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.