Search NASA⌕ Search

SEARCH · Search NASA

Results for “optical interference”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Gravitizing the quantum

We discuss a new approach to the problem of quantum gravity in which the quantum mechanical structures that are traditionally fixed, such as the Fubini–Study metric in the Hilbert space of states, become dynamical and so implement the idea of gravitizing the quantum. In particular, in this formulation of quantum gravity the quantum geometry is still consistent with the principles of unitarity and also captures fundamental aspects of (quantum) gravity, such as topology change. As a result, we address specific ways of testing this new approach to quantum gravity by utilizing multipath interference and optical lattice atomic clocks.

Quantum gravity↗
DOE OSTI2022

Gradient Field Detection Using Interference of Stimulated Microwave Optical Sidebands

Here, we demonstrate that stimulated microwave optical sideband generation using parametric frequency conversion can be utilized as a powerful technique for coherent state detection in atomic physics experiments. The technique has advantages over traditional absorption or polarization rotation-based measurements and enables the isolation of signal photons from probe photons. We outline a theoretical framework that accurately models sideband generation using a density matrix formalism. Using this technique, we demonstrate a novel intrinsic magnetic gradiometer that detects magnetic gradient fields between two spatially separated vapor cells by measuring the frequency of the beat note between sidebands generated within each cell. The sidebands are produced with high efficiency using parametric frequency conversion of a probe beam interacting with 87 Rb atoms in a coherent superposition of magnetically sensitive hyperfine ground states. Interference between the sidebands generates a low-frequency beat note whose frequency is determined by the magnetic field gradient between the two vapor cells. In contrast to traditional gradiometers the intermediate step of measuring the magnetic field experienced by the two vapor cells is unnecessary. We show that this technique can be readily implemented in a practical device by demonstrating a compact magnetic gradiometer sensor head with a sensitivity of 25 fT/cm/ √ Hz with a 4.4 cm baseline, while operating in a noisy laboratory environment unshielded from Earth’s field.

74 ATOMIC AND MOLECULAR PHYSICS↗
NASA NTRS2009

Exploring Divisibility and Summability of 'Photon' Wave Packets in Nonlinear Optical Phenomena

Formulations for second and higher harmonic frequency up and down conversions, as well as multi photon processes directly assume summability and divisibility of photons. Quantum mechanical (QM) interpretations are completely congruent with these assumptions. However, for linear optical phenomena (interference, diffraction, refraction, material dispersion, spectral dispersion, etc.), we have a profound dichotomy. Most optical engineers innovate and analyze all optical instruments by propagating pure classical electromagnetic (EM) fields using Maxwell s equations and gives only lip-service to the concept "indivisible light quanta". Further, irrespective of linearity or nonlinearity of the phenomena, the final results are always registered through some photo-electric or photo-chemical effects. This is mathematically well modeled by a quadratic action (energy absorption) relation. Since QM does not preclude divisibility or summability of photons in nonlinear & multi-photon effects, it cannot have any foundational reason against these same possibilities in linear optical phenomena. It implies that we must carefully revisit the fundamental roots behind all light-matter interaction processes and understand the common origin of "graininess" and "discreteness" of light energy.

Prasad, Narasimha↗
DOE OSTI2023

Mass of a weakly measured photon

Bohmian mechanics has garnered significant attention as an interpretation of quantum theory since the paradigmatic experiments which inferred the average trajectories of photons in the nonrelativistic regime. These experiments were largely motivated by Wiseman's formulation of Bohmian mechanics, which grounded these trajectories in weak measurements. Recently, Wiseman's framework was extended to the relativistic regime by expressing the velocity field of single photons in terms of weak values of the photon energy and momentum. Here, we propose an operational, weak value-based definition for the Bohmian “local mass” of relativistic single particles. For relativistic wave functions satisfying the scalar Klein-Gordon equation, this mass coincides with the effective mass defined by de Broglie in his relativistic pilot-wave theory, a quantity closely connected with the quantum potential that is responsible for Bohmian trajectory self-bending and the anomalous photoelectric effect. Here, we demonstrate the relationship between the photon trajectories and the mass in an interferometric setup.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS1993

Simple in-line method to measure the dispersion of an optical system

We describe a simple in-line method to measure the dispersion of an optical system. The light beam passing through the optical system interferes with a reference beam in a spectrometer, and the resulting spectrum yields the quadratic and cubic dispersion terms of the system. We demonstrate this technique on an optical system made of grating pairs.

