America A

Although one of the simplest and powerful approaches for the demodulation of a single fringe pattern with closed fringes is the regularized phase tracking (RPT) technique, this technique has two important drawbacks: its sensibility at the fringe-pattern modulation and the time employed in the estimation. In this paper we present modifications to the RPT technique which consist of the inclusion of a rough estimate of the fringe-pattern modulation, and the linearization of the fringe-pattern model which allow the minimization of the cost function through stable numerical linear techniques. With these changes, the demodulation of non-normalized fringe patterns is made with a significant reduction in the processing time, preserving the demodulation accuracy of the original RPT method.

2025, Metrologia

Two-way satellite time and frequency transfer (TWSTFT) is a primary technique for the generation of coordinated universal time (UTC). About 20 timing laboratories around the world continuously operate TWSTFT using satellite time and ranging equipment (SATRE 19 ) modems for remote time and frequency comparisons in this context. The precision of the SATRE TWSTFT as observed today is limited by an apparent daily variation pattern (diurnal) in the TWSTFT results. The observed peak-to-peak variation have been found as high as 2 ns in some cases. Investigations into the origins of the diurnals have so far provided no complete understanding about the cause of the diurnals. One major contributor to the diurnals, however, could be related to properties of the receive part in the modem. In 2014 and 2015, it was demonstrated that bypassing the receive part and the use of software-defined radio (SDR) Bureau International des Poids et Mesures 18 Author to whom any correspondence should be addressed. 19 Disclaimer: Commercial products are identified for the sake of technical clarity. No endorsement by the authors or their institutes are implied. We further caution the readers that none of the described equipment's apparent strengths or weaknesses may be characteristic of items currently marketed.

2025, IEEE Antennas and Propagation Magazine

The design of a system capable of making antenna gain and radiation pattern measurements at 2.4 GHz is presented. System performance based on component specifications is summarized and compared to measured data. Antenna measurements taken using the system are compared to those obtained using commercially available test equipment in an anechoic test chamber. The accuracy of the system is found to be ±0.5 dB within a dynamic range of 13 dB plus the gains of the antennas in use. The system is shown to be capable of making high quality antenna radiation pattern measurements in an anechoic test chamber. For a total cost of less than $1 300, the system presents an economical alternative to more sophisticated microwave measurement systems, and is well suited for use in a learning environment.

2025, Two-beam interferometry with a definitive phase-shift sign

Subject of study. The shift direction of interference fringes depending on the sign of the local phase shift introduced to one of the interfering waves was investigated in terms of two-beam interferometry. Aim of study. This study aimed to validate the fact that two-beam interferometry based on a single interferogram enables definitive determination of the phase-shift sign using the shift direction of the interference fringe. Method. Positions of the interference fringes and their shifts were calculated considering the phase distribution of interfering waves in the observation plane. The Mach-Zehnder interferometer was used to experimentally confirm the obtained theoretical results. Two closely adjacent substrates were used as objects. A subwavelength layer of a standard material was deposited on a part of the surface of one substrate, and a layer of metamaterial was deposited on the part of the second substrate. Main results. Expressions determining the direction and amplitude of the shift of interference fringes depending on the sign and amplitude of the local phase shift in one of the two interfering waves with a plane or spherical front were obtained. Strict rules of interference fringe shift depending on the sign of the phase shift were formulated based on the calculations. Results of the experiment using the Mach-Zehnder interferometer with different combinations of beams with spherical and plane wavefronts confirmed the theoretical calculations. Practical significance. Classic interferometric methods require significant time and the application of complex experimental procedures to determine the sign of the phase shift. The application of the results obtained in this study enables the determination of the sign of the introduced local phase shift based on a single interferogram without additional time expenditures. Thus, the method investigating the metamaterial layers of a subwavelength thickness is significantly simplified.

