pre-excitation of rb atoms by frequency chirped laser pulses for efficient plasma generation
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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 generationG.P. DjotyanWigner Centre for Physics of the Hungarian Academy of Sciences
Contributors: D. Dzsotjan Zs. Srlei J. Bakos G. Demeter N. Sandor
OutlineFrequency 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
Over-barrier and impact ionization of excited Rb atoms
Action of a laser pulse with area A = (t) dt = 5
Action of a frequency-chirped laser pulse on a two-level atom
Coherent Population Transfer to a Target State Without Excitation of the Atom: Interaction of a single frequency chirped laser pulse with L atom
Dynamics of the populations of the L-atom in the field of single narrowband frequency-chirped laser pulse
n2
n3
n1
-3-2-10123TIME00.20.40.60.81SNOITALUPOPn1n3n2G.P. Djotyan, J.S. Bakos, Zs. Srlei, J.Szigeti, Phys.Rev.A, 70, 063406 (2004) Creation of superposition between a ground and excited state
G.P. Djotyan, N. Sandor, J.S. Bakos, Zs. Srlei, Opt. Express, 19, n. 18, 17493(2011)
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)
Using frequency-chirped pulses in manipulation of translational states of atoms
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) 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)
Parameters of the MOT and of the trapped and cooled atomic cloud Volume ~ 1 mm3Number of atoms ~ 10 7Lifetime ~ 500 msecTemperature ~ 10 -100 K
Rb transition lines and the ionization scheme
Dynamics of the populations for positive and negative frequency chirp
I0>I1>I2>I3>I4>I5>
Final populations of the ground state 5s and first excited state
5s 5pFinal populations of the excited states 5d and 7s
5d 7sConclusionsFrequency 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.
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.