27,547 research outputs found
A low-loss photonic silica nanofiber for higher-order modes
Optical nanofibers confine light to subwavelength scales, and are of interest
for the design, integration, and interconnection of nanophotonic devices. Here
we demonstrate high transmission (> 97%) of the first family of excited modes
through a 350 nm radius fiber, by appropriate choice of the fiber and precise
control of the taper geometry. We can design the nanofibers so that these modes
propagate with most of their energy outside the waist region. We also present
an optical setup for selectively launching these modes with less than 1%
fundamental mode contamination. Our experimental results are in good agreement
with simulations of the propagation. Multimode optical nanofibers expand the
photonic toolbox, and may aid in the realization of a fully integrated
nanoscale device for communication science, laser science or other sensing
applications.Comment: 12 pages, 5 figures, movies available onlin
An analytical and experimental investigation of resistojet plumes
As a part of the electrothermal propulsion plume research program at the NASA Lewis Research Center, efforts have been initiated to analytically and experimentally investigate the plumes of resistojet thrusters. The method of G.A. Simons for the prediction of rocket exhaust plumes is developed for the resistojet. Modifications are made to the source flow equations to account for the increased effects of the relatively large nozzle boundary layer. Additionally, preliminary mass flux measurements of a laboratory resistojet using CO2 propellant at 298 K have been obtained with a cryogenically cooled quartz crystal microbalance (QCM). There is qualitative agreement between analysis and experiment, at least in terms of the overall number density shape functions in the forward flux region
Intermodal Energy Transfer in a Tapered Optical Fiber: Optimizing Transmission
We present an experimental and theoretical study of the energy transfer
between modes during the tapering process of an optical nanofiber through
spectrogram analysis. The results allow optimization of the tapering process,
and we measure transmission in excess of 99.95% for the fundamental mode. We
quantify the adiabaticity condition through calculations and place an upper
bound on the amount of energy transferred to other modes at each step of the
tapering, giving practical limits to the tapering angle.Comment: 29 pages, 17 figure
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What does the future hold for utility electricity efficiency programs?
This study develops projections of future spending and savings from electricity efficiency programs funded by electric utility customers in the United States through 2030 based on three scenarios. Our analysis relies on detailed bottom-up modeling of current state energy efficiency policies, demand-side management and integrated resource plans, and regulatory decisions. The three scenarios represent a range of potential outcomes given the policy environment at the time of the study and uncertainties in the broader economic and state policy environment in each state. We project spending to increase to 11.1 billion in 2030 and remains relatively flat in the low case ($6.8 billion in 2030). Our analysis suggests that electricity efficiency programs funded by utility customers will continue to impact load growth significantly at least through 2030, as savings as a percent of retail sales are forecast at 0.7 percent in the medium scenario and 0.98 percent in the high scenario
Application of advanced on-board processing concepts to future satellite communications systems
An initial definition of on-board processing requirements for an advanced satellite communications system to service domestic markets in the 1990's is presented. An exemplar system architecture with both RF on-board switching and demodulation/remodulation baseband processing was used to identify important issues related to system implementation, cost, and technology development
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Data assimilation insights on selecting the most valuable atmospheric measurements
We discuss how objective guidance on selecting the most valuable atmospheric measurements on future Mars spacecraft missions can be provided through already developed Martian atmospheric data assimilation systems, and in particular through Observing System Simulation Experiments (OSSEs) which are widely used to design instruments for the Earth’s atmosphere
Dispersive Photon Blockade in a Superconducting Circuit
Mediated photon-photon interactions are realized in a superconducting
coplanar waveguide cavity coupled to a superconducting charge qubit. These
non-resonant interactions blockade the transmission of photons through the
cavity. This so-called dispersive photon blockade is characterized by measuring
the total transmitted power while varying the energy spectrum of the photons
incident on the cavity. A staircase with four distinct steps is observed and
can be understood in an analogy with electron transport and the Coulomb
blockade in quantum dots. This work differs from previous efforts in that the
cavity-qubit excitations retain a photonic nature rather than a hybridization
of qubit and photon and provides the needed tolerance to disorder for future
condensed matter experiments.Comment: 4 pages, 3 figure
Ultrahigh Transmission Optical Nanofibers
We present a procedure for reproducibly fabricating ultrahigh transmission
optical nanofibers (530 nm diameter and 84 mm stretch) with single-mode
transmissions of 99.95 0.02%, which represents a loss from tapering of
2.6 10 dB/mm when normalized to the entire stretch. When
controllably launching the next family of higher-order modes on a fiber with
195 mm stretch, we achieve a transmission of 97.8 2.8%, which has a loss
from tapering of 5.0 10 dB/mm when normalized to the
entire stretch. Our pulling and transfer procedures allow us to fabricate
optical nanofibers that transmit more than 400 mW in high vacuum conditions.
These results, published as parameters in our previous work, present an
improvement of two orders of magnitude less loss for the fundamental mode and
an increase in transmission of more than 300% for higher-order modes, when
following the protocols detailed in this paper. We extract from the
transmission during the pull, the only reported spectrogram of a fundamental
mode launch that does not include excitation to asymmetric modes; in stark
contrast to a pull in which our cleaning protocol is not followed. These
results depend critically on the pre-pull cleanliness and when properly
following our pulling protocols are in excellent agreement with simulations.Comment: 32 pages, 10 figures, accepted to AIP Advance
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