pre-excitation of rb atoms by frequency chirped laser pulses for efficient plasma generation
DESCRIPTION
Pre-excitation of Rb atoms by frequency chirped laser pulses for efficient plasma generation. G.P. Djotyan Wigner Centre for Physics of the Hungarian Academy of Sciences Contributors: D. Dzsotjan Zs. S örlei J. Bakos G. Demeter - PowerPoint PPT PresentationTRANSCRIPT
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Pre-excitation of Rb atoms by frequency chirped laser pulses for efficient plasma generation
G.P. DjotyanWigner Centre for Physics of the Hungarian Academy of Sciences
Contributors: D. Dzsotjan Zs. Sörlei J. Bakos G. Demeter N. Sandor
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Outline
Frequency chirped laser pulses and their application in manipulation of inner and translational states of multilevel atoms: some results achieved in the field in the Wigner Centre
Robust pre-excitation of Rb atoms by frequency chirped ultra-short laser pulses for efficient OBI or impact ionization
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Over-barrier and impact ionization of excited Rb atoms
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Action of a laser pulse with area A = ∫ Ω(t) dt = 5 π
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Action of a frequency-chirped laser pulse on a two-level atom
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Coherent Population Transfer to a Target State Without Excitation of the Atom:
Interaction of a single frequency chirped laser pulse with L –atom
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Dynamics of the populations of the L-atom in the field of single “narrowband” frequency-chirped laser pulse
n2
n3
n1
-3 -2 -1 0 1 2 3TIME
0
0.2
0.4
0.6
0.8
1
SNOITALUPOP
n1
n3n2
G.P. Djotyan, J.S. Bakos, Zs. Sörlei, J.Szigeti, Phys.Rev.A, 70, 063406 (2004)
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Creation of superposition between a ground and excited state
G.P. Djotyan, N. Sandor, J.S. Bakos, Zs. Sörlei, Opt. Express, 19, n. 18, 17493(2011)
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Electromagnetically self-induced transparency of a single narrowband frequency-chirped laser pulse
The propagation distance X is measured in the units of the absorption lengthG. Demeter, D. Dzsotjan, and G. P. Djotyan.
Phys.Rev.A, 76, 023827 (2007)
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Using frequency-chirped pulses in manipulation of translational states of atoms
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Experiment: Momentum transfer to Rb atoms by partially overlapping laser pulses
J.S. Bakos, G.P. Djotyan, et al., Eur. Phys. J. D, 39, 59 (2006);
Eur. Phys. J. D 44, 149 (2007)
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Population transitions in Rb85 atom (D2 line) induced by frequency-chirped laser pulses
GP. Djotyan, JS. Bakos, G. Demeter, PN. Ignacz, MA. Kedves, Zs. Sorlei, J. Szigeti, Z.Toth, Phys.Rev A, 68, 053409 (2003)
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Parameters of the MOT and of the trapped and cooled atomic cloud
• Volume ~ 1 mm3
• Number of atoms ~ 10 7
• Lifetime ~ 500 msec• Temperature ~ 10 -100 μK
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Rb transition lines and the ionization scheme
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Dynamics of the populations for positive and negative frequency chirp
I0>
I1>
I2>
I3>I4>
I5>
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Final populations of the ground state 5s and first excited state
5s
5p
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Final populations of the excited states 5d and 7s
5d 7s
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ConclusionsFrequency chirped laser pulses may be successfully applied for pre-excitation of Rb atoms before further one-photon or over the barrier ionization by a strong laser pulse, or by the impact ionization. The pre-excitation of a gas of Rb atoms will drastically diminish the threshold of the ionization. Advantages of using frequency chirped laser pulses:i. Robustness of the atomic population transfer against variation of parameters of the laser radiationii. Applicability in both homogeneously and in-homogeneously broadened media, e.g. hot vapors (Doppler-broadening) or solid-state environmentii. Ability to select a target state even in the case of broadband (e.g. ultra-short) laser pulses in the case of spectrally non-resolved manifold of atomic (molecular) energy levels.
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Our plans in the field of the theory of laser plasma generation:
-Atomic physics: numerical simulations of interaction of multilevel atoms with ultra-short and intense laser pulses, including ones with phase modulation. Analysis and simulation of different regimes of ionization, including resonance-enhanced multi-photon, tunneling, OBI and impact ionization.
-Simulation of propagation and nonlinear interaction of intense laser pulses in highly nonlinear resonant multi-level atomic media, including pulses with frequency modulation, electromagnetically induced transparency regime, etc.
- At special interest: Propagation and nonlinear self-action effects of intense ultra-short pulses in gaseous media under conditions of plasma generation.