2025, PhDT

This thesis titled Snapshot Spectral Domain Optical Coherence Tomography prepared by Ashley Valdez has been submitted in partial fulfillment of requirements for a master's degree at the University of Arizona and is deposited in the... more

2025

1 , P. Lognonné 1 , W. B. Banerdt 2 , S. Deraucourt 1 , T. Gabsi 1 , J. Gagnepain-Beyneix 1 , T. Nébut 1 , O. Robert 1 , S. Tillier 1 , K. Hurst 2 , D. Mimoun 3 , U. Christenssen 4 , M. Bierwirth 4 , R. Roll 4 , T. Pike 8 , S. Calcutt 5 , D. Giardini 6 , D. Mance 6 , P. Zweifel 6 , P. Laudet 7 , L. Kerjean 7 , R. Perez 7 and the SEIS Team 1 . (1) IPGP-Sorbonne Paris Cité, Univ Paris, France Diderot, (2) JPL (Jet Propulsion Laboratory), USA, (3) ISAE, Université de Toulouse, France, (4) MPS, Germany, (5) Oxford U, UK, (6) ETHZ, CH, (7) CNES, France, (8) Imperial collegue, UK.

2025, Current Biology

light-dark schedule (Figure ). Phase shifts were measured on days 3 and 6 in DD following the phase advance in the light-dark schedule (Figure ). The peak times of Per1-luc bioluminescence were advanced by 3.9 Ϯ 0.7 hr (day 3, n ϭ 6) and... more

2025, Optics Letters

We demonstrate an optical scheme for measuring the thickness of thin nanolayers with the use of light beam's spatial modes. The novelty in our scheme is the projection of the beam reflected by the sample onto a properly tailored spatial mode. In the experiment described below, we are able to measure a step height smaller than 10 nm, i.e., oneeightieth (1∕80) of the wavelength with a standard error in the picometer scale. Since our scheme enhances the signal-to-noise ratio, which effectively increases the sensitivity of detection, the extension of this technique to the detection of subnanometric layer thicknesses is feasible.

2025, Proceedings of SPIE

Keck Interferometer is a NASA-funded project to combine the two 10 m Keck telescopes for high sensitivity nearinfrared fringe visibility measurements, nulling interferometry at 10 µm to measure the quantity of exozodiacal emission around nearby stars, and differential-phase measurements to detect "hot-Jupiters" by their direct emission. It is being developed by the Jet Propulsion Laboratory, the W. M. Keck Observatory, and the Michelson Science Center. Recent activity has included formal visibility mode commissioning, as well as science observations, and we briefly review some of the significant technical aspects and updates to the system. We have also completed laboratory development of the nuller. The nuller uses two modified Mach-Zehnder input nullers, a Michelson cross combiner, and a 10 µm array camera to produce background-limited null measurements. To provide required temporal stability for the nuller, the system incorporates end-to-end laser metrology with phase referencing from two 2.2 µm fringe trackers. The nuller recently completed its pre-ship review and is being installed on the summit. After nuller integration and test, the differential phase mode will be deployed, which will use a 2-5 µm fringe detector in combination with a precision path length modulator and a vacuum delay line for dispersion control.

2025

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2025, Advanced Wavefront Control: Methods, Devices, and Applications VIII

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2025, Environmental and Experimental Botany

Many plant species are able to grow at very high carbon dioxide (CO 2 ) concentrations at the sites of the natural geothermal CO 2 enrichment (natural CO 2 springs). It is to expect that in such an environment the increased concentrations of soil CO 2 could directly affect root function, e.g. respiration, which could be of crucial importance for plant performance. In our study, root respiration of different grasses growing at the natural carbon dioxide spring Stavešinci (NE, Slovenia) was studied. By using liquid phase measurements (Clark-type oxygen electrodes) and potassium hydrogencarbonate addition, high concentrations of dissolved inorganic carbon species were obtained in the system, leading to high concentrations of soluble CO 2 (CO 2(aq) ), thus simulating a high CO 2 environment. For all species measured (Alopecurus pratensis L., Dactylis glomerata L., Echinochloa crus-galli (L.) PB., Holcus lanatus L., Phleum pratense L., Poa pratensis L. and Setaria pumila (Poir.) Roem. & Schult.) a relatively low sensitivity of root respiration to increased CO 2(aq) was observed. A significant inhibition (ranging from 16 to 54%) was measured at 8.3 mM CO 2(aq) in the assay buffer solution. When root respiration of plants from different CO 2 exposures, i.e. locations at the mofette, was compared at ambient CO 2 concentration, no consistent differences were observed.

