Open AccessNonlinear refraction and absorption measurements of thin films by the dual-arm Z-scan method
Author(s) -
Trenton R. Ensley,
Sepehr Benis,
Honghua Hu,
Zhong’an Li,
SeiHum Jang,
Alex K.Y. Jen,
Joseph W. Perry,
Joel M. Hales,
David J. Hagan,
Eric W. Van Stryland
Publication year - 2019
Publication title -
applied optics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.668
H-Index - 197
eISSN - 2155-3165
pISSN - 1559-128X
DOI - 10.1364/ao.58.000d28
Subject(s) - optics , substrate (aquarium) , materials science , thin film , signal (programming language) , z scan technique , refraction , phase (matter) , absorption (acoustics) , noise (video) , refractive index , nonlinear system , optoelectronics , nonlinear optics , physics , laser , computer science , nanotechnology , oceanography , quantum mechanics , artificial intelligence , geology , image (mathematics) , programming language
We extend the recently developed dual-arm Z-scan to increase the signal-to-noise ratio (SNR) for measuring the nonlinear refraction (NLR) of thin films on thick substrates. Similar to the case of solutes in solution, the phase shift due to NLR in a thin film can often be dominated by the phase shift due to NLR in the much thicker substrate. SNR enhancement is accomplished by simultaneously scanning a bare substrate and the film plus substrate in two separate but identical Z-scan arms. The subtraction of these signals taken simultaneously effectively cancels the nonlinear signal from the substrate, leaving only the signal from the film. More importantly, the SNR is increased since the correlated noise from effects such as beam-pointing instabilities cancels. To show the versatility of the dual-arm Z-scan method, we perform measurements on semiconductor and organic thin films, some less than 100 nm thick and with thicknesses up to 4 orders of magnitude less than the substrate.