guided acoustic wave brillouin scattering (gawbs) …...inst. of optics, information & photonics...

Inst. of Optics, Information & Photonics (MPReserach Group), Dep. 1: Prof. Leuchs, Quantum Information Processing Group

Guided Acoustic Wave Brillouin Scattering (GAWBS)in Photonic Crystal Fibers (PCFs)

FRISNO-9

Dominique Elser

15/02/2007

Guided Acoustic Brillouin Wave Scattering in Photonic Crystal Fibers

Page 1Inst. of Optics, Information & Photonics (MPReserach Group), Dep. 1: Prof. Leuchs, Quantum Information Processing Group

Les Houches, 18.02.2007

GAWBS Theory

Thermally excited acoustic fiber vibrations at certain resonancefrequencies scatter light due to

i) modulation of refractive index (photoelastic effect)ii) transversal acoustic phonons

Conservation ofenergy:

momentum:

incidentphoton

scatteredphoton

phonon

fiber

transversal phonons if




Acoustic Modes in Standard Fibers

R. M. Shelby, M. D. Levenson, and P. W. Bayer, Phys. Rev. Lett. 54, 939 (1985).

R0,0R0,3 TR2,0TR2,5

Mixed torsional-radial modes TR2,m induce phase and polarization noise (by generating birefringence in the fiber).

TR4,0

Radial modes R0,m induce phase noise by modulating the refractive index.




Investigated Fibers

NL-PM-700Crystal Fibre

highly reduced up to 200MHz

highly reduced up to 200MHz

not visible

about to be measured

Phase noise

Polarization noise

Amplitude noise

Quantum noise reduction

FS-PM-46113M

discrete peaks over whole measured frequency spectrum

5.1dB polarization squeezingin FS-PM-7811


not visible

HB800GFibercore



not visible

not measured

PM–NL–3.0–850Crystal Fibre

partly reduced up to 500MHz, enhanced above

partly reduced up to 500MHz, enhanced above

high peak at 53MHz

1.7dB polarization squeezing inPM-NL-800

Lucent fiber

reduced up to 250MHz

1.7dB amplitude squeezing by spectral filtering

not measured

not measured

Highly birefringent #2N. Joly, Ph. Russell

reduced below 190MHz, enhanced above

not measured

not measured

not measured

Highly birefringent #9N. Joly, Ph. Russell

reduced below 75MHz, enhanced above 300MHz

several peaks between 90 and 380 MHz

not measured

not measured

PM-1550-01Crystal Fibre

enhanced between 500 and 800MHz

enhanced between 250 and 800MHz

to be investigated

not measured

Standard Fibers Photonic Crystal Fibers (PCFs)

modify acoustic spectrum by spatial structuring (phononic crystal)




Phase Noise Measurement Setup




Polarization Noise Measurement Setup




Phase Noise Measurements

solid line:

dashed line:std. fiber

R0,m-modes




Polarization Noise Measurements

solid line:

dashed line:std. fiber

TR2,m-modes




Acoustic Simulations

Specifications:geometry: infinitely long cylinder with cross sectionboundary conditions: freematerial: silica glass (E, ν, ρ)model: plane strain eigenfrequency analysis

with small displacements

Equations:

Result: frequency and displacements for every mode

Normalization: total vibrational energy for each mode (equipartition theorem)




Optical Simulations

Specifications:wavelength, refractive indexboundary conditions: continuity of tangential components at holesmodel: perpendicular hybrid mode analysis

Equations: assume:

Result: effective index and electric field for the fundamental mode




Light-Sound Coupling

Strain-optical effect (photoelastic effect)

Phase noise:phase shift:

forward scattering efficiency:

Polarization noise:phase shift difference:

forward scattering efficiency:




Phase Noise Simulation of Std. Fiber




Cross Section Plots




Polarization Noise Sim. of Std. Fiber




Simulation of Phase Noise in PCF




Radial Cladding Modes




Cross Section Plots

Δn for standard fiberΔn for PCF

light field in PCF




Quasi-radial Hole Structure Modes




Simulation of Polarization Noise in PCF




Core Vibrations

J. Beugnot, T. Sylvestre, H. Maillotte, G. Mélin, and V. Laude

“Guided acoustic wave Brillouin scatteringin photonic crystal fibers”Optics Letters 32, 17 (2007)




Conclusion and Outlook

Acoustic spectrum of fibers can be modified by spatial structuring

Reduction of noise in broad frequency rangeimprove squeezing and quantum state transmission

Investigate cladding-less fibers

Tailor structure to also reduce high frequency noise

Include longitudinal phonon components and damping in simulations

guided acoustic wave brillouin scattering (gawbs) …...inst. of optics, information & photonics...

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