Report on an innovative all-optical spectrum analyzer.

1. Photonic-chip-based RF
spectrum analyzer
Raphael BouskilaRaphael Bouskila

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OutlineOutline
 IntroductionIntroduction
 WaveguideWaveguide
 RF spectrum analyzerRF spectrum analyzer
 ConclusionConclusion

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IntroductionIntroduction

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WaveguideWaveguide
 Amount of nonlinearity dependent onAmount of nonlinearity dependent on
intensity:intensity:
 Fiber core diameter: ~8-10Fiber core diameter: ~8-10 μμmm
– Effective area: ~50-80Effective area: ~50-80 μμmm22
2
eff
2 n
A
π
γ
λ
=

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WaveguideWaveguide
 Second problem: DispersionSecond problem: Dispersion
– N.B.N.B. DD == DDWGWG ++ DDmatmat

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WaveguideWaveguide
 What to do?What to do?
 Solution: Ridge (or rib) waveguideSolution: Ridge (or rib) waveguide

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WaveguideWaveguide
 High nonlinearityHigh nonlinearity
achieved via extremelyachieved via extremely
high mode confinementhigh mode confinement
– AAeffeff: 2.61: 2.61 μμmm22
 Low dispersionLow dispersion
achieved byachieved by
compensatingcompensating DDmatmat withwith
DDWGWG

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WaveguideWaveguide
 When they say “wide bandwidth,” theyWhen they say “wide bandwidth,” they
aren’t kidding:aren’t kidding:

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RF spectrum analyzerRF spectrum analyzer
 Regular PSD:Regular PSD:
 RF spectrum:RF spectrum:
 Used to characterize sources andUsed to characterize sources and
components; provides information aboutcomponents; provides information about
distortions and nonidealitiesdistortions and nonidealities
2
( ) ( ) i t
S E t e dtω
ω = ∫
22
( ) ( ) i t
RFS E t e dtω
ω = ∫

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RF spectrum analyzerRF spectrum analyzer
 Typically done using expensiveTypically done using expensive
electronicselectronics
 All-optical method preferred!All-optical method preferred!

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RF spectrum analyzerRF spectrum analyzer

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RF spectrum analyzerRF spectrum analyzer

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ConclusionConclusion
 Advantages:Advantages:
– Ultrawide bandwidthUltrawide bandwidth
– Record-setting nonlinearityRecord-setting nonlinearity
– Low dispersionLow dispersion
 Limitations:Limitations:
– Material and fabrication costsMaterial and fabrication costs
– Dispersion could be minimized furtherDispersion could be minimized further

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ReferencesReferences
 [1] M. Pelusi[1] M. Pelusi et al.et al. Photonic-chip-based radio-Photonic-chip-based radio-
frequency spectrum analyser with terahertzfrequency spectrum analyser with terahertz
bandwidth.bandwidth. Nature PhotonicsNature Photonics 33, 139-143 (March, 139-143 (March
2009).2009).
 [2] B. E. A. Saleh & M. C. Teich. Fundamentals[2] B. E. A. Saleh & M. C. Teich. Fundamentals
of Photonics, 2nd ed. Wiley, 2007.of Photonics, 2nd ed. Wiley, 2007.
 [3] G. P. Agrawal. Nonlinear Fibre Optics, 4th[3] G. P. Agrawal. Nonlinear Fibre Optics, 4th
ed. Academic Press, 2006.ed. Academic Press, 2006.
 [4] M. R. E. Lamont[4] M. R. E. Lamont et al.et al. Dispersion engineeringDispersion engineering
of highly nonlinear As2S3 waveguides forof highly nonlinear As2S3 waveguides for
parametric gain and wavelength conversion.parametric gain and wavelength conversion.
Opt. ExpressOpt. Express 1515, 9458–9463 (2007)., 9458–9463 (2007).