ESO seminar December 2005 Dainis Dravins Lund Observatory.
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Transcript of ESO seminar December 2005 Dainis Dravins Lund Observatory.
What information is contained in light?
What is being observed ? What is not ?
Quantum optics in astronomy?Quantum optics in astronomy?
BLACKBODY ---
SCATTERED ---
SYNCHROTRON ---
LASER ---
CHERENKOV ---
COHERENT ---
WAVELE
NG
TH
& P
OLA
RIZ
ATIO
N F
ILTERS
OBSERVER
BLACKBODY ---
SCATTERED ---
SYNCHROTRON ---
LASER ---
CHERENKOV ---
COHERENT ---
WAVELE
NG
TH
& P
OLA
RIZ
ATIO
N F
ILTERS
OBSERVER
Intensity interferometryIntensity interferometry
Narrabri stellar intensity interferomer circa 1970 (R.Hanbury Brown, R.Q.Twiss et al., University of Sydney)
Intensity interferometryIntensity interferometry
R.Hanbury Brown, J.Davis, L.R.Allen, MNRAS 137, 375 (1967)
Information content of light. IInformation content of light. I
D.Dravins, ESO Messenger 78, 9 (1994)
Galileo’s telescopes (1609)
Instruments measuring first-order spatial coherence
Hubble Space Telescope (1990)
Information content of light. IIInformation content of light. II
D.Dravins, ESO Messenger 78, 9 (1994)
Semi-classical model of light: (a) Constant classical intensity produces photo-electrons with Poisson statistics; (b) Thermal light results in a compound
Poisson process with a Bose-Einstein distribution, and ‘bunching’ of the photo-electrons (J.C. Dainty)
Information content of light. IIIInformation content of light. III
D.Dravins, ESO Messenger 78, 9 (1994)
Early thoughts about lasers in space
Early thoughts about lasers in space
D. Menzel : Physical Processes in Gaseous Nebulae. I , ApJ 85, 330 (1937)
Hydrogen recombination lasers & masers in MWC 349A
Circumstellar disk surrounding the hot star.Maser emissions occur in outer regions while lasers operate nearer to the central
star.
Quantum effects in cosmic light
Quantum effects in cosmic light
Hydrogen recombinationlasers & masersin MWC 349 A
K.H. Hofmann; Y. Balega; N.R. Ikhsanov; A.S. Miroshnichenko; G. WeigeltBispectrum speckle interferometry of the B[e] star MWC 349AA&A 395, 891 (2002)
Two-dimensional visibilityof MWC 349, from speckle
interferometry on theSAO 6m telescope (J-band; λ 1.24 μm,resolution 43 mas).
It appears that the star
is surrounded by acircumstellar disk
seen almost edge-on.
V. Strelnitski; M.R. Haas; H.A. Smith; E.F. Erickson; S.W. Colgan; D.J. HollenbachFar-Infrared Hydrogen Lasers in the Peculiar Star MWC 349A Science 272, 1459 (1996)
V. Strelnitski; M.R. Haas; H.A. Smith; E.F. Erickson; S.W. Colgan; D.J. HollenbachFar-Infrared Hydrogen Lasers in the Peculiar Star MWC 349A Science 272, 1459 (1996)
M. Spaans & C.A. NormanHydrogen Recombination Line Masers at the Epochs of Recombination and ReionizationApJ 488, 27 (1997)
FIRSTMASERSIN THE
UNIVERSE
The black inner regiondenotes the evolutionof the universe before
decoupling.
Arrows indicate maseremission from the epoch
of recombination andreionization.
M. Spaans & C.A. NormanHydrogen Recombination Line Masers at the Epochs of Recombination and ReionizationApJ 488, 27 (1997)
Top to bottom:Three maser spots withnα = 60 produced at z 1000, if regions with density fluctuationsexisted at recombination.
Superposed structure resultsfrom absorption during reionization.Left to right:Profiles for other frequenciesalong the same line of sight.
Brightness temperatures 10 MK are expected.