2025, Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films

We studied the growth of silicon films deposited by hot-wire chemical vapor deposition under different values of filament current, substrate temperature, and hydrogen dilution ratio. The physical and electrical properties of the films were studied by Raman spectroscopy, x-ray diffraction, atomic force microscopy, conductive-atomic force microscopy, and transmission electron microscopy. There is an interdependence of the growth parameters, and films grown with different parameters can have similar structures. We discuss why this interdependence occurs and how it influences the properties of the deposited films, as well as the deposition rate. In general, the films have a complex structure, with a mixture of amorphous, (220)-oriented crystalline and nanocrystalline phases present in most cases. The amount of each phase can be controlled by the variation of one or more of the growth parameters at a time.

2025, Environmental Chemistry

Environmental context. Gaseous organic compounds fuel the production of ozone in the background lower atmosphere. There have been no measurements of many of these compounds in the temperate and polar latitudes of the Southern Hemisphere. Here some first results are presented that show in general much lower concentrations than the Northern Hemisphere, due in part to the lower land surfaces and biomass burning in the Southern Hemisphere. . Measurements were made of volatile organic compounds (VOCs) at Cape Grim using proton transfer reaction mass spectrometry (PTR-MS) during the Precursors to Particles (P2P) Campaign from 10 February to 1 March 2006. Approximately 14 days of clean air data were obtained along with 4 days of data from when polluted air, first from a smoke plume from a fire on Robbins Island adjacent to the station and then air from Victoria, was present. This paper deals with the results obtained in clean air, the focus of the P2P campaign. The protonated masses and pr...

2025, Proceedings of the DIPAC09 Switzerland

The two-beam acceleration scheme foreseen for CLIC and the associated radio-frequency (RF) components will be tested in the Two-beam Test Stand (TBTS) at CTF3, CERN. Of special interest is the performance of the power extraction structures (PETS) and the acceleration structures as well as the stability of the beams in the respective structures. After the recent completion of the TBTS, the first 12 GHz PETS has been tested with beam, using so-called recirculation of the RF power inside the PETS. The TBTS allows precise ...

2025, SPIE Proceedings

A Cassegrain mounted adaptive optics instrument presents unique challenges for opto-mechanical design. The flexure and temperature tolerances for stability are tighter than those of seeing limited instruments. This criteria requires particular attention to material properties and mounting techniques. This paper addresses the mechanical designs developed to meet the optical functional requirements. One of the key considerations was to have gravitational deformations, which vary with telescope orientation, stay within the optical error budget, or ensure that we can compensate with a steering mirror by maintaining predictable elastic behavior. Here we look at several cases where deformation is predicted with finite element analysis and Hertzian deformation analysis and also tested. Techniques used to address thermal deformation compensation without the use of low CTE materials will also be discussed.

2025, SPIE Proceedings

The Lick Observatory's Shane 3-meter telescope has been upgraded with a new infrared instrument (ShARCS -Shane Adaptive optics infraRed Camera and Spectrograph) and dual-deformable mirror adaptive optics (AO) system (ShaneAO). We present first-light measurements of imaging sensitivity in the Ks band. We compare measured results to predicted signal-to-noise ratio and magnitude limits from modeling the emissivity and throughput of ShaneAO and ShARCS. The model was validated by comparing its results to the Keck telescope adaptive optics system model and then by estimating the sky background and limiting magnitudes for IRCAL, the previous infra-red detector on the Shane telescope, and comparing to measured, published results. We predict that the ShaneAO system will measure lower sky backgrounds and achieve 20% higher throughput across the JHK bands despite having more optical surfaces than the current system. It will enable imaging of fainter objects (by 1-2 magnitudes) and will be faster to reach a fiducial signal-to-noise ratio by a factor of 10-13. We highlight the improvements in performance over the previous AO system and its camera, IRCAL.