Yao, X. S.↗
NASA NTRS1988

Fiber optic sensor technology - An opportunity for smart aerospace structures

Fiber optic sensors provide the opportunity for fabricating materials with internal sensors which can serve as lifetime health monitors, analogous to a central nervous system. The embedded fiber optic sensors can be interrogated by various techniques to measure internal strain, temperature, pressure, acoustic waves and other parameters indicative of structural integrity. Experiments have been conducted with composite samples with embedded sensors to measure strain using optical time domain reflectometry, modal interference and an optical phase locked loop. Fiber optic sensors have been developed to detect acoustic emission and impact damage and have been demonstrated for cure monitoring. These sensors have the potential for lifetime monitoring of structural properties, providing real time nondestructive evaluation.

Heyman, J. S.↗
NASA NTRS2002

Vapor transport growth of organic solids in microgravity and unit gravity: some comparisons and results to date

Thin films of an organic nonlinear optical (NLO) material, N, N-dimethyl-p-(2,2-dicyanovinyl) aniline (DCVA), have been grown in space and on the ground by physical vapor transport in an effusive ampoule arrangement. The thin film growth technique developed on the ground is a direct result of information gleaned from experiments in microgravity. This paper covers the results of our experimental investigations for establishing "ideal" terrestrial conditions for deposition of a DCVA film. The active control during the deposition process was exercised by three deposition variables: the material source temperature, the background pressure external to the growth ampoule and the substrate temperature. Successful growth occurred when the difference in temperature between the source material and the copper substrate was 14 degrees C and the background nitrogen pressure was such that the transport was either diffusive or convective. A qualitative diffusion limited boundary was estimated to occur at a pressure of approximately 20 torr. We have probed the DCVA thin films with visible-near infrared reflection absorption spectroscopy, polarized Fourier transform infrared spectrometry, differential interference contrast optical microscopy, and stylus profilometry.

short duration↗
DOE OSTI2019

Precision loss measurements in short lengths of optical fibre by reflectometry without using Rayleigh scattering

To improve accuracy of light attenuation measurements in optical fibres, especially in short ones, tens and hundreds of metres in length, we propose rejecting a conventional reflectometric approach based on Rayleigh scattering intensity measurements. To this end, we propose for the first time the use of boson peaks in Raman scattering, which, on the one hand, produce no interference effects and no related noise in reflectograms, and, on the other, lie within the C-band. Even at a fibre length as short as 50 m, the attenuation measurement error does not exceed 0.002 dB km{sup −1}. We demonstrate the possibility of compensating for the temperature variation of boson peak intensity by concurrently obtaining a reflectogram for the anti-Stokes line of the fundamental Raman band. (paper)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS2006

