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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.

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At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

Strain sensor comprising a strain sensitive, two-mode optical

A strain sensor uses an optical fiber including a strain sensitive portion and at least one strain insensitive portion. The strain sensitive portion is mounted on the surface of a structure at a location where a strain is desired to be measured. The strain insensitive portion(s) may be fused to the strain sensitive portion to transmit light therethrough, so that the resulting pattern may be detected to determine the amount of strain by comparison with a similar fiber not subjected to strain, or with the light pattern produced when the fiber is not under strain.

Egalon, Claudio Oliveira↗
DOE OSTI2016

Localized modes in optics of photonic liquid crystals with local anisotropy of absorption

The localized optical modes in spiral photonic liquid crystals are theoretically studied for the certainty at the example of chiral liquid crystals (CLCs) for the case of CLC with an anisotropic local absorption. The model adopted here (absence of dielectric interfaces in the structures under investigation) makes it possible to get rid of mixing of polarizations on the surfaces of the CLC layer and of the defect structure and to reduce the corresponding equations to only the equations for light with polarization diffracting in the CLC. The dispersion equations determining connection of the edge mode (EM) and defect mode (DM) frequencies with the CLC layer parameters (anisotropy of local absorption, CLC order parameter) and other parameters of the DMS are obtained. Analytic expressions for the transmission and reflection coefficients of CLC layer and DMS for the case of CLC with an anisotropic local absorption are presented and analyzed. It is shown that the CLC layers with locally anisotropic absorption reduce the EM and DM lifetimes (and increase the lasing threshold) in the way different from the case of CLC with an isotropic local absorption. Due to the Borrmann effect revealing of which is different at the opposite stop-band edges in the case of CLC layers with an anisotropic local absorption the EM life-times for the EM frequencies at the opposite stop-bands edges may be significantly different. The options of experimental observations of the theoretically revealed phenomena are briefly discussed.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Efficient photon coupling from a diamond nitrogen vacancy center by integration with silica fiber

A central goal in quantum information science is to efficiently interface photons with single optical modes for quantum networking and distributed quantum computing. Here, we introduce and experimentally demonstrate a compact and efficient method for the low-loss coupling of a solid-state qubit, the nitrogen vacancy (NV) center in diamond, with a single-mode optical fiber. In this approach, single-mode tapered diamond waveguides containing exactly one high quality NV memory are selected and integrated on tapered silica fibers. Numerical optimization of an adiabatic coupler indicates that near-unity-efficiency photon transfer is possible between the two modes. Experimentally, we find an overall collection efficiency between 16% and 37% and estimate a single photon count rate at saturation above 700 kHz. This integrated system enables robust, alignment-free, and efficient interfacing of single-mode optical fibers with single photon emitters and quantum memories in solids.

Optics↗
DOE OSTI2018

Effect of Material Structure on Photoluminescence of ZnO/MgO Core-Shell Nanowires

Zinc oxide (ZnO) nanowires are widely studied for use in ultraviolet optoelectronic devices, such as nanolasers and sensors. Nanowires (NWs) with an MgO shell exhibit enhanced band-edge photoluminescence (PL), a result previously attributed to passivation of ZnO defects. However, we find that processing the ZnO NWs under low oxygen partial pressure leads to an MgO-thickness-dependent PL enhancement owing to the formation of optical cavity modes. Conversely, processing under higher oxygen partial pressure leads to NWs that support neither mode formation nor band-edge PL enhancement. High-resolution electron microscopy and density-functional calculations implicate the ZnO m-plane surface morphology as the key determinant of core-shell structure and cavity-mode optics. A ZnO surface with atomic steps along the m-plane in the c-axis direction stimulates the growth of a smooth MgO shell that supports guided-wave optical modes and enhanced UV PL. On the other hand, a smoother ZnO surface leads to nucleation of a rough cladding layer which supports neither enhanced UV PL nor optical cavity modes. Finite-element analysis shows a clear correlation between allowed Fabry-Perot and whispering gallery modes and enhanced UV-PL. Finally, these results point the way to fabricating ZnO/MgO core-shell nanowires for more efficient UV nanolasers, scintillators, and sensors.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2020

Polarization diversity optical interface assembly

Examples herein relate to polarization diversity optical interface assemblies including a single mode optical fiber and first and second grating couplers disposed on a substrate. The first and second grating couplers are coupled to first and second waveguides, respectively. The assemblies further includes an optical connector to couple light between the single mode optical fiber and each of the first and second grating couplers. The optical connector includes a ferrule and a walk-off crystal. The ferrule is coupled to a portion of the single mode optical fiber. The walk-off crystal is configured to spatially separate the light into first and second orthogonal polarization modes prior to passing through the respective first and second grating couplers and/or combine the first and second polarization modes of the light prior to passing through the single mode optical fiber.

