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New tools for intensity interferometry New tools for intensity - - PowerPoint PPT Presentation

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Workshop on Stellar Intensity Interferometry January January 29 29- -30 30, , 2009 2009, Salt Lake City , Salt Lake City New tools for intensity interferometry New tools for intensity interferometry First experiment in intensity

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Workshop on Stellar Intensity Interferometry January January 29 29-

  • 30

30, , 2009 2009, Salt Lake City , Salt Lake City

New tools for intensity interferometry New tools for intensity interferometry

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SLIDE 2

First experiment in intensity interferometry

Hanbury-Brown &

Twiss 1954 Twiss 1954

Correlate detectors’

currents

2nd order correlation Measures only|γ12|

J d ll B k 1958

Measures only|γ12| Optical accuracy c/Δf

~ 30 cm

Insensitive to

atmosphere, optics

Jodrell Bank 1958 Narrabri 1969-74

p , p

New Tools for Intensity Interferometry New Tools for Intensity Interferometry Workshop on Stellar Intensity interferometry Workshop on Stellar Intensity interferometry

Erez Ribak Salt Lake City 2009

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SLIDE 3

What has changed in the world since 1974?

Amplitude interferometry, for one (and a big one, at that) But also

  • Telescopes: bigger phased panels adaptive optics

Telescopes: bigger, phased panels, adaptive optics

  • Electronics: the transform from analogue to digital
  • Optics: modulators, fibres, materials
  • Detectors
  • Computers
  • Data analysis: phase retrieval, speckle methods

y p , p All of these were used by amplitude interferometry Can we gain from them in intensity interferometry? Whi h i t i t it i t f t ? Which are unique to intensity interferometry?

New Tools for Intensity Interferometry New Tools for Intensity Interferometry Workshop on Stellar Intensity interferometry Workshop on Stellar Intensity interferometry

Erez Ribak Salt Lake City 2009

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Advances in technology

Light collectors are better, cheaper Photomultipliers out, avalanche photodiode arrays in … but analogue technology still has wider band width … but analogue technology still has wider band width Correlators up to109 bits/s in the radio, Čerenkov … but analogue technology still has wider band width New other tools

  • Non-imaging light concentrators
  • Long-haul fibre optics (single- and multimode)

g p ( g )

  • Other optical paraphernalia: spectrometers, correlators
  • Global positioning systems

C l t t l t (di it l i )

  • Correlators on computer clusters (digital again)

New Tools for Intensity Interferometry New Tools for Intensity Interferometry Workshop on Stellar Intensity interferometry Workshop on Stellar Intensity interferometry

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Advances in performance: technology

bν = electronic bandwidth α = quantum efficiency Σ = system efficiency

A Ofir thesis

Σ = system efficiency m = optical channels bν → 1GHz, α → 0.8, Σ → 0.8, m=1 4 99 NSII performance: 0m star, 1 hr, SNR=27 bν = 100MHz, α = 0.2, Σ = 0.2, m = 1 4.99 4.91

New Tools for Intensity Interferometry New Tools for Intensity Interferometry Workshop on Stellar Intensity interferometry Workshop on Stellar Intensity interferometry

Erez Ribak Salt Lake City 2009

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telescopes

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Advances in theory

M l ti (F t 1983)

  • More correlations (Fontana 1983)
  • Higher order correlations
  • Parallel spectral detectors

Source

  • Correlators on computer clusters
  • Triple correlation
  • Adds phase information

Square Law Detectors Amplifiers D1 D2 D3 Dk Dn A1 An A2 A3 Ak … …

  • Proposed by Gamo (1963)
  • Demonstrated in lab (Sato 1978)
  • Applied in speckle interferometry

Delays τ1 τn τ2 τ3 τk … … M

Applied in speckle interferometry (Weigelt, Lohmann 1980s)

  • Use zero sheets in the Fourier domain
  • 1-d polynomials (Bates 1984)

Multiplier Integrator M I

1 d polynomials (Bates 1984)

  • Cauchy-Riemann equations

(Holmes 2008)

Recorder R

New Tools for Intensity Interferometry New Tools for Intensity Interferometry Workshop on Stellar Intensity interferometry Workshop on Stellar Intensity interferometry

Erez Ribak Salt Lake City 2009

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Advances in performance: high-order correlations

A Ofir thesis

Quintuplets Sextuplets N=57 Septuplets N=71 Octuplets N=85 Nonuplets N=99

most improvement

Triplets Quadruplets N=29 Q p N=43 T i l t

most improvement for sharp-contrast

  • bjects (high V )