2025, Optical Engineering

A real-time visual approach for the calibration of phase step in image plane holography using BaTiO 3 crystal as a recording medium is reported. In this method, the diffuse object is illuminated symmetrically with two collimated beams and a pump beam is added at the crystal plane. Each illuminating beam generates an individual interferogram at the observation plane when the object is subjected to load. A phase shift to one of the illuminating beams results in the complete disappearance of the fringes due to phase reversal between the individual interferograms, and at 2 phase change, the fringe pattern is restored. After calibration, a single-beam illumination configuration is used for phase measurement. We present the theory of the method and experimental results for a centrally loaded diaphragm rigidly clamped along the periphery.

2024, AIP Conference Proceedings

Both relativistic and nonrelativistic magnetrons are under experimental and theoretical investigation at U of M. Relativistic (Titan-6-vane) magnetron experiments (300-400 kV, 1-10 kA, 0.5 microsecond) investigate mode control with various output coupling geometries. Mode competition between the pi mode and the 2/3 pi mode has been characterized for two-versus-three output extractors for comparison with particle in cell simulations. Phase measurements and timefrequency-analysis are performed for mode identification. Peak microwave output power on the order 0.5 GW has been measured, assuming equal output from 3 waveguides. Nonrelativistic (4 kV, <1A, kW microwave power) magnetron experiments are performed on commercial oven magnetrons for an in-depth investigation of crossed-field injection-locking and noise. Injection-locking is demonstrated by utilizing an oven magnetron as a reflection amplifier. Noise generation is explored as a function of injected signal and cathode conditions.

2024, Japanese Journal of Applied Physics

2024, Physica A: Statistical Mechanics and its Applications

The use of Mean-Field theory to unwrap principal phase patterns has been recently proposed. In this paper we generalize the Mean-Field approach to process phase patterns with arbitrary degree of undersampling. The phase unwrapping problem is formulated as that of finding the ground state of a locally constrained, finite size, spin-L Ising model under a non-uniform magnetic field. The optimization problem is solved by the Mean-Field Annealing technique. Synthetic experiments show the effectiveness of the proposed algorithm.

2024

We employ quantum state discrimination theory to establish the ultimate limit for spoofing detection in electromagnetic signals encoded with random quantum states. Our analysis yields an analytical expression for the optimal bound, which we prove can be achieved using a pair of coherent states. Notably, the quantum enhancement persists regardless of photon number, thereby removing the previous constraint to single-photon sources. This breakthrough unlocks new experimental possibilities using standard laser sources. Furthermore, we explore the encoding of squeezed states and demonstrate that the detection probability approaches 100% when the spoofer's capability is restricted to coherent-state generation.

2024, IEEE Transactions on Consumer Electronics

Driven by the expanding demand of location based services (LBS), the integration of satellite navigation receiver into mobile devices has received much attention in the last years. Snapshot positioning technique has turned out to be a very suitable candidate in LBS applications for its predominance of low cost and low power dissipation. However, the limited snapshot length is a major hurdle that limits the availability and accuracy of receivers. A code phase measurement technique is developed and used for snapshot receivers. By utilizing the features of the modernized global navigation satellite system (GNSS) signals and the characteristic of snapshot positioning, it uses a novel dual update-rate tracking loop with a non-causal smoothing estimator to obtain a relatively accurate estimation from a second or less snapshot data. Experiments with simulated data show that the proposed method has better estimation accuracy than the conventional code tracking loop in confined data length snapshot receivers 1 .

2024, Chemical Physics Letters

A computational approach is presented for prediction and interpretation of core-level spectra of complex molecules. Applications are presented for several isolated organic molecules, sampling a range of chemical bonding and structural motifs. Comparison with gas phase measurements indicate that spectral lineshapes are accurately reproduced both above and below the ionization potential, without resort to ad hoc broadening. Agreement with experiment is significantly improved upon inclusion of vibrations via molecular dynamics sampling. We isolate and characterize spectral features due to particular electronic transitions enabled by vibrations, noting that even zero-point motion is sufficient in some cases.

