Attosecond Electron Synchrotron on a Nanoscale

Princeton University, Princeton NJ

Investigators

Abstract

Intense laser light may bring some of the science and applications of large particle accelerators down to a moderate-size laboratory, making it accessible to a broader range of researchers and users in multiple fields of science and technology. From the radiation physics perspective, an advantage of lasers is their ability to generate unprecedentedly short (attosecond) pulses of ultraviolet and x-ray radiation. Even though the spatial scales are drastically different, the physics of emission by electrons in large-scale synchrotron facilities (major research tools for x-ray crystallography and materials science research) and by electrons undergoing acceleration at the surface of a solid under the influence of extreme-intensity light fields are, in an essential way, the same. The interaction of intense, ultrashort-pulsed light with solids results in target ionization and the momentary formation of something akin to a nanometer-sized "synchrotron" (the charged particles emit bursts of high-energy radiation within time intervals much shorter than the half-cycle of the driving light field). This process can be controlled by the details of how the incident light field waveforms evolve with time. Taming synchrotron-type electron trajectories in solids by specially prepared laser fields, and ensuring that the result is the emission of intense ultraviolet and x-ray radiation is the aim of this program. This program will explore the chance to enhance the intensity of coherent ultraviolet and x-ray emission from solids under extreme light fields by sub-cycle shaping of the driving laser pulse waveforms. The waveform shaping can be achieved through mixing the laser fundamental frequency with its second harmonic or higher frequency components. The effect of the energy distribution of different colors in the driving field as well as the phase delay between them on the radiation spectra will be studied. The program will seek the optimized solutions for driving waveforms, as well as the physical limits on the efficiency of the process. This study may provide new insight into the dynamics of field-controlled electron oscillations in laser-produced solid-density plasmas. Ultimately, this approach may offer higher attosecond pulse intensities than those currently achieved, opening a pathway to advance ultrafast metrology toward time-resolved x-ray pump-probe spectroscopy.