Open AccessApplication of wavelet analysis on transient reflectivity in ultra-thin films
Author(s) -
Saeed Yousefi Sarraf,
Robbyn Trappen,
Shalini Kumari,
Ghadendra Bhandari,
Navid Mottaghi,
ChennJung Huang,
Gonzalo Cabrera,
Alan D. Bristow,
Mikel B. Holcomb
Publication year - 2019
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.27.014684
Subject(s) - wavelet , optics , signal (programming language) , materials science , residual , transient (computer programming) , thin film , energy (signal processing) , heterojunction , fourier transform , physics , optoelectronics , computer science , nanotechnology , algorithm , artificial intelligence , quantum mechanics , programming language , operating system
Applications of wavelet analysis in ultra-thin film transient reflectivity (TR) measurements have been investigated. Advantages of utilizing different localized wavelet bases, in position and time, have been addressed on the residual TR signals. Morse wavelets have been used to obtain information from the abrupt oscillatory modes in the signal, which are not distinguishable with conventional methods such as Fourier transforms. These abrupt oscillatory modes are caused by the surface, interface, or any short-lived oscillatory modes which are suppressed in the TR signal in ultra-thin films. It is demonstrated that by choosing different Morse wavelets, information regarding different oscillatory modes in the TR signal of a heterostructure thin film is achievable. Moreover, by performing wavelet analysis on multiferroic heterostructures, oscillatory modes with very close energy ranges are easily distinguishable. For illustration, residuals of the TR signals have been obtained by a pump-probe setup in reflectivity mode on La 0.7 Sr 0.3 MnO 3 /SrTiO 3 and BaTiO 3 /La 0.7 Sr 0.3 MnO 3 /SrTiO 3 samples, where sufficient signal to noise ratios have been achieved by taking multiple scans. The residual signals have been analyzed with Morse wavelets, and multiple oscillatory modes with close energy ranges have been observed and distinguished. This approach can isolate the location of various oscillatory modes at the surface, interface and in the bulk of the heterostructure sample.