2024, Mediterranean Microwave Symposium

This work describes how indirect holography which has previously been applied to the determination of antenna radiation patterns can be adapted for the imaging of passive objects. It provides details of how complex scattered field values can be obtained in a simple and inexpensive manner from sampled scalar intensity measurements taken over a single scanning aperture. This work uses indirect holographic techniques to image a number of simple objects including a rectangular metallic plate, a small metal plate covered by a dielectric sheet and a small metallic circular annulus. This work demonstrates that good quality images can be reconstructed from simple scalar intensity patterns. It demonstrates that clear outlines can be obtained in particular from reconstructed phase patterns and that good images can be obtained from objects with dimensions of the order of a half wavelength.

2024

Smaller objects reconstruction using three dimensional techniques is one among the challenged tasks from the decade. Researchers in graphical designing and professionals of photography are continuously working on the reconstruction of 3D object techniques to meet the demand of real time applications of almost all in every walk of real life. Reconstruction of 3D objects has a major role in the reverse engineering applications too. The major challenges in successful 3D object reconstruction are high computational costs and lack of accuracy. Fringe projection has come into view as a propitious 3D reconstruction mechanism with low computational cost for high precision and resolutions. It makes use of Digital projection, structured light systems and phase analysis on fringed images. Its performance is shown as acceptable in the research analysis carried out on the implementation of it and its insensitiveness to ambient light. An overview of some of the fringe projection techniques are presented in this paper and also propose a new simple fringe projection system which can yield the more accurate and acceptable results with different objects.

2024

This thesis concerns the development of simple, compact scanning optical microscopes which can obtain confocal and interference images. The effects of feeding the reflected signal back into the laser cavity of a confocal microscope are investigated and exploited. Monomode optical fibres are used to perform the spatial filtering required for confocal microscopy and, later, as the source of reference beams for interferometry. The theory describing the basic operation of the microscopes is developed. The optical systems are modelled using scalar diffraction theory and the effects of optical feedback into the laser cavity are described, with the practical implications emphasised. A fully reciprocal arrangement of the microscope is developed, in which a single mode optical fibre both launches the signal towards the object and then collects the reflected signal. The fibre is shown to exhibit the spatial filtering properties required for the source and detector in a confocal microscope. ...

2024, Optics and Photonics Society of Iran

We analytically investigate distributed circuit modeling of the tunable-enhanced Goos-Hänchen shift of light beams from a Graphene containing structure which supports TM surface waves. Here the coupling of the incident wave to the surface modes of the structure is used to enhance the Goos-Hänchen shift of the totally reflected wave. It is also shown that this large lateral shift can be controlled trough controlling the dispersion properties of the surface modes by applying an electrical voltage to the Graphene layer. A distributed circuit model is proposed for the Graphene containing structure and used to calculate the reflection coefficient of the structure. Phase of the reflection coefficient is then used to calculate the Goos-Hänchen shift. Our calculations show that by coupling the incident wave to the surface modes of the structure large Goos-Hänchen shift as high as 100 times of the free space wavelength can be achieved. Furthermore this large shift can be tuned by apply relat...

2024, Physical Review A

We perform a quantum theoretical calculation of the noise power spectrum for a phase measurement of the light output from a coherently driven optical cavity with a freely moving rear mirror. We examine how the noise resulting from the quantum back action appears among the various contributions from other noise sources. We do not assume an ideal (homodyne) phase measurement, but rather consider phase modulation detection, which we show has a different shot noise level. We also take into account the effects of thermal damping of the mirror, losses within the cavity, and classical laser noise. We relate our theoretical results to experimental parameters, so as to make direct comparisons with current experiments simple. We also show that in this situation, the standard Brownian motion master equation is inadequate for describing the thermal damping of the mirror, as it produces a spurious term in the steady-state phase fluctuation spectrum. The corrected Brownian motion master equation [L.