42 ENGINEERING↗
DOE OSTI2019

Measurement Error of Interferometers with Diffraction Reference Wave

An experimental setup and results on aberration of sources of a reference spherical wave (SRSW) based on a single-mode optical fiber with a subwavelength output aperture obtained with the aid of an optical part of recording system (OPRS) are presented. SRSW and OPRS are developed for referenceless interferometer with diffraction reference wave. Methods for minimization of the measurement error are proposed. The SRSW and OPRS provide subnanometer measurement accuracy for optics. An increase in the measurement accuracy of the interferometer to a picometer level is discussed.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2017

Plasmon-assisted optical vias for photonic ASICS

The present invention relates to optical vias to optically connect multilevel optical circuits. In one example, the optical via includes a surface plasmon polariton waveguide, and a first optical waveguide formed on a first substrate is coupled to a second optical waveguide formed on a second substrate by the surface plasmon polariton waveguide. In some embodiments, the first optical waveguide includes a transition region configured to convert light from an optical mode to a surface plasmon polariton mode or from a surface plasmon polariton mode to an optical mode.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Optical matter machines: angular momentum conversion by collective modes in optically bound nanoparticle arrays

The creation of optically powered self-assembling nano-to-meso-scale machines that do work is a long-standing goal in photonics. We demonstrate an optical matter (OM) machine that converts the spin angular momentum (SAM) of light into orbital angular momentum (OAM) to do mechanical work. The specific OM machine we study is based on a sixfold symmetric hexagonally ordered nanoparticle array that operates as an OM “gear” that is assembled and made to rotate in a circularly polarized Gaussian beam. The rotational symmetry of the OM gear leads to a selection rule for the allowed scattering modes based on their angular momentum. Electrodynamics calculations show that the collective scattering modes with the largest angular momentum scatter strongly in the transverse direction. Simulations and experiments show that the angular momentum that accompanies the scattered light causes a “negative torque” response on the OM gear and drives a “probe” particle placed outside the OM gear around the gear in an asymmetric force field analogously to Brownian ratchets. The gear–probe OM machine concept can be expanded to applications in nanofluidics and particle sorting.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2024

Nonreciprocal Dissipation Engineering via Strong Coupling with a Continuum of Modes

Optical nonreciprocity plays a key role in almost every optical system, directing light flow and protecting optical components from backscattered light. Controllable forms of on-chip nonreciprocity are needed for the robust operation of increasingly sophisticated photonic integrated circuits (PICs) in the context of classical and quantum computation, networking, communications, and sensing. However, it has been challenging to achieve wideband, low-loss optical nonreciprocity on-chip. In this paper, we demonstrate strong coupling and Rabi-like energy exchange between photonic bands, possessing a continuum of modes, to unlock nonreciprocity and frequency translation over wide optical bandwidths in silicon. Using a traveling-wave phonon field to drive indirect interband photonic transitions, we demonstrate band hybridization that enables an intriguing form of nonreciprocal dissipation engineering. Using the converted mode to create a nonreciprocal dissipation channel, we demonstrate a frequency-neutral, low-loss (less than 1 dB) isolator with high nonreciprocal contrast (more than 14 dB) and broad operating bandwidth (more than 59 GHz). Additionally, through the implementation of complete interband conversion, we demonstrate a high extinction (more than 55 dB) optical frequency translation operation with near-unity efficiency.

Zhou, Yishu↗
NASA NTRS1982

Polarization preserving single mode fiber optic coupler

A technique is described for fabrication of etched single mode fiber optical waveguide couplers which preserve the polarization state to within 0.0001. The coupling ratio is tunable over a broad range (0-9 percent) during fabrication. Back-coupling is less than 0.001, insertion loss is less than 1.5 dB, and coupling ratio thermal coefficient is about 1 percent per degree C.

