Separation of High Order Harmonics with Fluoride Windows

Abstract

The lower orders produced in high order harmonic generation can be efficiently temporally separated into monochromatic pulses by propagation in a fluoride window while still preserving their femtosecond pulse duration. We present calculations for MgF 2 , CaF 2 , and LiF windows for the third, fifth, and seventh harmonics of 800 nm. We demonstrate the use of this simple and inexpensive technique in a femtosecond pump/probe experiment using the fifth harmonic.

VUV and XUV reflectance of optically coated mirrors for selection of high harmonics

“…By employing transmissive beam filters, such as gas, glass, and metal filters, further suppression of the undesired harmonics and selection of appropriate harmonic may be realized [10,20], in addition to blocking out the co-propagating driving field used to generate the harmonics [21]. Hence through the use of multilayer coated mirrors in parallel with other beam filtration methods, such as transmissive solid and gas filters, significant harmonic isolation can be achieved.…”

“…Since HHG produces a broad spectrum of discrete harmonics, and the ability to control this process to produce a relatively narrow spectrum, such as a single harmonic, is very limited in its current state, other methods for beam filtration have been explored. While techniques exist to disperse harmonics in time [10] and space [11], they generally result in significant losses and are limited in application to specific ranges of energies. An alternative approach is to use specialized optically coated mirrors that reflect the desired photons, while suppressing the undesired harmonics [12][13][14][15].…”