3,975 research outputs found
Real-time phasefront detector for heterodyne interferometers
We present a real-time differential phasefront detector sensitive to better
than 3 mrad rms, which corresponds to a precision of about 500 pm. This
detector performs a spatially resolving measurement of the phasefront of a
heterodyne interferometer, with heterodyne frequencies up to approximately 10
kHz. This instrument was developed as part of the research for the LISA
Technology Package (LTP) interferometer, and will assist in the manufacture of
its flight model. Due to the advantages this instrument offers, it also has
general applications in optical metrology
FIRI - a Far-Infrared Interferometer
Half of the energy ever emitted by stars and accreting objects comes to us in
the FIR waveband and has yet to be properly explored. We propose a powerful
Far-InfraRed Interferometer mission, FIRI, to carry out high-resolution imaging
spectroscopy in the FIR. This key observational capability is essential to
reveal how gas and dust evolve into stars and planets, how the first luminous
objects in the Universe ignited, how galaxies formed, and when super-massive
black holes grew. FIRI will disentangle the cosmic histories of star formation
and accretion onto black holes and will trace the assembly and evolution of
quiescent galaxies like our Milky Way. Perhaps most importantly, FIRI will
observe all stages of planetary system formation and recognise Earth-like
planets that may harbour life, via its ability to image the dust structures in
planetary systems. It will thus address directly questions fundamental to our
understanding of how the Universe has developed and evolved - the very
questions posed by ESA's Cosmic Vision.Comment: Proposal developed by a large team of astronomers from Europe, USA
and Canada and submitted to the European Space Agency as part of "Cosmic
Vision 2015-2025
Polarization Imperfections of Light in Interferometry
DisertaÄŤnĂ práce pojednává o polarizaÄŤnĂch nedokonalostech optickĂ˝ch komponentĹŻ, kterĂ© jsou vyuĹľĂvány ke kontrole a k transformaci polarizaÄŤnĂho stavu svÄ›tla. ZĂskanĂ© teoretickĂ© vĂ˝sledky jsou pak vyuĹľity ve vybranĂ˝ch aplikacĂch, jeĹľ ke svĂ© ÄŤinnosti vyuĹľĂvajĂ právÄ› polarizace svÄ›tla. KonkrĂ©tnÄ› se jedná o zaĹ™ĂzenĂ měřĂcĂ vibrace oscilujĂcĂch objektĹŻ, dále o interferenÄŤnĂ měřenĂ dvojlomu v transparentnĂch materiálech a koneÄŤnÄ›, o vybraná tĂ©mata z optickĂ© kvantovĂ© komunikace.The emphasis of the dissertation is put on the investigating of polarization imperfections of optical components which are used to control and transform polarization of light. The theoretical results of this investigation are then applied to different applications which exploit light polarization, namely to the arrangements for high-resolution measurement of vibrating targets, to interferometric measurements for the determination of stress-induced birefringence in transparent materials and to the selected topics in quantum optical communication.
THz Instruments for Space
Terahertz technology has been driven largely by applications in astronomy and space science. For more than three decades cosmochemists, molecular spectroscopists, astrophysicists, and Earth and planetary scientists have used submillimeter-wave or terahertz sensors to identify, catalog and map lightweight gases, atoms and molecules in Earth and planetary atmospheres, in regions of interstellar dust and star formation, and in new and old galaxies, back to the earliest days of the universe, from both ground based and more recently, orbital platforms. The past ten years have witnessed the launch and successful deployment of three satellite instruments with spectral line heterodyne receivers above 300 GHz (SWAS, Odin, and MIRO) and a fourth platform, Aura MLS, that reaches to 2520 GHz, crossing the terahertz threshold from the microwave side for the first time. The former Soviet Union launched the first bolometric detectors for the submillimeter way back in 1974 and operated the first space based submillimeter wave telescope on the Salyut 6 station for four months in 1978. In addition, continuum, Fourier transform and spectrophotometer instruments on IRAS, ISO, COBE, the recent Spitzer Space Telescope and Japan's Akari satellite have all encroached into the submillimeter from the infrared using direct detection bolometers or photoconductors. At least two more major satellites carrying submillimeter wave instruments are nearing completion, Herschel and Planck, and many more are on the drawing boards in international and national space organizations such as NASA, ESA, DLR, CNES, and JAXA. This paper reviews some of the programs that have been proposed, completed and are still envisioned for space applications in the submillimeter and terahertz spectral range
Longer-Baseline Telescopes Using Quantum Repeaters
We present an approach to building interferometric telescopes using ideas of
quantum information. Current optical interferometers have limited baseline
lengths, and thus limited resolution, because of noise and loss of signal due
