From Wikipedia, the free encyclopedia Electromagnetically induced transparency
Electromagnetically induced transparency
The effect of EIT on a typical absorption line. A weak probe
normally experiences absorption shown in blue. A second cou-
pling beam induces EIT and creates a "window" in the absorp-
tion region (red). This plot is a computer simulation of EIT in
an InAs/GaAs quantum dot EIT level schemes can be sorted into three categories; vee, lad-
der, and lambda.
Electromagnetically induced transparency (EIT) is a
coherent optical nonlinearity which renders a medium tical fields. The three types of EIT schemes are differenti-
transparent over a narrow spectral range within an ab- ated by the energy differences between this state and the
sorption line. Extreme dispersion is also created within other two. The schemes are the ladder, vee, and lamb-
this transparency "window" which leads to "slow light", da. Any real material system may contain many triplets
described below. of states which could theoretically support EIT, but there
Observation of EIT involves two optical fields (highly are several practical limitations on which levels can actu-
coherent light sources, such as lasers) which are tuned ally be used.
to interact with three quantum states of a material. The Also important are the dephasing rates of the individ-
"probe" field is tuned near resonance between two of the ual states. In any real system at finite temperature there
states and measures the absorption spectrum of the tran- are processes which cause a scrambling of the phase of
sition. A much stronger "coupling" field is tuned near the quantum states. In the gas phase, this means usually
resonance at a different transition. If the states are se- collisions. In solids, dephasing is due to interaction of the
lected properly, the presence of the coupling field will electronic states with the host lattice. The dephasing of
create a spectral "window" of transparency which will be state |3> is especially important, ideally |3> should be a
detected by the probe. The coupling laser is sometimes robust, metastable state.
referred to as the "control" or "pump", the latter in anal- Current EIT research uses atomic systems in dilute
ogy to incoherent optical nonlinearities such as spectral gasses, solid solutions, or more exotic states such as Bose-
hole burning or saturation. Einstein condensate. Work is also being done in semicon-
EIT is based on the destructive interference of the ductor nanostructures such as quantum wells, quantum
transition probability between atomic states. Closely re- wires and quantum dots.
lated to EIT are coherent population trapping (CPT) phe-
nomena. EIT is a coherently prepared media which has
long quantum memory
Theory
EIT was first proposed theoretically by professor Jakob
Material requirements Khanin and graduate student Olga Kocharovskaya at
Gorky State University (present: Nizhnij Novgorod), Rus-
There are specific restrictions on the configuration of the sia [1]; there are now several different approaches to a
three states. Two of the three possible transitions be- theoretical treatment of EIT. One approach is to extend
tween the states must be "dipole allowed", i.e. the tran- the density matrix treatment used to derive Rabi oscil-
sitions can be induced by an oscillating electric field. The lation of a two-state, single field system. In this picture
third transition must be "dipole forbidden." One of the the probability amplitude for the system to transfer be-
three states is connected to the other two by the two op-
1
From Wikipedia, the free encyclopedia Electromagnetically induced transparency
tween states can interfere destructively, preventing ab- refractive index produces an extremely low group veloc-
sorption. In this context, "interference" refers to inter- ity. See for this the comprehensive review on this subject
ference between quantum events (transitions) and not op- in.[1] The first experimental observation of the low group
tical interference of any kind. As a concrete example, velocity produced by EIT was by Boller, Imamoglu, and
consider the lambda scheme shown above. Absorption of Harris at Stanford University in 1991 in strontium. The
current record for slow light in an EIT medium is held by
the probe is defined by transition from to . The
Budker, Kimball, Rochester, and Yashchuk at U.C. Berke-
fields can drive population from - directly or from ley in 1999. Group velocities as low as 8 m/s were mea-
- - - . The probability amplitudes for the dif- sured in a warm thermal Rubidium vapor.[2]
Stopped light, in the context of an EIT medium, refers
ferent paths interfere destructively. If has a compar- to the coherent transfer of photons to the quantum sys-
atively long lifetime, then the result will be a transparent tem and back again. In principle, this involves switching
window completely inside of the - absorption line. off the coupling beam in an adiabatic fashion while the
Another approach is the "dressed state" picture, probe pulse is still inside of the EIT medium. There is
wherein the system + coupling field Hamiltonian is diag- experimental evidence of trapped pulses in EIT medium.
onalized and the effect on the probe is calculated in the In [3] authors created stationary light pulse inside the
new basis. In this picture EIT resembles a combination of atomic coherent media. In 2009 researchers from Har-
Autler-Townes splitting and Fano interference between vard University and MIT demonstrated few-photon op-
the dressed states. Between the doublet peaks, in the cen- tical switch for quantum optics based on the slow light
ter of the transparency window, the quantum probability ideas [4]
amplitudes for the probe to cause a transition to either
state cancel.