Synergy OWL ― SKASynergy OWL ― SKA
SKA: Hydrogen recombination
lasers in the very early Universe
OWL: Hydrogen recombination lasers in
the nearby Universe
Model of a compact gas condensation near η Car with its Strömgren boundarybetween photoionized (H II) and neutral (H I) regions
S. Johansson & V. S. LetokhovLaser Action in a Gas Condensation in the Vicinity of a Hot StarJETP Lett. 75, 495 (2002) = Pis’ma Zh.Eksp.Teor.Fiz. 75, 591 (2002)
S. Johansson & V.S. LetokhovAstrophysical lasers operating in optical Fe II lines in stellar ejecta of Eta CarinaeA&A 428, 497 (2004)
S. Johansson & V.S. LetokhovAstrophysical lasers operating in optical Fe II lines in stellar ejecta of Eta CarinaeA&A 428, 497 (2004)
S. Johansson & V.S. LetokhovAstrophysical lasers operating in optical Fe II lines in stellar ejecta of Eta CarinaeA&A 428, 497 (2004)
Quantum effects in cosmic light
Quantum effects in cosmic light
Laser effects inWolf-Rayet,
symbiotic stars,& novae
Sketch of the symbiotic star RW Hydrae
P. P. Sorokin & J. H. GlowniaLasers without inversion (LWI) in Space: A possible explanation for intense, narrow-band, emissions that dominate the visible and/or far-UV (FUV) spectra of certain astronomical objectsA&A 384, 350 (2002)
Raman scattered emission bands in the symbiotic star V1016 Cyg
H. M. SchmidIdentification of the emission bands at λλ 6830, 7088A&A 211, L31 (1989)
Quantum effects in cosmic light
Quantum effects in cosmic light
Emission fromneutron stars,
pulsars & magnetars
T.H. Hankins, J.S. Kern, J.C. Weatherall, J.A. EilekNanosecond radio bursts from strong plasma turbulence in the Crab pulsarNature 422, 141 (2003)
A. Shearer, B. Stappers, P. O'Connor, A. Golden, R. Strom, M. Redfern, O. RyanEnhanced Optical Emission During Crab Giant Radio Pulses Science 301, 493 (2003)
Mean optical “giant” pulse (with error bars) superimposed on the average pulse
V.A. Soglasnov et al.Giant Pulses from PSR B1937+21 with Widths ≤ 15 Nanoseconds and Tb ≥ 5×1039 K, the Highest Brightness Temperature Observed in the Universe, ApJ 616, 439 (2004)
Longitudes of giantpulses comparedto the average
profile.Main pulse (top);
Interpulse (bottom)
Coherent emission from magnetars
Coherent emission from magnetars
o Pulsar magnetospheres emit in radio;higher plasma density shifts magnetar emission to visual & IR (= optical emission in anomalous X-ray pulsars?)
o Photon arrival statistics (high brightness temperature bursts; episodic sparking events?). Timescales down to nanoseconds suggested (Eichler et al. 2002)
CO2 lasers on Mars
Spectra of Martian CO2 emission line as a function of frequency difference from line center (in MHz). Blue profile is the total emergent intensity in the absence of laser emission. Red profile
is Gaussian fit to laser emission line. Radiation is from a 1.7 arc second beam (half-power width) centered on Chryse Planitia. The emission peak is visible at resolutions R > 1,000,000.
(Mumma et al., 1981)
CO2 lasers on Earth
Vibrational energy states of CO2 and N2 associated with the natural 10.4 μm CO2 laserG.M. Shved, V. P. Ogibalov
Natural population inversion for the CO2 vibrational states in Earth's atmosphereJ. Atmos. Solar-Terrestrial Phys. 62, 993 (2000)
”Random-laser” emission”Random-laser” emission
A “random laser” of mm-sized spheres glows with laser-like light. Monochromatic flashes are initiated by a few “lucky” photons that remain inside the material for a
long time.D.Wiersma, Nature,406, 132 (2000)
Letokhov, V. S.Astrophysical LasersQuant. Electr. 32, 1065 (2002) = Kvant. Elektron. 32, 1065 (2002)
Masers and lasers in the active medium particle density -- medium dimension diagram
Quantum Optics @ TelescopesQuantum Optics @ Telescopes
Detectinglaser effects in
astronomical radiation
Intensity interferometryIntensity interferometry
Narrabri stellar intensity interferomer circa 1970 (R.Hanbury Brown, R.Q.Twiss et al., University of Sydney)
S.Johansson & V.S.LetokhovPossibility of Measuring the Width of Narrow Fe II Astrophysical Laser Lines in the Vicinity ofEta Carinae by means of Brown-Twiss-Townes Heterodyne Correlation Interferometryastro-ph/0501246, New Astron. 10, 361 (2005)
S.Johansson & V.S.LetokhovPossibility of Measuring the Width of Narrow Fe II Astrophysical Laser Lines in the Vicinity of Eta Carinae by means of Brown-Twiss-Townes Heterodyne Correlation Interferometryastro-ph/0501246, New Astron. 10, 361 (2005)
Expected dependence of the correlation signal as function of(a) heterodyne frequency detuning and (b) spacing of telescopes d
D. Dravins 1, C. Barbieri
2
V. Da Deppo 3, D. Faria
1, S. Fornasier 2
R. A. E. Fosbury 4, L. Lindegren
1
G. Naletto 3, R. Nilsson
1, T. Occhipinti 3
F. Tamburini
2, H. Uthas 1, L. Zampieri
5
(1) Lund Observatory(2) Dept. of Astronomy, Univ. of Padova
(3) Dept. of Information Engineering, Univ. of Padova(4) ST-ECF, ESO Garching
(5) Astronomical Observatory of Padova
HIGHEST TIME RESOLUTION, REACHING QUANTUM OPTICS
• Other instruments cover seconds and milliseconds
• QUANTEYE will cover milli-, micro-, and nanoseconds, down to the quantum limit !
