Louis DiMauro

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Louis DiMauro OSU 2005
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Louis DiMauro OSU 2005
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electron energy Ee h? - ip

• transition probability P ?F?where ? ? cm2, F
  ? ?/cm2 s, ? ? s
• consider cw-light? (1A)2 10-16 cm2for P ?
  1 F 1016 ? /cm2 sor intensity I 10-3 W/cm2
• 100 fs (10-13 s) light pulsefor P ? 1 F 1029
  ? /cm2 sor intensity I 1010 W/cm2

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2-photon case (h? ? ip)
transition probability P ?a F ? ?b F ? or P
?2 F2 ? where ?2 ? ?a ? ?b cm4 s
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Tunnel Rate ? 1/E eE
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• electrons are emitted as burst every ½-cycle.

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Xe Ip 12.1 eV Ee Nh? - Ip 0.53 ?m, N6,
EN1.9 eV 1.06 ?m, N11, EN0.77 eV ATI ?NS
(NS)h? - Ip 0.53 ?m, S1, E74.2 eV
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• ponderomotive or quiver energy Up ? l2 ? /4
• displacement a ? l2 E

• For 800 nm (red) laser at 1015 W/cm2 Up 60
  eV a 50 au (25 A)

think in ponderomotive units !!!
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• xenon
• long pulse, 30 ps
• 1 ?m , 30 TW/cm2

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• electrons are repelled from regions of high
  intensity.
• long pulse (adiabatic)quiver E ? translational

?NS(r,?) (NS)h? - Ip Up(r,?)
Up(r,?) intensity-independent energy
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Freeman et al. PRL 59, 1092 (1987)
for short pulse the ponderomotive gradient is
negligible.
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I ?
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• quasi-classical description
• Gallagher, PRL 61, 2304 (1988)
• Van Linden van den Heuvell Muller, in
  Multiphoton Processes (1988)
• Corkum, Burnett Brunel, PRL 62, 1259 (1989)

electric fieldE Eo sin?t
velocityv(t) Eo/?cos?t - cos?o vo
quiver drift for tunneling, vo0
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v(t) Eo/?cos?t - cos?o Quiver Drift
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remember Up ? ? !!!
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helium, 0.8 ?m, 1 PW/cm2
ideal case 10 Hz 100 channel experiment 100
e/shot or 1 e/chs, 105 range ? 28 hrs!
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• n-photon ionization perturbation theory P ?n
  Fn ?
• saturation (depletion) P ? ? ? Fs (?n ?)-1/n
• helium (24 eV, 16-photons)
• Fs 1033 p/scm2 or Es 0.1 au

• over-the-barrier ionization
• V(x) -Ze2/x eEox
• solve for Eo
• Eo Ip2/4q3Z
• helium Eo 0.2 au

answer 1 au field is adequate for neutral atomic
ionization!
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baseline 1 au field strength (3.5 ? 1016
W/cm2) pulse 100 fs duration 4 ?m beam
waist ? 1 mJ pulse energy typical laser
produces a few Watts average power ? 103 pulses
per second

• kilohertz regenerative amplification (late
  1980s)
• Mourou, Bado, Bouvier (Rochester)
• Saeed, Kim, DiMauro (BNL)
• Fayer (Stanford)
• seminal work (LLNL)
• Lowdermilk Murray, J App. Phys. 51, 2436
  (1980).

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• cw or quasi-cw pumping
• factors absorption spectrum, lifetime, thermal
  coefficients,
• material properties
• damage, saturation fluence,
• YLF, YAG, glass millisecond lifetimes, broad
  absorption
• poor thermal properties, narrow emission ??
• Tisapphire microsecond lifetimes, narrow
  absorption
• good thermal properties, broad emission ??

• advantages of regenerative amplification
• high amplification 106-8
• excellent spatial mode
• good stability 1-3 rms

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• extract maximum energy
• minimize optical damage

• state-of-the-art systems ? 1020 W/cm2
• kilohertz operation ? 1016 W/cm2

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xenon, 1 ?m, 1013 W/cm2

• higher sensitivity ? new insights

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tomorrows plat du jour helium the rebirth of
the classical picture