title: A Dual-Colour Architecture for Pump-Probe Spectroscopy of Ultrafast Magnetization Dynamics in the Sub-10-femtosecond Range.
abstract: Current time-resolution-limited dynamic measurements clearly show the need for improved techniques to access processes on the sub-10-femtosecond timescale. To access this regime, we have designed and constructed a state-of-the-art time-resolved magneto-optic Kerr effect apparatus, based on a new dual-color scheme, for the measurement of ultrafast demagnetization and precessional dynamics in magnetic materials. This system can operate well below the current temporal ranges reported in the literature, which typically lie in the region of around 50 fs and above. We have used a dual-colour scheme, based on ultra broadband hollow-core fibre and chirped mirror pulse compression techniques, to obtain unprecedented sub-8-fs pump and probe pulse durations at the sample plane. To demonstrate the capabilities of this system for ultrafast demagnetization and precessional dynamics studies, we have performed measurements in a ferrimagnetic GdFeCo thin film. Our study has shown that the magnetization shows a sudden drop within the first picosecond after the pump pulse, a fast recovery (remagnetization) within a few picoseconds, followed by a clear oscillation or precession during a slower magnetization recovery. Moreover, we have experimentally confirmed for the first time that a sub-10-fs pulse is able to efficiently excite a magnetic system such as GdFeCo.
authors.affiliation: Departamento de Física e Astronomia and IFIMUP-IN, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre 687, 4169-007 Porto, Portugal.
authors.forename: C S
authors.initials: CS
authors.lastname: Gonçalves
authors.affiliation: Departamento de Física e Astronomia and IFIMUP-IN, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre 687, 4169-007 Porto, Portugal.
authors.forename: A S
authors.initials: AS
authors.lastname: Silva
authors.affiliation: Departamento de Física e Astronomia and IFIMUP-IN, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre 687, 4169-007 Porto, Portugal.
authors.forename: D
authors.initials: D
authors.lastname: Navas
authors.affiliation: Department of Physics, Lund University, P.O. Box 118, SE-221 00 Lund, Sweden.
authors.forename: M
authors.initials: M
authors.lastname: Miranda
authors.affiliation: Departamento de Física e Astronomia and IFIMUP-IN, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre 687, 4169-007 Porto, Portugal.
authors.forename: F
authors.initials: F
authors.lastname: Silva
authors.affiliation: Departamento de Física e Astronomia and IFIMUP-IN, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre 687, 4169-007 Porto, Portugal.
authors.forename: H
authors.initials: H
authors.lastname: Crespo
authors.affiliation: Departamento de Física e Astronomia and IFIMUP-IN, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre 687, 4169-007 Porto, Portugal.|Laboratoire PROMES CNRS (UPR 8521), Université de Perpignan Via Domitia, Perpignan, France.
authors.forename: D S
authors.initials: DS
authors.lastname: Schmool