to the transmission of photons between the telescopes. The technology of
quantum repeaters has the potential to eliminate this limit, allowing in
principle interferometers with arbitrarily long baselines.Comment: 10 pages, v2 improved clarit
Technology needs assessment of an atmospheric observation system for tropospheric research missions, part 1
The technology advancements needed to implement the atmospheric observation satellite systems for air quality research were identified. Tropospheric measurements are considered. The measurements and sensors are based on a model of knowledge objectives in atmospheric science. A set of potential missions and attendant spacecraft and sensors is postulated. The results show that the predominant technology needs will be in passive and active sensors for accurate and frequent global measurements of trace gas concentration profiles
Measurement of the absolute wavefront curvature radius in a heterodyne interferometer
We present an analytical derivation of the coupling parameter relating the
angle between two interfering beams in a heterodyne interferometer to the
differential phase-signals detected by a quadrant photo-diode. This technique,
also referred to as Differential Wavefront Sensing (DWS), is commonly used in
space-based gravitational wave detectors to determine the attitude of a
test-mass in one of the interferometer arms from the quadrant diode signals.
Successive approximations to the analytical expression are made to simplify the
investigation of parameter dependencies. Motivated by our findings, we propose
a new measurement method to accurately determine the absolute wave-front
curvature of a single measurement beam. We also investigate the change in
coupling parameter when the interferometer "test-mirror" is moved from its
nominal position, an effect which mediates the coupling of mirror displacement
noise into differential phase-measurements.Comment: double-spaced, 21 pages, 5 figure
Experimental Design for the LATOR Mission
This paper discusses experimental design for the Laser Astrometric Test Of
Relativity (LATOR) mission. LATOR is designed to reach unprecedented accuracy
of 1 part in 10^8 in measuring the curvature of the solar gravitational field
as given by the value of the key Eddington post-Newtonian parameter \gamma.
This mission will demonstrate the accuracy needed to measure effects of the
next post-Newtonian order (~G^2) of light deflection resulting from gravity's
intrinsic non-linearity. LATOR will provide the first precise measurement of
the solar quadrupole moment parameter, J2, and will improve determination of a
variety of relativistic effects including Lense-Thirring precession. The
mission will benefit from the recent progress in the optical communication
technologies -- the immediate and natural step above the standard radio-metric
techniques. The key element of LATOR is a geometric redundancy provided by the
laser ranging and long-baseline optical interferometry. We discuss the mission
and optical designs, as well as the expected performance of this proposed
mission. LATOR will lead to very robust advances in the tests of Fundamental
physics: this mission could discover a violation or extension of general
relativity, or reveal the presence of an additional long range interaction in
the physical law. There are no analogs to the LATOR experiment; it is unique
and is a natural culmination of solar system gravity experiments.Comment: 16 pages, 17 figures, invited talk given at ``The 2004 NASA/JPL
Workshop on Physics for Planetary Exploration.'' April 20-22, 2004, Solvang,
C
State-of-the art of acousto-optic sensing and imaging of turbid media
Acousto-optic (AO) is an emerging hybrid technique for measuring optical contrast in turbid media using coherent light and ultrasound (US). A turbid object is illuminated with a coherent light source leading to speckle formation in the remitted light. With the use of US, a small volume is selected,which is commonly referred to as the “tagging” volume. This volume acts as a source of modulated light, where modulation might involve phase and intensity change. The tagging volume is created by focusing ultrasound for good lateral resolution; the axial resolution is accomplished by making either the US frequency, amplitude, or phase time-dependent. Typical resolutions are in the order of 1 mm. We will concentrate on the progress in the field since 2003. Different schemes will be discussed to detect the modulated photons based on speckle detection, heterodyne detection, photorefractive crystal (PRC) assisted detection, and spectral hole burning (SHB) as well as Fabry-Perot interferometers. The SHB and Fabry-Perot interferometer techniques are insensitive to speckle decorrelation and therefore suitable for in vivo imaging. However, heterodyne and PRC methods also have potential for in vivo measurements. Besides measuring optical properties such as scattering and absorption, AO can be applied in fluorescence and elastography applications
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