Photon statistics of laser emissionPhoton statistics of laser emission
• (a) IfIf the light is non-Gaussian, photon statistics will be closer to stable wave(such as in laboratory lasers)
• (b) IfIf the light has been randomized andis close to Gaussian (thermal), photon correlation spectroscopy will reveal the narrowness of the laser light emission
Spectral resolution = 100,000,000 !
Spectral resolution = 100,000,000 !
o To resolve narrow optical laser emission (Δν 10 MHz) requires spectral resolution λ/Δλ 100,000,000
o Achievable by photon-correlation (“self-beating”) spectroscopy ! Resolved at delay time Δt 100 ns
o Method assumes Gaussian (thermal) photon statistics
Photon correlation spectroscopyPhoton correlation spectroscopy
E.R.Pike, in R.A.Smith, ed. Very High Resolution Spectroscopy, p.51 (1976)
LENGTH & TIME FOR SPECTROMETERS OF DIFFERENT RESOLVING POWER
Photon correlation spectroscopyPhoton correlation spectroscopy
E.R.Pike, in R.A.Smith, ed. Very High Resolution Spectroscopy, p.51 (1976)
LENGTH,TIME &FREQUENCYFORTWO-MODESPECTRUM
Photon correlation spectroscopyPhoton correlation spectroscopy
o Analogous to spatial informationfrom intensity interferometry,photon correlation spectroscopydoes not reconstruct the shape of
the source spectrum, but “only” gives linewidth information
SECONDS & MILLISECONDS
• Lunar & planetary-ring occultations• Rotation of cometary nuclei• Pulsations from X-ray pulsars• Cataclysmic variable stars• Pulsating white dwarfs• Optical variability around black holes• Flickering of high-luminosity stars• X-ray binaries• Optical pulsars• Gamma-ray burst afterglows
MILLI-, MICRO- & NANOSECONDS
• Millisecond pulsars ?• Variability near black holes ?• Surface convection on white dwarfs ?• Non-radial oscillations in neutron stars ?• Surface structures on neutron-stars ?• Photon bubbles in accretion flows ?• Free-electron lasers around magnetars ? • Astrophysical laser-line emission ?• Spectral resolutions reaching R = 100
million ?• Quantum statistics of photon arrival
times ?
John M. Blondin
(North Carolina State University)
Hydrodynamics on supercomputers:
Interacting Binary Stars
KUIPER-BELT OCCULTATION
S
Diffraction & shadow of irregular 1-km
Kuiper-belt object in front of a point star.
Horizontal axes in km, vertical axis is
stellar flux.
Grey central spot indicates the
geometrical shadow.