Improved Oxygen-Beam Texturing of Glucose-Monitoring Optics

An improved method has been devised for using directed, hyperthermal beams of oxygen atoms and ions to impart desired textures to the tips of polymethylmethacrylate [PMMA] optical fibers to be used in monitoring the glucose content of blood. The improved method incorporates, but goes beyond, the method described in Texturing Blood-Glucose- Monitoring Optics Using Oxygen Beams (LEW-17642-1), NASA Tech Briefs, Vol. 29, No. 4 (April 2005), page 11a. The basic principle of operation of such a glucose-monitoring sensor is as follows: The textured surface of the optical fiber is coated with chemicals that interact with glucose in such a manner as to change the reflectance of the surface. Light is sent down the optical fiber and is reflected from, the textured surface. The resulting change in reflectance of the light is measured as an indication of the concentration of glucose. The required texture on the ends of the optical fibers is a landscape of microscopic cones or pillars having high aspect ratios (microscopic structures being taller than they are wide). The average distance between hills must be no more than about 5 mso that blood cells (which are wider) cannot enter the valleys between the hills, where they would interfere with optical sensing of glucose in the blood plasma. On the other hand, the plasma is required to enter the valleys, and high aspect ratio structures are needed to maximize the surface area in contact with the plasma, thereby making it possible to obtain a given level of optical glucose-measurement sensitivity with a relatively small volume of blood. There is an additional requirement that the hills be wide enough that a sufficient amount of light can propagate into them and, after reflection, can propagate out of them. The method described in the cited prior article produces a texture comprising cones and pillars that conform to the average-distance and aspect-ratio requirements. However, a significant fraction of the cones and pillars are so narrow that not enough light can propagate along them. The improved method makes it possible to form wider cones and pillars while still satisfying the average-distance and aspect-ratio requirements. In the improved method, as in the previously reported method, multiple optical fibers are first bundled together for simultaneous texturing of their distal tips. However, prior to texturing by exposure to an oxygen beam, the tips are first coated by vapor deposition of a thin, sparse layer of aluminum: The exposure to the aluminum vapor must be short enough (typically of the order of seconds) so that the aluminum nucleates into islands separated by uncoated areas. The coated tips are textured by exposure to a directed beam of hyperthermal (kinetic energy >1 eV) oxygen atoms and/or ions in a vacuum chamber, as in the previously reported method. The aluminum islands partially shield the underlying PMMA from oxidation and erosion by the beam, so that the cones or pillars remaining after texturing are wider than they would otherwise be. To some extent, the dimensions of the hills and the distances between them can be tailored through choice of the thickness of the aluminum coat and/or the oxygen-beam fluence. The figure illustrates an example of texturing of the tip of a PMMA optical fiber without and with prior aluminum coating.

Banks, Bruce A.↗
NASA NTRS2013

Miniature Sensor Probe for O2, CO2, and H2O Monitoring in Portable Life Support Systems

A miniature sensor probe, composed of four sensors which monitor the partial pressure of O2, CO2, H2O, and temperature, designed to operate in the portable life support system (PLSS), has been demonstrated. The probe provides an important advantage over existing technology in that it is able to operate reliably while wet. These luminescence-based fiber optic sensors consist of an indicator chemistry immobilized in a polymeric film, whose emission lifetime undergoes a strong change upon a reversible interaction with the target gas. Each sensor includes chemistry specifically sensitive to one target parameter. All four sensors are based on indicator chemistries that include luminescent dyes from the same chemical family, and therefore exhibit similar photochemical properties, which allow performing measurements of all the sensors by a single, compact, low-power optoelectronic unit remotely connected to the sensors by an electromagnetic interference-proof optical fiber cable. For space systems, using these miniature sensor elements with remote optoelectronics provides unmatched design flexibility for measurements in highly constrained volume systems such as the PLSS. A 10 mm diameter and 15 mm length prototype multiparameter probe was designed, fabricated, tested, and demonstrated over a wide operational range of gas concentration, humidity, and temperature relevant to operation in the PLSS. The sensors were evaluated for measurement range, precision, accuracy, and response time in temperatures ranging from 50 aF-150 aF and relative humidity from dry to 100% RH. Operation of the sensors in water condensation conditions was demonstrated wherein the sensors not only tolerated liquid water but actually operated while wet.

Delgado, Jesus↗
NASA NTRS1987

A near-earth optical communications terminal with a corevolving planetary sun shield

The umbra of a planet may serve as a sun shield for a space based optical communications terminal or for a space based astronomical observatory. An orbit that keeps the terminal or observatory within the umbra is desirable. There is a corevolution point behind every planet. A small body stabilized at the planet corevolution point will revolve about the sun at the same angular velocity as the planet, always keeping the planet between itself and the sun. This corevolution point is within the umbra of Mars but beyond the end of the umbra for Mercury, Venus, and earth. The Mars corevolution point is an ideal location for an astronomical observatory. There Mars obstruct less than 0.00024 percent of the sky at any time, and it shades the observatory completely from the sun. At the earth corevolution point, between 51 and 84 percent of the solar disk area is blocked, as is up to 92 percent of the sunlight. This provides a reduction from 3 dB to 11 dB in sunlight that could interfere with optical communications if scattered directly into the detectors. The variations is caused by revolution of the earth about the earth-moon barycenter.

