Dramatic dwindling of the power spectrum of high order harmonics by shrinking of the gap size in bowtie nanostructures

• Published in: Journal of experimental and theoretical physics Vol. 124; no. 3; pp. 379 - 387
• Main Authors: Hosseinzadeh, F., Batebi, S., Soofi, M. Q.
• Format: Journal Article
• Language: English
• Published: Moscow Pleiades Publishing 01.03.2017; Springer; Springer Nature B.V
• Subjects: AMPLIFIERS; Atoms; Attosecond pulses; Classical and Quantum Gravitation; ELECTRONS; Elementary Particles; EMISSION; GOLD; HARMONIC GENERATION; HARMONICS; Helium; HELIUM IONS; ILLUMINANCE; Inhomogeneity; LASER RADIATION; Lasers; Molecules; NANOSCIENCE AND NANOTECHNOLOGY; NANOSTRUCTURES; Optics; Particle and Nuclear Physics; Physics; Physics and Astronomy; PULSES; Quantum Field Theory; Relativity Theory; Schrodinger equation; SCHROEDINGER EQUATION; Solid State Physics; SPECTRA; TIME DEPENDENCE; WAVE FUNCTIONS; WAVELENGTHS
• ISSN: 1063-7761; 1090-6509
• DOI: 10.1134/S1063776117020121

Our work is based on high harmonic generation in a gaseous medium (helium ion), by exploiting gold bowtie nanostructures as laser field amplifiers. As the result of emission of a laser pulse, the wave function of the atom varies with time; so, it is necessary to solve 1D time-dependent Schrödinger equation by means of split operator method. By illumination of a short duration, long wavelength three color laser pulse inside the gap, the enhanced field not only changes with time, but also varies in space. In this work we considered this space inhomogeneity in linear and nonlinear schemes. We show that in nonlinear case, the plateau region is more extended. We also show that in larger gaps, cutoff occurs on higher frequencies. But limitation of electron motion in bowtie nanostructures leads to the choice of an optimum 16 nm gap size in our case. We predict that, by the superposition of supercontinuum harmonics, a 26 attosecond pulse can be generated.