Quantum-Path-Sensitive Extreme Ultraviolet Interferometry
High harmonic generation (HHG) is a method for producing attosecond duration pulses in the extreme ultraviolet and soft x-ray spectral regions. In this process an intense laser pulse ionizes a low-density gas, with the subsequent laser-driven electron dynamics resulting in the emission of photons at high-order harmonics of the fundamental laser frequency. The high temporal and spatial coherence achievable with HHG make it an attractive source for a host of applications including the real time observation of ultrafast dynamics in gases and solids [1], as well as the high resolution microscopy of nanostructures [2].
It is well known that for all but the highest harmonic photon energies there are two different quantum paths which contribute to a particular harmonic order, referred to as the “long” and “short” quantum trajectories. Since the phase of harmonics depends sensitively both on the quantum path, as well as the intensity of the driving laser pulse, precise characterization of the phase contribution to the harmonic field arising from quantum paths is key to fully exploiting the properties of these sources.
In this talk a new technique for characterizing HHG quantum paths is described. An inline XUV interferometer consisting of two longitudinally separated high harmonic generation regions is used to unambiguously observe interference between the long and short quantum trajectories. Recent experiments to control and measure [3] the spatial structure of HHG for high-resolution microscopy are also presented.
[1] J. C. Petersen et al. Phys. Rev. Lett. 107, 177402, (2011)
[2] M. Odstrcil et al. Optics Express. 24, 8360, (2016)
[3] D. Lloyd et al. Scientific Reports, 6, 30504, (2016)
Dr. Kevin O'Keeffe
Swansea University
Singleton Park, Sketty
Swansea SA2 8PP
UK
| Phone | +44 1792 602246 |
| Dr. Kevin O'Keffe | |
| Http | Dr. Kevin O'Keeffe |
| Swansea University |