2024, Sensors and Actuators B: Chemical

The object of the present paper is to report on new versions of the difference interferometer which have been sucessfully used for refractometric measurements and for humidity-and biosensing, i.e., for real-time monitoring of the adsorption of proteins and of affinity-and immunoreactions. The basic principle of the difference interferometers is as follows: the TE,, and TM, modes in a planar (or rib) waveguide are coherently excited and propagate on a common path and interact with the sample. The polarization-dependent interaction induces a timedependent phase difference A (t)betweentheTE,,andTM0modes,whichismeasuredastheinterferometer′sresponse.WehavedevelopeddifferentmethodstomeasurethephasedifferenceA( t) between the TE,, and TM0 modes, which is measured as the interferometer's response. We have developed different methods to measure the phase difference A(t)betweentheTE,,andTM0modes,whichismeasuredastheinterferometer′sresponse.WehavedevelopeddifferentmethodstomeasurethephasedifferenceA( t) . The new methods have some advantages and can be expected to be easily extendable to multichannel (multianalyte) sensing. In the reported experiments we use not only SiOZ-TiO:, but also S&N4 films as high-refractive-index waveguides on oxidized silicon wafers as substrates.

2024, Journal of Microbiological Methods

Fourier-transform infrared (FT-IR) spectroscopy is known as a high-resolution method for the rapid identification of pure cultures of microorganisms. Here, we evaluated FT-IR as a method for the quantification of bacterial populations in binary mixed cultures consisting of Pseudomonas putida and Rhodococcus ruber. A calibration procedure based on Principal Component Regression was developed for estimating the ratio of the bacterial species. Data for method calibration were gained from pure cultures and artificially assembled communities of known ratios of the two member populations. Moreover, to account for physiological variability, FT-IR measurements were performed with organisms sampled at different growth phases. Measurements and data analyses were subsequently applied to growing mixed cultures revealing that growth of R. ruber was almost completely suppressed in co-culture with P. putida. Population ratios obtained by fatty acid analysis as an independent reference method were in high agreement with the FT-IR derived ratios.

2024

High order adaptive optics at high speed (1kHz), high accuracy (10 cm) and high photon efficiency requirements is needed for high contrast imaging in the infrared for exo-planet detection. An AO system with conventional deformable mirrors and reconstruction from slope measurements would be expensive and extremely difficult to produce. In this paper we describe a "reconstructorfree" high order adaptive optics system using a self-referenced Mach-Zehnder wavefront sensor and a liquid crystal phase corrector. Phase measurements are obtained directly from the two outputs the Mach-Zehnder interferometer, with ±λ/4 pathlength difference between its two legs. The intensity difference between corresponding pixels on the two cameras outputs is proportional to phase error, provided this is small, and correction takes place at the pixel level with a liquid crystal phase corrector whose square geometry matches the wavefront sensor camera pixels. In this way high resolution and photon efficiency are achieved in a system with direct, pixel-based estimation, control and correction of phase error. We have achieved in the laboratory wavefront retrieval with very fine scale sampling (128 phase measurements across the aperture) with λ/30 rms accuracy. Although the current electronics lacks dynamic range and speed, these could be readily improved for a real telescope system. Very recent progresses in decreasing the fall time of liquid crystal using the dual frequency method will allow for correction at kHz rates. While limited to correction of small wavefront amplitude errors (≤ 1 wave), such a system could be used very efficiently in tandem with a lower order system of high dynamic range.

2024, OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information)

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2024, Journal of the Optical Society of America

The advent of interferometric synthetic aperature radar for geophysical studies has resulted in the need for accurate, efficient methods of two-dimensional phase unwrapping. Inference of the lost integral number of cycles in phase measurements is critical for three-pass surface deformation studies as well as topographic mapping and can result in an order of magnitude increase in sensitivity for two-pass deformation analysis. While phase unwrapping algorithms have proliferated over the past ten years, two main approaches are currently in use. Each is most useful only for certain restricted applications. All these algorithms begin with the measured gradient of the phase field, which is subsequently integrated to recover the unwrapped phases. The earliest approaches in interferometric applications incorporated residue identification and cuts to limit the possible integration paths, while a second class using least-squares techniques was developed in the early 1990's. We compare the approaches and find that the residue-cut algorithms are quite accurate but do not produce estimates in regions of moderate phase noise. The least-squares methods yield complete coverage but at the cost of distortion in the recovered phase field. A new synthesis approach, combining the cuts from the first class with a least-squares solution, offers greater spatial coverage with less distortion in many instances.