A polariton picture is particularly important in de-
See also
scribing stopped light schemes. Here, the photons of the • Atomic coherence
probe are coherently "transformed" into "dark state po- • Electromagnetically Induced Grating
laritons" which are excitations of the medium. These ex-
citations exist (or can be "stored") for a length of time de- References
pendent only on the dephasing rates.
[1] Matsko A.B., Kocharovskaya O., Rostovtsev Y.,
Welch G.R., Zibrov A.S., Scully M.O., "Slow,
Slow light and stopped light ultraslow, stored, and frozen light", ADVANCES IN
ATOMIC, MOLECULAR, AND OPTICAL PHYSICS, VOL
46, 191-242, (2001)
[2] D. Budker, D. F. Kimball, S. M. Rochester, and V. V.
Yashchuk, "Nonlinear Magneto-optics and Reduced
Group Velocity of Light in Atomic Vapor with Slow
Ground State Relaxation", Phys. Rev. Lett. 83, pg.
1767-1770 (1999)
[3] Bajcsy M, Zibrov A.S, Lukin M.D., "Stationary pulses
of light in an atomic medium", NATURE, 426 426,
638-641, (2003)
[4] Bajcsy M , Hofferberth S, Balic V, Peyronel T, Hafezi
M , Zibrov A.S , Vuletic V , Lukin M.D., "All-Optical
Switching Using Slow Light within a Hollow Fiber",
102,
Phys. Rev. Lett., 102 20390, (2009)
Rapid change of index of refraction (blue) in a region of rapidly
changing absorption (gray) associated with EIT. The steep and Primary work
positive linear region of the refractive index in the center of the
• O.Kocharovskaya, Ya.I.Khanin, Sov. Phys. JETP, , p945
transparency window gives rise to slow light
(1986)
• K.J. Boller, A. Imamoglu, S.E. Harris, Physical Review
It is important to realize that EIT is only one of many
Letters , p2593 (1991)
diverse mechanisms which can produce slow light. The
• Eberly, J. H., M. L. Pons, and H. R. Haq, Phys. Rev.
Kramers–Kronig relations dictate that a change in ab-
Lett. , 56 (1994)
sorption (or gain) over a narrow spectral range must be
• D. Budker, D. F. Kimball, S. M. Rochester, and V. V.
accompanied by a change in refractive index over a sim-
Yashchuk, Physical Review Letters, , p1767 (1999)
ilarly narrow region. This rapid and negative change in
2
From Wikipedia, the free encyclopedia Electromagnetically induced transparency
• Lene Vestergaard Hau, S.E. Harris, Zachary Dutton, • Zachary Dutton, Naomi S. Ginsberg, Christopher
Cyrus H. Behroozi, Nature v.397, p594 (1999) Slowe, and Lene Vestergaard Hau (2004) The art of
• D.F. Phillips, A. Fleischhauer, A. Mair, R.L. taming light: ultra-slow and stopped light.
Walsworth, M.D. Lukin, Physical Review Letters , Europhysics News Vol. 35 No. 2
p783 (2001) • M. Fleischhauer, A. Imamoglu, and J. P. Marangos
• Naomi S. Ginsberg, Sean R. Garner, Lene Vestergaard (2005), "Electromagnetically induced transparency:
Hau, Nature , 623 (2007) Optics in Coherent Media", Reviews Modern Physics,
77,
77 633
Review
• Harris, Steve (July, 1997). Electromagnetically Сriticism
Induced Transparency. Physics Today, 50 (7), • Evgenii B Aleksandrov and Valerii S Zapasskii Phys.-
pp. 36–42 (PDF Format) 47,
Usp. "[2]" 47 1033 (2004)
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Categories:
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• Quantum mechanics
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