Del Mar Photonics

Femtosecond pulse shaping references

R. Bartels, M.M. Murnane, H.C. Kapteyn, I. Christov, H. Rabitz
Learning from Learning Algorithms: Applications to attosecond dynamics of high-harmonic generation.
PHYSICAL REVIEW A 70(1):1-5 (October 2004).

Using experiment and modeling, we show that the data set generated
when a learning algorithm is used to optimize a quantum system can
help to uncover the physics behind the process being optimized. In
particular, by optimizing the process of high-harmonic generation
using shaped light pulses, we generate a large data set and analyze
its statistical behavior. This behavior is then compared with
theoretical predictions, verifying our understanding of the
attosecond dynamics of high harmonic generation and uncovering an
anomalous region of parameter space.

R. Bartels, S. Backus, E. Zeek, L. Misoguti, G. Vdovin, I. Christov, M.M. Murnane, H.C. Kapteyn
Shaped-pulse optimization of coherent soft-x-rays. NATURE 406,
164-166 (2000).

High-harmonic generation is one of the most extreme nonlinear-optical
processes observed to date. By focusing an intense laser pulse
into a gas, the light-atom interaction that occurs during the process
of ionising the atoms results in the generation of harmonics of the
driving laser frequency, that extend up to order ~300 (corresponding
to photon energies from 4 to >500eV). Because this technique is
simple to implement and generates coherent, laser-like, soft-x-ray
beams, it is currently being developed for applications in science
and technology including probing of dynamics in chemical and
materials systems and for imaging. In this work we demonstrate
that by carefully controlling the shape of intense light pulses of
6-8 optical cycles, we can control the interaction of light
with an atom as it is being ionised, in a way that improves the
efficiency of x-ray generation by an order of magnitude. Furthermore,
we demonstrate that it is possible to control the spectral
characteristics of the emitted radiation and to "channel" the
interaction between different-order nonlinear processes. The result
is an increased utility of harmonic generation as a light source, as
well as the first demonstration of optical pulse-shaping techniques
to control high-order nonlinear processes.