411 research outputs found
External quantum efficiency enhancement by photon recycling with backscatter evasion
The nonunity quantum efficiency (QE) in photodiodes (PD) causes deterioration
of signal quality in quantum optical experiments due to photocurrent loss as
well as the introduction of vacuum fluctuations into the measurement. In this
paper, we report that the external QE enhancement of a PD was demonstrated by
recycling the reflected photons. The external QE for an InGaAs PD was increased
by 0.01 - 0.06 from 0.86 - 0.92 over a wide range of incident angles. Moreover,
we confirmed that this technique does not increase backscattered light when the
recycled beam is properly misaligned
Proximity AE doublets analysis for subsurface fracture measurement.
Proximity Acoustic Emission (AE) doublets analysis is used for subsurface fracture measurement. AE is a microseismic event. Location and shape of subsurface fracture is estimated from distribution of AE sources. Measurement of subsurface fracture is important in many areas of human activities associating with the Earth. Motion of subsurface fracture causes earthquakes. Geothermal energy is extracted from subsurface fracture reservoirs in which steam and hot water are stored. Carbon dioxide is also stored in tiny spaces of subsurface fracture. Proximity AE doublet analysis is a new method in which fine structures of subsurface fracture can be estimated. Proximity AE doublets have a similar waveform, and they occur in a succession with an interval that is less than 1 s. Accurate relative location between AE sources can be realized because a medium, in which AE waves propagate, does not change during the interval. Intervals of P-wave and S-wave between proximity AE doublets are detected in cepstrum analysis. Proximity AE doublets have one or two peaks at their intervals in their cepstrum. In my analysis I also show relative locations between AE sources of proximity AE doublets
Phase transition in compressed sensing with horseshoe prior
In Bayesian statistics, horseshoe prior has attracted increasing attention as
an approach to the sparse estimation. The estimation accuracy of compressed
sensing with the horseshoe prior is evaluated by statistical mechanical method.
It is found that there exists a phase transition in signal recoverability in
the plane of the number of observations and the number of nonzero signals and
that the recoverability phase is more extended than that using the well-known
norm regularization.Comment: 9pages, 5figure
Axion Dark Matter Search with Interferometric Gravitational Wave Detectors
Axion dark matter differentiates the phase velocities of the
circular-polarized photons. In this Letter, a scheme to measure the phase
difference by using a linear optical cavity is proposed. If the scheme is
applied to the Fabry-P\'erot arm of Advanced LIGO-like (Cosmic-Explorer-like)
gravitational wave detector, the potential sensitivity to the axion-photon
coupling constant, , reaches GeV GeV at the axion mass
eV ( eV) and remains at around
this sensitivity for 3 orders of magnitude in mass. Furthermore, its
sensitivity has a sharp peak reaching
GeV GeV at eV
( eV). This sensitivity can be achieved without loosing
any sensitivity to gravitational waves.Comment: 7 pages, 2 figure
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