(Roques & Moncuquet, 2000)
PREVIOUS LIMITATIONS
* CCD-like detectors: Fastest practical frame rates: 1 - 10 ms
* Photon-counting detectors: Limited photon-count rates: ≳ 100 kHz
PRELIMINARY OPTICAL DESIGN
FEASIBILITY OF CONCEPT
* Slice OWL pupil into 100 segments
* Focus light from each pupil segment by one in an array of 100 lenses
* Detect with an array of 100 APD’s
Light collection with a lens array
Each lens has a square aperture, 10 mm side
The beam section is an annulus, with 100 mm external diameter
32x32 Single Photon Silicon Avalanche Diode Array Quantum Architecture Group, L'Ecole Polytechnique Fédérale de Lausanne
•
•
“ULTIMATE” DATA RATES
* 1024 x 1024 imaging elements @ 100 spectral & polarization channels
* Each channel photon-counting @ 10 MHz, 1 ns time resolution
* Data @ 1015 photon time-tags per second = 1 PB/s (Petabyte, 1015 B) = some EB/h (Exabyte = 1018 B)
•
•
“REALISTIC” DATA RATES
* 1024 x 1024 imaging elements one wavelength channel at a time
* Each channel photon-counting @ 10 MHz with 1 ns time resolution
* Data @ 1013 photon time-tags per second = 10 TB/s (Terabyte, 1012 B) ≈ 1 PB/min (Petabyte, 1015 B) ≈ 1 EB/few nights (Exabyte = 1018 B)
ROLE OF LARGE TELESCOPES
• VLT’s & ELT’s permit enormously more sensitive searches for high-speed phenomena in astrophysics
• Statistical functions of arriving photon stream increase with at least the square of the intensity
Advantages of very large telescopes
Advantages of very large telescopes
Telescope diameter
Intensity <I> Second-order correlation <I2>
Fourth-order photon statistics <I4>
3.6 m 1 1 1
8.2 m 5 27 720
4 x 8.2 m 21 430 185,000
50 m 193 37,000 1,385,000,000
100 m 770 595,000 355,000,000,000
•
•
INSTRUMENT DEVELOPMENT
* Lund Observatory: Laboratory setup of digital intensity interferometer
* Photon-counting APD’s, correlator time resolution 1.6 nanoseconds
* Simulated stellar observations with two “telescopes” observing a pinhole “star”
Photon Orbital Angular Momentum
Photon Orbital Angular Momentum
At microscopic level, interactions have been observedwith helical beams acting as optical tweezers.
A small transparent particle was confined away fromthe axis in the beam's annular ring of light.
The particle's tangential recoil due to the helical phasefronts caused it to orbit around the beam axis.
At the same time, the beam's spin angular momentumcaused the particle to rotate on its own axis.
M.Padgett, J.Courtial, L.Allen, Phys.Today May 2004, p.25
L.Velasco & A.Boardman, University of Salford, U.K.
An electromagnetic field is expressed as a scalar complex function; where the real and the imaginary parts of the field vanish, there is an optical singularity (also called dislocation for analogy with a crystal). This singularity can be either a screw dislocation or an edge-type.
The screw-type ones are optical vortices with a helicoidal wavefront.
Although polarization enables only two photon-spin states, photons can have many orbital-angular-momentum eigenstates, allowing single photons to encode much more information. Harwit, ApJ 597, 1266 (2003)
Spin
Photon Orbital Angular Momentum
POAM
Photon Orbital Angular Momentum
Photon Orbital Angular Momentum
M.Padgett, J.Courtial, L.Allen, Phys.Today May 2004, p.25
For any given l, the beam has l intertwined helical phase fronts.
For helically phased beams, thephase singularity on the axisdictates zero intensity there.
The cross−sectional intensity pattern of all such beams hasan annular character that persistsno matter how tightly the beamis focused.
Photon Orbital Angular Momentum
Photon Orbital Angular Momentum
* Individual photons can have different POAM states
* Imaging with POAM-manipulated lightmight reveal exoplanets
* Possible natural POAM sources?Rotating Kerr black holes??
Measuring Orbital Angular MomentumMeasuring Orbital Angular Momentum
Photon orbital angular momentumproduced by a spiral phase plate
Martin Harwit, ApJ 597, 1266 (2003)
Prototype POAM experiment with fork hologram
F.Tamburini, G.Umbriaco, G.Anzolin (Univ. of Padua, 2005)Thanks also to: Anton Zeilinger group,
Inst. of Experimental Physics, Univ. of Vienna
The first three orders: ℓ=0,1,2
l=2
l=1
l=0
F.Tamburini, G.Umbriaco, G.Anzolin (University of Padua, 2005)
F.Tamburini, G.Umbriaco, G.Anzolin , C.Barbieri, A.Bianchini (Padua), astro-ph/0505564
FrogEye, the Quantum Coronagraphic mask. The Photon Orbital Angular Momentum and its applications to Astronomy
Photonic astronomy !Photonic astronomy !
• [Almost] all our knowledge of the Universe arrives through photons
• Both individual photons and photon streams are more complex than has been generally appreciated
Quantum Optics @ ELT’s !Quantum Optics @ ELT’s !
• Quantum optics may open a fundamentally new information channel from the Universe !
• ELT’s will bring non-linear optics into astronomy !