Electromagnetically Induced Transparency (EIT)physics.wm.edu/~inovikova/phys404/lecturenotes/... ·...

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Transcript of Electromagnetically Induced Transparency (EIT)physics.wm.edu/~inovikova/phys404/lecturenotes/... ·...

  • Electromagnetically Induced

    Transparency (EIT)

    b〉c〉

    a〉 γ γ

    EC EP

    D〉B〉

    a〉 γ γ

    Bright and dark states:

    Atomsdo not “see” light!2

    P2C EE +

    2C

    2P

    CP

    EE

    cEbEB

    +

    +=

    2C

    2P

    PC

    EE

    cEbED

    +

    −=

  • Electromagnetically Induced

    Transparency (EIT)

    b〉c〉

    a〉 γ γ

    EC EP

    δ

    Tran

    smis

    sion

    δProbe frequency

    Width of EIT peak is determined by control field intensity , but limited by spin coherence lifetime

  • Slow light via Electromagnetically

    Induced Transparency (EIT)R

    efra

    ctiv

    e in

    dex

    Probe frequency

    Tran

    smis

    sion

    1ddn >>

    ωω

    Steep dispersion

    Narrow transmission resonance

    LN

    1E2

    2C

    EITλγ

    ∝γ

  • Group velocity manipulation

    Ele

    ctric

    fiel

    d

    Light propagation direction

    Group velocity

    ωω+

    =ω=

    ddn

    n

    cdk

    )k(dvg

  • Group velocity manipulation

    Group velocity

    ωω+

    =ω=

    ddn

    n

    cdk

    )k(dvg

    “Slow” light

    1ddn >>

    ωω vg

  • Group velocity manipulation

    Group velocity

    ωω+

    =ω=

    ddn

    n

    cdk

    )k(dvg

    “Fast” light

    0ddn <

    ωω vg>c or vg

  • Group velocity manipulation

    Eugeniy E. Mikhailov, Vladimir A. Sautenkov, Irina Novikova, and George R. WelchPhys. Rev. A 69, 063808 (2004)

  • Slow light in EITR

    efra

    ctiv

    e in

    dex Steep dispersion in EIT

    means controllableslow group velocity

    Probe frequency

    Tran

    smis

    sion

    γλπ∝

    2C

    2g

    EN38

    v

    Group velocity

    0ddn >>

    ωω

    What happens when control field goes to zero?

  • Coupling of a probe pulse and a spin

    wave

    b〉c〉

    a〉 γ γ

    EC

    Dark state:

    2C

    2P

    PC

    EE

    cEbED

    +

    −=

    b〉c〉

    a〉 γ γ

    EC EP

  • Light-atoms interaction:

    dark-state polariton

    bcP ˆNsinÊcosˆ σθ−θ=Ψ

    Cg E

    c

    vcos ∝=θ

    Photons of the probe field

    Excitations of the spin wave

    M. Fleischhauer and M.D. LukinPRL 84, 5094 (2000)

    θ−θ=Ψ sincosˆ

  • Quantum memory for photons

    γαΩ

    =2

    2v g

    Ideal memory operation

  • How long does the dark state live?

    Cold atoms

    No Doppler broadening, butthere may be difficulties due to - uncompensated magnetic

    fields- gravity- insufficient number of atoms- collisions between atoms

    These are technical problems – if all are fixed, the ground state coherence was shown to live up to several seconds!

  • How long does the dark state live?

    atoms fly away !

    With buffer gas

    No buffer gas Tva

    t =a

    with anti-relaxation coating

    vT ≈ 400m/s Rb cell

  • How long does the dark state live?

    With buffer gaswith anti-relaxation coating

    0 2.5 5−2.5−50.1

    0.2

    0.3

    0.4

    0.5

    0.6

    Two−photon detuning Ω (MHz)

    Nor

    mal

    ized

    tran

    smis

    sion