title: Application of Photoreactive Barium Titanate (BaTiO₃) Beam Fanning to the Photothermal Mirror Technique: An Experimental Analysis.
abstract: An adaptive spatial filter is used as an optical novelty filter to detect photothermal mirror (PM) signals in high absorbing materials using continuous wave laser excitation. The optical novelty filter uses an optical beam-fanning limiter based on single domain barium titanate (BaTiO3), cut and poled 45° relative to the c-axis. The optical novelty filter approach relaxes the requirement for high sample surface smoothness because the effect aperture adapts to the surface, reducing the stationary background from the optical signal and provides a means of developing the photothermal mirror signal. Time-dependent probe laser phase shifts due to photothermal surface deformation pass through the optical novelty filter and are detected as an intensity increase over the stationary or "mundane" signal. Experimental studies are performed using four well-characterized metals using both the conventional photothermal mirror and optical novelty filter apparatuses in order to understand the complicated signal behavior. Signal behavior is analyzed in different excitation intervals using pseudo-chopped sample excitation with different duty cycles. Optical novelty filter signals show fast response for changes in the spatial beam profile followed by long relaxation time. Reasons for the optical novelty filter response are described.
authors.affiliation: Department of Chemistry and Biochemistry, Utah State University, Logan, UT 84322 USA.
authors.forename: Vitor Santaella
authors.initials: VS
authors.lastname: Zanuto
authors.forename: Otávio Augusto
authors.initials: OA
authors.lastname: Capeloto
authors.forename: Gustavo Vinicius Bassi
authors.initials: GV
authors.lastname: Lukasievicz
authors.forename: Leandro Silva
authors.initials: LS
authors.lastname: Herculano
authors.forename: Luis Carlos
authors.initials: LC
authors.lastname: Malacarne
authors.forename: Nelson Guilherme Castelli
authors.initials: NG
authors.lastname: Astrath
authors.forename: Stephen Edward
authors.initials: SE
authors.lastname: Bialkowski