1,178 research outputs found
High dispersive and monolithic 100% efficiency grisms
We present a type of grism, a series combination of transmission grating and
prism, in which we reduce the number of diffraction orders and achieve a
configuration with very high angular dispersion. The grism can be fabricated
from a single dielectric material and requires no metallic or dielectric film
layers for high transmission diffraction efficiency. One can reach 100% in the
-1st transmission diffraction order and the equal damage threshold as the
dielectric bulk material. We realized such an element in fused silica with an
efficiency of more then 99%. The bevel backside reflection is reduced by a
statistical antireflective structure, so we measured an efficiency of the
entire grism of 95% at a single wavelength
La evaluación y acreditación de la calidad en América Centra
En América Central, el Consejo Superior Universitario Centroamericano (CSUCA)1 ha sido el organismo pionero, no sólo de la integración regional de la educación superior, sino también de los procesos de aseguramiento de la calidad académica y del reconocimiento regional de estudios y tÃtulos profesionales.Peer Reviewe
Cancellation of lateral displacement noise of 3-port gratings for coupling light to cavities
Reflection gratings enable light coupling to optical cavities without
transmission through substrates. Gratings that have three ports and are mounted
in second-order Littrow configuration even allow the coupling to high-finesse
cavities using low diffraction efficiencies. In contrast to conventional
transmissive cavity couplers, however, the phase of the diffracted light
depends on the lateral position of the grating, which introduces an additional
noise coupling. Here we experimentally demonstrate that this kind of noise
cancels out once both diffracted output ports of the grating are combined. We
achieve the same signal-to-shot-noise ratio as for a conventional coupler. From
this perspective, 3-port grating couplers in second-order Littrow configuration
remain a valuable approach to reducing optical absorption of cavity coupler
substrates in future gravitational wave detectors
Asymmetric transmission of linearly polarized light at optical metamaterials
We experimentally demonstrate a three-dimensional chiral optical metamaterial
that exhibits an asymmetric transmission for forwardly and backwardly
propagating linearly polarized light. The observation of this novel effect
requires a metamaterial composed of three-dimensional chiral metaatoms without
any rotational symmetry. Our analysis is supported by a systematic
investigation of the transmission matrices for arbitrarily complex, lossy media
that allows deriving a simple criterion for asymmetric transmission in an
arbitrary polarization base. Contrary to physical intuition, in general the
polarization eigenstates in such three-dimensional and low-symmetry
metamaterials do not obey fxed relations and the associated transmission
matrices cannot be symmetrized
Table-Top Milliwatt-Class Extreme Ultraviolet High Harmonic Light Source
Extreme ultraviolet (XUV) lasers are essential for the investigation of
fundamental physics. Especially high repetition rate, high photon flux sources
are of major interest for reducing acquisition times and improving signal to
noise ratios in a plethora of applications. Here, an XUV source based on
cascaded frequency conversion is presented, which delivers due to the drastic
better single atom response for short wavelength drivers, an average output
power of (832 +- 204) {\mu}W at 21.7 eV. This is the highest average power
produced by any HHG source in this spectral range surpassing precious
demonstrations by more than a factor of four. Furthermore, a narrow-band
harmonic at 26.6 eV with a relative energy bandwidth of only {\Delta}E/E= 1.8 x
10E-3 has been generated, which is of high interest for high precision
spectroscopy experiments.Comment: 4 Pages, 4 Picture
High photon flux table-top coherent extreme ultraviolet source
High harmonic generation (HHG) enables extreme ultraviolet radiation with
table-top setups. Its exceptional properties, such as coherence and
(sub)-femtosecond pulse durations, have led to a diversity of applications.
Some of these require a high photon flux and megahertz repetition rates, e.g.
to avoid space charge effects in photoelectron spectroscopy. To date this has
only been achieved with enhancement cavities. Here, we establish a novel route
towards powerful HHG sources. By achieving phase-matched HHG of a megahertz
fibre laser we generate a broad plateau (25 eV - 40 eV) of strong harmonics,
each containing more than photons/s, which constitutes an increase by
more than one order of magnitude in that wavelength range. The strongest
harmonic (H25, 30 eV) has an average power of 143 W (
photons/s). This concept will greatly advance and facilitate applications in
photoelectron or coincidence spectroscopy, coherent diffractive imaging or
(multidimensional) surface science
Mechanical losses in low loss materials studied by Cryogenic Resonant Acoustic spectroscopy of bulk materials (CRA spectroscopy)
Mechanical losses of crystalline silicon and calcium fluoride have been
analyzed in the temperature range from 5 to 300 K by our novel mechanical
spectroscopy method, cryogenic resonant acoustic spectroscopy of bulk materials
(CRA spectrocopy). The focus lies on the interpretation of the measured data
according to phonon-phonon interactions and defect induced losses in
consideration of the excited mode shape.Comment: 4 pages, 4 figures, proceedings of the PHONONS 2007, submitted to
Journal of Physics: Conference Serie
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