N=15 Triplets N=54 Triplets Triplets N=210 Scaling from NSII performance (<1972) Triplets N=3335 New Tools for Intensity Interferometry New Tools for Intensity Interferometry Workshop on Stellar Intensity interferometry Workshop on Stellar Intensity interferometry

Erez Ribak Salt Lake City 2009

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Laboratory experiment

Bl LED

  • Blue LEDs
  • Sheltered light path, light baffles
  • Telescopes: Fresnel lenses a few meters away
  • Fast photomultipliers at Fresnel foci

LED spectrum p p LED spectrum F l ll Fresnel collector

New Tools for Intensity Interferometry New Tools for Intensity Interferometry Workshop on Stellar Intensity interferometry Workshop on Stellar Intensity interferometry

Erez Ribak Salt Lake City 2009

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Lipson and Spektor (work in progress)

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Laboratory communication and correlation

  • Fast electronics using current technologies (e.g. optical coupler)
  • Employing RF gain/phase detector as phase difference element
  • Analogue function

g

  • Slight frequency deterioration
  • Up to 2.7 GHz

New Tools for Intensity Interferometry New Tools for Intensity Interferometry Workshop on Stellar Intensity interferometry Workshop on Stellar Intensity interferometry

Erez Ribak Salt Lake City 2009

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Implemenetation

Ph diff l

  • Phase difference element
  • Wide frequency range: 0.1→1GHz (local radio stations → PMT limit)
  • Unfortunately device requires frequency to find phase
  • Used only to work at zero phase difference (zero delay)

y p ( y)

  • First successful results obtained
  • With signal, noise level rises as expected
  • Higher correlation

New Tools for Intensity Interferometry New Tools for Intensity Interferometry Workshop on Stellar Intensity interferometry Workshop on Stellar Intensity interferometry

Erez Ribak Salt Lake City 2009

no signal with signal

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Formation flight

Space

k

Formation flight

Calculation of orbits

requiring minimal fuel P F i

source

kx ky

Proper Fourier coverage Simple collectors UV-blue coverage y

kx

Data handling Transmit photon events Space/ground correlators

ky

Space/ground correlators

source

kx

source

ky Orbits Fourier coverage Klein, Guellman, Lipson, 2007

New Tools for Intensity Interferometry New Tools for Intensity Interferometry Workshop on Stellar Intensity interferometry Workshop on Stellar Intensity interferometry

Erez Ribak Salt Lake City 2009

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O b ts ou e cove age Klein, Guellman, Lipson, 2007

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M di ( 20 ) ll bi ld l bj

Antarctica

Medium (~20m) collectors: bigger would resolve objects Can be used for coronagraphy (resolve star, not planet) Many base lines: simultaneity not so important for closure, but… Many (n>50) collectors: improvement in SNR ~n1.1 for high γ UV-Vis: complement amplitude interferometry in IR

Presented at 2nd ARENA Workshop on Interferometry 2008 New Tools for Intensity Interferometry New Tools for Intensity Interferometry Workshop on Stellar Intensity interferometry Workshop on Stellar Intensity interferometry

Erez Ribak Salt Lake City 2009

12 Presented at 2nd ARENA Workshop on Interferometry, 2008

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Setting up array observatories

λ surface, delay accuracy diameter array area

  • no. of

elements focal position signal handling lunar in- terference synergy

µm µm m km Čerenkov detection 0.3-1 100 5-25 1×1 10-100 below focus cross- correlate high IceCube radio interferometry 500+ 100 5-25 1×1 10-100 focus, chopper cross- correlate low IceCube interferometry chopper correlate intensity interferometry 0.3-1 100 5-25 1×1 10-100 focus cross- correlate high

  • li

d 0 7 10 0 1 0 5 1 1 5 20 f i f l amplitude interferometry 0.7-10 0.1 0.5 or 8-10+AO 1×1 5-20 focus, chopper interfere

  • ptically

low

  • All values are negotiable
  • The first three arrays share many parameters
  • Some optics can be shared, electronics less so
  • Planning and designing a common array is essential for funding

New Tools for Intensity Interferometry New Tools for Intensity Interferometry Workshop on Stellar Intensity interferometry Workshop on Stellar Intensity interferometry

Erez Ribak Salt Lake City 2009

13 Presented at 2nd ARENA Workshop on Interferometry, 2008

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F l l i f h l i li d

Sharing collectors with Čerenkov detectors

  • Focal plane camera is an array of photomultiplier detectors
  • Spot size (PSF) is relatively large, for parabolic collectors or Davies-Cotton
  • Addition of nearby detector signals encouraged
  • Better still: use cross detectors for spectral dispersion

p p

New Tools for Intensity Interferometry New Tools for Intensity Interferometry Workshop on Stellar Intensity interferometry Workshop on Stellar Intensity interferometry