Kerr, E. L.↗
NASA NTRS1989

A near-earth optical communications terminal with a corevolving planetary sun shield

The umbra of a planet may serve as a sun shield for a space-based optical communications terminal or for a space-based astronomical observatory. An orbit that keeps the terminal or observatory within the umbra is desirable. There is a corevolution point behind every planet. A small body stabilized at the planet corevolution point will revolve about the sun at the same angular velocity as the planet, always keeping the planet between itself and the sun. This corevolution point is within the umbra of Mars but beyond the end of the umbra for Mercury, Venus, and earth. The Mars corevolution point is an ideal location for an astronomical observatory. There, Mars obstruct less than 0.00024 percent of the sky at any time, and it shades the observatory completely from the sun. At the earth corevolution point, between 51 and 84 percent of the solar disk area is blocked, as is up to 92 percent of the sunlight. This provides a reduction from 3 dB to 11 dB in sunlight that could interfere with optical communications if scattered directly into the detectors. The variations is caused by revolution of the earth about the earth-moon barycenter.

Kerr, E. L.↗
NASA NTRSDate not supplied

The Lunar Explorer Instrument for Space Biology Applications (LEIA) Pre-Flight Tests: Mechanical Considerations​

The BioSensor payload on the upcoming LEIA platform aboard the CLPS (CP-22) lander will carry yeast to the Moon's south pole to study the effects of lunar radiation and gravity. From Earth, BioSensor will transport desiccated yeast within 16 fluidic cards, each containing 16 fluidic wells of 100 microliters volume. At the start of the experiment, these microbes will be autonomously rehydrated on the Moon, and optical absorbance measurements at three wavelengths will be performed across all 256 wells. Absorbance measurements in fluidic wells are susceptible to noise and artifacts due to bubble formation during well rehydration and microbial growth. BioSensor, as a biofluidics system, faces significant data anomalies caused by payload vibrations, particularly from the operation of the co-located PROSPECT’s ProSEED drill, to assess lunar resources by penetrating the subsurface. To evaluate the impact of drill vibrations, fully assembled and filled fluidic cards were subjected to sine sweep signals in the x, y, z planes, ranging from 5 - 2560 Hz at g-loads of 0.25 and 0.5, with on-board accelerometer for localized vibration measurement. Wells with various fill conditions, including partial fills with different bubble sizes and completely filled wells, were tested. Results indicated that small bubbles adhered to well walls at high frequencies but were dislodged at low frequencies, causing data anomalies. Medium and large bubbles exhibited higher interference with optical data due to lower surface tension and variable bubble surface flexion. Overall, it was found that irrespective of the fill type, low-frequency vibrations were most detrimental to optical readings. Understanding the drill schedule and correlating it with BioSensor timestamps will help identify periods when BioSensor data is unreliable, a crucial step for accurately interpreting the microbial response data and ensuring the validity of the BioSensor's scientific measurements on the lunar surface.

Chinmayee Govinda Raj↗
DOE OSTI2019

Comparative performance analysis of relative humidity sensor based on intermodal interference using tapered square no-core optical fiber and tapered cylindrical optical fiber

This work presents the computational evaluation of a new model for relative humidity sensor based on the principle of intermodal interference using a square-section no-core tapered optical fiber compared to a classical cylindrical tapered optical fiber sensor. Attempting at a new application of this type of sensor, simulations were carried out in the range of up to 60% of relative humidity, the main interest range of the pharmaceutical industry. Several materials were used in its modeling and an analysis was developed in its constructive dimensions, in order to verify the influence of each of them on the sensor performance.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

Realization of spin wave switch for data processing

In this work, experimental data on a spin wave switch based on spin wave interference is reported. The switch is a three terminal device where spin wave propagation between the source and the drain is modulated by the control spin wave signal. The prototype is a micrometer scale device based on Y 3 Fe 2 (FeO 4 ) 3 film. The output characteristics show the oscillation of the output spin wave signal as a function of the phase difference between the source and the drain spin wave signals. The On/Off ratio of the prototype exceeds 20 dB at room temperature. The utilization of phase in addition to amplitude for information encoding offers an innovative route towards multi-state logic circuits. The advantages and shortcomings of spin wave switches are also discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Assembly of Building Blocks by Double-End-Anchored Polymers in the Dilute Regime Mediated by Hydrophobic Interactions at Controlled Distances

