{"id":190370,"date":"2025-10-10T11:52:07","date_gmt":"2025-10-10T11:52:07","guid":{"rendered":"https:\/\/www.newsbeep.com\/uk\/190370\/"},"modified":"2025-10-10T11:52:07","modified_gmt":"2025-10-10T11:52:07","slug":"ultrafast-laser-pulses-reveal-solid-state-bandgaps-in-motion","status":"publish","type":"post","link":"https:\/\/www.newsbeep.com\/uk\/190370\/","title":{"rendered":"Ultrafast laser pulses reveal solid-state bandgaps in motion"},"content":{"rendered":"

\"Watching<\/p>\n

Schematic of extreme-ultraviolet high-harmonic interferometry of solids.Two phase-locked near-infrared pulses generate high-order harmonics in a solid sample. Interference of the emitted XUV fields encodes transient changes in the electronic bandgap, revealing how strong-field excitation modifies the material’s electronic structure on femtosecond timescales. Credit: MBI \/ Dr. Peter J\u00fcrgens-Goltermann<\/p>\n

The bandgap, i.e. the energy gap between the highest lying valence and the lowest lying conduction band, is a defining property of insulating solids, governing how they absorb light and conduct electricity. Tracking how a bandgap changes under strong laser excitation has been a long-standing challenge, since the underlying processes unfold on femtosecond timescales and are difficult to track directly, especially for wide-bandgap dielectrics.<\/p>\n

In a collaboration<\/a> between the Max-Born-Institute, ARCNL Amsterdam, and Aarhus University, researchers have now shown that extreme ultraviolet (XUV) high-harmonic interferometry can provide direct access to such dynamics.<\/p>\n

Using pairs of phase-locked near-infrared laser pulses, the team measured interference fringes<\/a> and their intensity-dependent shift in the generated high-order harmonics from silica glass (SiO2) and magnesium oxide (MgO).<\/p>\n

These fringe shifts encode transient changes of the electronic bandgap, with silica showing signatures of a shrinking bandgap<\/a>, while MgO exhibits a widening.<\/p>\n

The experiments were supported by analytical modeling and semiconductor Bloch-equation simulations, confirming that the observed phase variations are consistent with excitation-induced modifications of the electronic structure.<\/p>\n

The work establishes interferometric HHG as a broadly applicable, all-optical probe of band-structure dynamics in solids. Beyond fundamental insight, this approach opens pathways toward ultrafast semiconductor metrology and future petahertz electro-optic technologies.<\/p>\n

\"Watching<\/p>\n

Experimental setup for generating phase-locked NIR and XUV pulse pairs using a common-path interferometer. Credit: MBI \/ Dr. Peter J\u00fcrgens-Goltermann<\/p>\n

\"Watching<\/p>\n

(a) and (b) Intensity-dependent high-harmonic phase shifts in SiO2(a) and MgO (b). (c) Extracted bandgap variation in SiO2. (d) Same as (c) but for MgO. Credit: MBI \/ Dr. Peter J\u00fcrgens-Goltermann<\/p>\n

More information:
\n\t\t\t\t\t\t\t\t\t\t\t\tLisa-Marie Koll et al, Extreme ultraviolet high-harmonic interferometry of excitation-induced bandgap dynamics in solids, Optica (2025). DOI: 10.1364\/optica.559022<\/a><\/p>\n

\n\t\t\t\t\t\t\t\t\t\t\t\t\tProvided by
\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\tMax Born Institute for Nonlinear Optics and Short Pulse Spectroscopy<\/a>
\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/p>\n

\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/a>\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/p>\n

\n\t\t\t\t\t\t\t\t\t\t\t\tCitation:
\n\t\t\t\t\t\t\t\t\t\t\t\tUltrafast laser pulses reveal solid-state bandgaps in motion (2025, October 9)
\n\t\t\t\t\t\t\t\t\t\t\t\tretrieved 10 October 2025
\n\t\t\t\t\t\t\t\t\t\t\t\tfrom https:\/\/phys.org\/news\/2025-10-ultrafast-laser-pulses-reveal-solid.html\n\t\t\t\t\t\t\t\t\t\t\t <\/p>\n

\n\t\t\t\t\t\t\t\t\t\t\t This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no
\n\t\t\t\t\t\t\t\t\t\t\t part may be reproduced without the written permission. The content is provided for information purposes only.\n\t\t\t\t\t\t\t\t\t\t\t <\/p>\n","protected":false},"excerpt":{"rendered":"Schematic of extreme-ultraviolet high-harmonic interferometry of solids.Two phase-locked near-infrared pulses generate high-order harmonics in a solid sample. Interference…\n","protected":false},"author":2,"featured_media":190371,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[24],"tags":[2303,2304,2302,2299,90,2300,86,2301,56,54,55],"class_list":["post-190370","post","type-post","status-publish","format-standard","has-post-thumbnail","category-physics","tag-materials","tag-nanotech","tag-physics","tag-physics-news","tag-science","tag-science-news","tag-technology","tag-technology-news","tag-uk","tag-united-kingdom","tag-unitedkingdom"],"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/posts\/190370","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/comments?post=190370"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/posts\/190370\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/media\/190371"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/media?parent=190370"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/categories?post=190370"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/tags?post=190370"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}