4,939 research outputs found
Demonstration of 3-port grating phase relations
We experimentally demonstrate the phase relations of 3-port gratings by
investigating 3-port coupled Fabry-Perot cavities. Two different gratings which
have the same 1st order diffraction efficiency but differ substantially in
their 2nd order diffraction efficiency have been designed and manufactured.
Using the gratings as couplers to Fabry-Perot cavities we could validate the
results of an earlier theoretical description of the phases at a three port
grating
Experimental demonstration of continuous variable purification of squeezed states
We report on the first experimental demonstration of purification of
nonclassical continuous variable states. The protocol uses two copies of
phase-diffused states overlapped on a beam splitter and provides Gaussified,
less mixed states with the degree of squeezing improved. The protocol uses only
linear optical devices such as beam splitters and homodyne detection, thereby
proving these optical elements can be used for successful purification of this
type of state decoherence which occurs in optical transmission channels
Small Business Capital Structure Choice
A simple single-period model of entrepreneurial capital structure choice under conditions of informational asymmetry is developed. The uncertain terminal cash flow generated by a business venture is assumed to depend on both the amount of effort provided by the entrepreneur and the quality of the business venture. External financing induces the effort-averse entrepreneur to reduce the amount of effort he exerts. However, by astute choice of capital structure, the entrepreneur can mitigate this effect. It is shown that this entails financing high quality ventures with debt and low quality ventures with equity. This explains the predominance of debt in the capital structures of small firms
Input-output relations for a 3-port grating coupled Fabry-Perot cavity
We analyze an optical 3-port reflection grating by means of a scattering
matrix formalism. Amplitude and phase relations between the 3 ports, i.e. the 3
orders of diffraction are derived. Such a grating can be used as an
all-reflective, low-loss coupler to Fabry-Perot cavities. We derive the input
output relations of a 3-port grating coupled cavity and find distinct
properties not present in 2-port coupled cavities. The cavity relations further
reveal that the 3-port coupler can be designed such that the additional cavity
port interferes destructively. In this case the all-reflective, low-loss,
single-ended Fabry-Perot cavity becomes equivalent to a standard transmissive,
2-port coupled cavity
Forecast, observation and modelling of a deep stratospheric intrusion event over Europe
A wide range of measurements was carried out in central and southeastern Europe within the framework of the EU-project STACCATO (Influence of Stratosphere-Troposphere Exchange in a Changing Climate on Atmospheric Transport and Oxidation Capacity) with the principle goal to create a comprehensive data set on stratospheric air intrusions into the troposphere along a rather frequently observed pathway over central Europe from the North Sea to the Mediterranean Sea. The measurements were based on predictions by suitable quasi-operational trajectory calculations using ECMWF forecast data. A predicted deep Stratosphere to Troposphere Transport (STT) event, encountered during the STACCATO period on 20-21 June 2001, could be followed by the measurements network almost from its inception. Observations provide evidence that the intrusion affected large parts of central and southeastern Europe. Especially, the ozone lidar observations on 20-21 June 2001 at Garmisch-Partenkirchen, Germany captured the evolution of two marked tongues of high ozone with the first one reaching almost a height of 2 km, thus providing an excellent data set for model intercomparisons and validation. In addition, for the first time to our knowledge concurrent measurements of the cosmogenic radionuclides <sup>10</sup>Be and <sup>7</sup>Be and their ratio <sup>10</sup>Be/<sup>7</sup>Be are presented together as stratospheric tracers in a case study of a stratospheric intrusion. The ozone tracer columns calculated with the FLEXPART model were found to be in good agreement with water vapour satellite images, capturing the evolution of the observed dry streamers of stratospheric origin. Furthermore, the time-height cross section of ozone tracer simulated with FLEXPART over Garmisch-Partenkirchen captures with many details the evolution of the two observed high-ozone filaments measured with the IFU lidar, thus demonstrating the considerable progress in model simulations. Finally, the modelled ozone (operationally available since October 1999) from the ECMWF (European Centre for Medium-Range Weather Forecasts) atmospheric model is shown to be in very good agreement with the observations during this case study, which provides the first successful validation of a chemical tracer that is used operationally in a weather forecast model. This suggests that coupling chemistry and weather forecast models may significantly improve both weather and chemical forecasts in the future
Cryogenic Q-factor measurement of optical substrates for optimization of gravitational wave detectors
Future generations of gravitational wave interferometers are likely to be operated at cryogenic temperatures because one of the sensitivity limiting factors of the present generation is the thermal noise of end mirrors and beam splitters that occurs in the optical substrates as well as in the dielectric coatings. A possible method for minimizing thermal noise is cooling to cryogenic temperatures, maximizing the mechanical quality factor Q, and maximizing the eigenfrequencies of the substrate. We present experimental details of a new cryogenic apparatus that is suitable for the measurement of the temperature-dependent Q-factor of reflective, transmissive as well as nano-structured grating optics down to 5 K. In particular, the SQUID-based and the optical interferometric approaches to the measurement of the amplitude of vibrating test bodies are compared and the method of ring-down recording is described
Three-port beam splitters-combiners for interferometer applications
We derive generic phase and amplitude coupling relations for beam
splitters-combiners that couple a single port with three output ports or input
ports, respectively. We apply the coupling relations to a reflection grating
that serves as a coupler to a single-ended Fabry-Perot ring cavity. In the
impedance-matched case such an interferometer can act as an all-reflective ring
mode cleaner. It is further shown that in the highly undercoupled case almost
complete separation of carrier power and phase signal from a cavity strain can
be achieved
Preparing the bound instance of quantum entanglement
Among the possibly most intriguing aspects of quantum entanglement is that it
comes in "free" and "bound" instances. Bound entangled states require entangled
states in preparation but, once realized, no free entanglement and therefore no
pure maximally entangled pairs can be regained. Their existence hence certifies
an intrinsic irreversibility of entanglement in nature and suggests a
connection with thermodynamics. In this work, we present a first experimental
unconditional preparation and detection of a bound entangled state of light. We
consider continuous-variable entanglement, use convex optimization to identify
regimes rendering its bound character well certifiable, and realize an
experiment that continuously produced a distributed bound entangled state with
an extraordinary and unprecedented significance of more than ten standard
deviations away from both separability and distillability. Our results show
that the approach chosen allows for the efficient and precise preparation of
multimode entangled states of light with various applications in quantum
information, quantum state engineering and high precision metrology.Comment: The final version accounts for a recent comment in Nature Physics
[24] clarifying that a previous claim of having generated bound entanglement
[23] was not supported by the authors' data. We also extended our
introduction and discussion and also added reference
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