Nelson, M. D.↗
DOE OSTI2015

Transition, coexistence, and interaction of vector localized waves arising from higher-order effects

We study vector localized waves on continuous wave background with higher-order effects in a two-mode optical fiber. The striking properties of transition, coexistence, and interaction of these localized waves arising from higher-order effects are revealed in combination with corresponding modulation instability (MI) characteristics. It shows that these vector localized wave properties have no analogues in the case without higher-order effects. Specifically, compared to the scalar case, an intriguing transition between bright–dark rogue waves and w-shaped–anti-w-shaped solitons, which occurs as a result of the attenuation of MI growth rate to vanishing in the zero-frequency perturbation region, is exhibited with the relative background frequency. In particular, our results show that the w-shaped–anti-w-shaped solitons can coexist with breathers, coinciding with the MI analysis where the coexistence condition is a mixture of a modulation stability and MI region. It is interesting that their interaction is inelastic and describes a fusion process. In addition, we demonstrate an annihilation phenomenon for the interaction of two w-shaped solitons which is identified essentially as an inelastic collision in this system. -- Highlights: •Vector rogue wave properties induced by higher-order effects are studied. •A transition between vector rogue waves and solitons is obtained. •The link between the transition and modulation instability (MI) is demonstrated. •The coexistence of vector solitons and breathers coincides with the MI features. •An annihilation phenomenon for the vector two w-shaped solitons is presented.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2017

Emergent Optical Phononic Modes upon Nanoscale Mesogenic Phase Transitions

The investigation of phononic collective excitations in soft matter systems at the molecular scale has always been challenging due to limitations of experimental techniques in resolving low-energy modes. Recent advances in inelastic X-ray scattering (IXS) enabled the study of such systems with unprecedented spectral contrast at meV excitation energies. In particular, it has become possible to shed light on the low-energy collective motions in materials whose morphology and phase behavior can easily be manipulated, such as mesogenic systems. The understanding of collective mode behavior with a Q-dependence is the key to implement heat management based on the control of a sample structure. The latter has great potential for a large number of energy-inspired innovations. As a first step toward this goal, we carried out high contrast IXS measurements on a liquid crystal sample, D7AOB, which exhibits solid-like dynamic features, such as the coexistence of longitudinal and transverse phononic modes. For the first time, we found that these terahertz phononic excitations persist in the crystal, smectic A, and isotropic phases. Furthermore, the intermediate smectic A phase is shown to support a van der Waals-mediated nonhydrodynamic mode with an optical-like phononic behavior. In conclusion, the tunability of the collective excitations at nanometer–terahertz scales via selection of the sample mesogenic phase represents a new opportunity to manipulate optomechanical properties of soft metamaterials.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Quasi-single-mode hybrid fibre with anomalous dispersion in the 1 μm range

We have proposed and demonstrated an approach for ensuring quasi-single-mode operation of a cylindrically symmetric hybrid fibre having anomalous dispersion at wavelengths around 1 μm. Basic to this approach are distinctions between spatial fibre mode distributions and the use of a high-loss ring layer in the region of a minimum in the electric field of the operating hybrid mode. (optical fibres)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

Modelling of rotation-induced frequency shifts in whispering gallery modes

We study the angular velocity sensors based on whispering gallery mode resonators. Rotation of such resonators gives rise to various effects that can cause a spectral shift of their modes. Optical methods allow this shift to be determined with high precision, which can be used practically to measure the angular velocity in inertial orientation and navigation systems. The basic principles of constructing the angular velocity sensors utilising these effects are considered, their advantages and drawbacks are indicated. We also study the interrelation between the effects and the possibility of their mutual influence on each other. Based on the analytical studies of the effects, we consider the possibility of their combined application for angular velocity measurements. (review)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2024

Large-mode-area optical fibers and optical fiber amplifiers in the eye-safe regime

The present technology provides large mode area optical fibers engineered to have normal dispersion around 1600 nm, enabling high power Raman amplification at eye safer wavelengths. The fibers can have a main core and one or more side cores disposed relative to the main core so that modes of the main core and the one or more side cores hybridize into supermodes with modified dispersion.

Pax, Paul H.↗