Hierarchical assembly of building blocks via competing, orthogonal interactions is a hallmark of many of nature’s composite materials that do not require highly specific ligand-receptor interactions. To mimic this assembly mechanism requires the development of building blocks capable of tunable interactions. In the present work, we explored the interplay between repulsive (steric and electrostatic) and attractive hydrophobic forces. The designed building blocks allow hydrophobic forces to effectively act at controlled, large distances, to create and tune the assembly of membrane-based building blocks under dilute conditions and affect their interactions with cellular membranes via physical cross-bridges. Specifically, we employed double-end-anchored poly(ethylene glycol)s (DEA-PEGs)—hydrophilic PEG tethers with hydrophobic tails on both ends. Using differential-interference-contrast optical microscopy, synchrotron small angle X-ray scattering (SAXS), and cryogenic electron microscopy, we investigated the ability of DEA-PEGs to mediate assembly in the dilute regime on multiple length scales and on practical time scales. The PEG length, anchor hydrophobicity, and molar fraction of DEA-PEG molecules within a membrane strongly affect the assembly properties. Additional tuning of the intermembrane interactions can be achieved by adding repulsive interactions via PEG-lipids (steric) or cationic lipids to the DEA-PEG-mediated attractions. Further, while the optical and electron microscope imaging methods provided qualitative evidence of the ability of DEA-PEGs to assemble liposomes, the SAXS measurements and quantitative line-shape analysis in dilute preparations demonstrated that the ensemble average of loosely organized liposomal assemblies maintains DEA-PEG concentration-dependent tethering on defined nanometer length scales. For cationic liposome–DNA nanoparticles (CL–DNA NPs), aggregation induced by DEA-PEGs decreased internalization of NPs by cells, but tuning the DEA-PEG-induced attractions by adding repulsive steric interactions via PEG-lipids limited aggregation and increased NP uptake. However, confocal microscopy imaging together with colocalization studies with Rab11 and LysoTracker as markers of intracellular pathways showed that modifying CL–DNA NPs with DEA-PEGs alters their interactions with the plasma and endosomal membranes.

- x-ray scattering↗
DOE OSTI2020

Experimental demonstration of broadband solar absorption beyond the lambertian limit in certain thin silicon photonic crystals

The tantalizing possibility of 31% solar-to-electric power conversion efficiency in thin film crystalline silicon solar cell architectures relies essentially on solar absorption well beyond the Lambertian light trapping limit (Bhattacharya and John in Nat Sci Rep 9:12482, 2019). Up to now, no solar cell architecture has exhibited above-Lambertian solar absorption, integrated over the broad solar spectrum. In this work, we experimentally demonstrate two types of photonic crystal (PhC) solar cells architectures that exceed Lambertian light absorption, integrated over the entire 300–1,200 nm wavelength band. These measurements confirm theoretically predicted wave-interference-based optical resonances associated with long lifetime, slow-light modes and parallel-to-interface refraction. These phenomena are beyond the realm of ray optics. Using two types of 10-μm thick PhC’s, first an Inverted Pyramid PhC with lattice constant a= 2,500 nm and second a Teepee PhC with a = 1,200 nm, we observe solar absorption well beyond the Lambertian limit over λ = 950–1,200 nm. Our absorption measurements correspond to the maximum-achievable-photocurrent-density (MAPD), under AM1.5G illumination at 4-degree incident angle, 41.29 and 41.52 mA/cm2 for the Inverted Pyramid and Teepee PhC, respectively, in agreement with wave-optics, numerical simulations. Both of these values exceed the MAPD (= 39.63 mA/cm2) corresponding to the Lambertian limit for a 10-μm thick silicon for solar absorption over the 300–1,200 nm band.

36 MATERIALS SCIENCE↗