54th Annual Meeting of the APS Division of Plasma Physics
Volume 57, Number 12
Monday–Friday, October 29–November 2 2012;
Providence, Rhode Island
Session CI2: Beams and Coherent Radiation
2:00 PM–5:00 PM,
Monday, October 29, 2012
Room: Ballroom DE
Chair: Eric Esarey, Lawrence Berkeley National Laboratory
Abstract ID: BAPS.2012.DPP.CI2.2
Abstract: CI2.00002 : Modeling of ultrafast laser induced electron emission from a sharp tip*
2:30 PM–3:00 PM
Preview Abstract
Abstract
Author:
Lay Kee (Ricky) Ang
(Singapore University of Technology and Design)
The emission mechanism of ultrafast laser induced electron emission from a
sharp metallic tip has attracted considerable interest in recent years due
to its applications, such as ultrafast electron-beam based imaging at
nanometer scale, and also as high brightness short electron bunches for
applications in future light sources such as x-ray free-electron lasers. The
underlying electron emission mechanism is difficult to pin down as it occurs
in the region of Keldysh parameter $\gamma \sim $ 1, which is between the
multiphoton ($\gamma >>$ 1) and tunneling $\gamma <<$ 1) regimes.
In this paper, we will present a consistent time-dependent quantum model
that is able to combine the effects of (a) time-dependent tunneling, (2)
ultrafast laser non-equilibrium excitation on metal, and (3) field gradient
on the tip. It is found that the onset of the tunneling regime is given by a
universal formula, depends only on the work function over a wide range of
laser parameters. More interestingly, the classical concept of photoelectric
effect for electron emission by absorption $N$ number of photons is no longer
valid at very short time scale for which the required $N$ may be reduced by a
photon by using a sub-10 fs ultrafast laser. The non-equilibrium electron
distribution due to ultrafast laser excitation is also self-consistently
included with good agreement with experimental findings. Due to the close
correlation between the amount of electron emission and the phase of the
ultrafast laser pulse, this model may provide a new way measure the phase of
the laser. While the model is initially focused on metallic tip, it is ready
to extend to novel materials such as single-layer graphene, for which a
relativistic quantum model has been created to include the effect of Klein
tunneling. These results show that traditional equilibrium models in the
electron emission process will require a revision in the limit of ultrafast
time scale, when the laser pulse length is comparable or shorter to the
tunneling time, and also to the electron relaxation time. Dependence of
laser parameters (wavelength, pulse length, phase) and material properties
will be studied thoroughly.
*It is funded by SUTD-MIT IDC [SRG EPD 2011 014, IDSF200102, IDG21200106 21200103]
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2012.DPP.CI2.2