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L l i f

Sharing telescopes with amplitude interferometry

  • Large telescope interferometers
  • Very Large Telescope Interferometer: 4×8m (+ 4×2m)
  • Keck Interferometer: 2×10m
  • (Narrabri: 2×6.5m)

( )

  • Adaptive optics correction
  • Visible source for reference
  • Transfer of infra-red beams to combiner, interference

> 90% f i ibl li ht t d

  • > 90% of visible light not used
  • Can be employed for simultaneous intensity interferometry
  • Employ fastest detectors (10 GHz?)
  • Correlate all with all (6 at VLTI, 2 at KI)
  • Use spectrometer to separate to m ~100 channels (flux permitting)
  • Parallel correlations for all m channels
  • UV coverage better than amplitude interferometry (and higher resolution)
  • All measurements are simultaneous (but different λ→different baselines)
  • All measurements are simultaneous (but different λ→different baselines)

New Tools for Intensity Interferometry New Tools for Intensity Interferometry Workshop on Stellar Intensity interferometry Workshop on Stellar Intensity interferometry

Erez Ribak Salt Lake City 2009

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  • New devices convert input light to modulation of laser light

Fibre ring

  • New devices convert input light to modulation of laser light
  • Evanescent light coupling from IR laser beam in light guide into ring
  • Ring resonance depending on size
  • Coupling back, transmission drops to zero on main beam

polysilicon laser

  • Work by Michal Lipson and group at Cornell EE

New Tools for Intensity Interferometry New Tools for Intensity Interferometry Workshop on Stellar Intensity interferometry Workshop on Stellar Intensity interferometry

Erez Ribak Salt Lake City 2009

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  • Now we illuminate the device

All optical modulation

  • Now we illuminate the device
  • Ring resonance depending on size but also on plasma dispersion
  • Free carriers from blue pump beam modify plasma
  • Resonance shifts, changes absorbed wave length
  • Switching energy 535×10-15 J/bit = 1×106 photons/bit for 10 dB modulation

420 nm transmission 1568 nm pump beam probe beams pump beam

New Tools for Intensity Interferometry New Tools for Intensity Interferometry Workshop on Stellar Intensity interferometry Workshop on Stellar Intensity interferometry

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Optical to optical conversion and correlation

  • Send same laser beam to all dishes
  • Send same laser beam to all dishes
  • Stellar light to laser modulation

a AND b a AND b

  • If ring too small, add many such rings

a NAND b

If ring too small, add many such rings

  • Amplify laser beams, if needed (EDFA)
  • Divide into parallel channels
  • Correlate laser signals from other dishes

New Tools for Intensity Interferometry New Tools for Intensity Interferometry Workshop on Stellar Intensity interferometry Workshop on Stellar Intensity interferometry

Erez Ribak Salt Lake City 2009

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System view (vision?)

  • Send same laser beam to all dishes
  • Send same laser beam to all dishes
  • Stellar light to laser intensity modulation
  • If ring too small, add many such rings
  • Add baseline delays, as in radio interferometry

delays lines

  • Amplify laser beams, if needed
  • Divide into parallel channels
  • Correlate laser signals from other dishes

laser lifi detectors ω1 ω2 amplifiers frequency modulators amps amps

1 2 1 2

2 cos I I I I t ω + + Δ

  • All-fibre technology

New Tools for Intensity Interferometry New Tools for Intensity Interferometry Workshop on Stellar Intensity interferometry Workshop on Stellar Intensity interferometry

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beam combination

1 2 1 2

All fibre technology

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Astrophysics in one or more bands, synergies

  • Studies of jets (galaxies AGNs supernovae)
  • Studies of jets (galaxies, AGNs, supernovae)
  • Point sources at most wave lengths, fast changes of intensity, spectrum
  • Persistent claims by de Rujula and Dar:
  • Identification of γ-ray bursts with supernovae
  • Successive, relativistic plasma bullets look like jets
  • Spectra and intensity depend strongly on directionality
  • Successful prediction of every afterglow event
  • Identification of γ-ray sources (last scatter?)

Identification of γ ray sources (last scatter?)

  • Origin of cosmic rays, directionality, GZK limit
  • Opposing theories for GRB: clashes between shells of ejecta
  • Difficulty: weak signals, unresolvable objects

Ad l GRB i b lli

  • Advantage: early GRB warning by satellites
  • Interesting for Čerenkov, mm-wave and intensity interferometry

New Tools for Intensity Interferometry New Tools for Intensity Interferometry Workshop on Stellar Intensity interferometry Workshop on Stellar Intensity interferometry

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Thank you Thank you for your attention

Special thanks to D. Kieda and S. LeBohec

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who made this visit possible