Novel Driving Lasers for the Next Generation Attosecond Sources
Abstract
The aim of this project is to advance the technology behind attosecond pulse duration in two ways: though increased power in a synthesized optical pulse (resulting from the coherent overlap of multiple broadband pulses in neighboring spectral regions) and the expansion of the concept to the short-wave infrared (SWIR) and near infrared (NIR) spectral regions, combined with exact knowledge of the temporal structure of the electric field. The resulting light source is expected to provide single-cycle infrared pulses containing hundreds of microjoules of energy. Attosecond pulses are generated when an atom is ionized by a light wave, and subsequently the liberated electron is accelerated away from, and then back towards the ion. If the electron returns to the parent ion and recombines, the excess energy is released as a high-energy photon. As this recollision can only happen at a specific time within the oscillation cycle of the laser, the process releases a coherent, and extremely short, burst of extreme ultraviolet or soft x-ray radiation: an attosecond pulse. These pulses have been used to explore electronic motion on the fastest accessible time-scales, and are still revealing new insight into the fundamental physics of light-matter interaction. The process has its limitations, however: the conversion efficiency is low, and the photon energy is limited by ionization rate, phase-matching and intensity. Thus, most experiments using Ti:Sapphire-based lasers operating at 800 nm central wavelength have taken place in the range of photon energies below 150 eV. The photon energy at a given intensity scales with the square of the wavelength of the laser however, making it conceivable to reach higher energies using infrared driving sources. In this project, the source to be generated will have a central wavelength of approximately 1.5 µm (200 THz). By spectral broadening of a 2-µm pulse with > 1 mJ of energy and < 20 fs pulse duration (produced by an optical parametric amplifier) in a hollow core fiber filled with argon gas, a high-power supercontinuum spanning 300 nm to 3 µm is produced. A set of custom multilayer optics will produce three compressed optical channels, one from 1.4 to 2.7 µm (SWIR), one from 0.7 µm to 1.3 µm (NIR), and one from 0.3 µm to 0.6 µm (EOS). The two infrared channels, SWIR and NIR will be coherently combined to produce an extremely short pulse, consisting of only one electromagnetic oscillation. The UV-visible channel, EOS, will be used for electro-optically sample the IR pulse, providing complete temporal characterization of the infrared field. The ability to perform high-harmonic generation with a precisely-known and single-cycle field will make it possible to test, among many other aspects of light-matter interaction, models of the generation of attosecond pulses with unprecedented precision and allow fine optimization of the process, advancing the production and application of attosecond pulses to the next generation of experiments.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jan 12, 2017
- Source ID
- W911NF1510360
Entities
People
- Ferenc Krausz
Organizations
- Army Contracting Command
- Max Planck Society
- United States Army