Efficient material parameters estimation with terahertz time-domain spectroscopy

Osman S. Ahmed; Mohamed A. Swillam; Mohamed H. Bakr; Xun Li

doi:10.1117/12.873336

23 February 2011 Efficient material parameters estimation with terahertz time-domain spectroscopy

Osman S. Ahmed, Mohamed A. Swillam, Mohamed H. Bakr, Xun Li

Proceedings Volume 7938, Terahertz Technology and Applications IV; 793805 (2011) https://doi.org/10.1117/12.873336
Event: SPIE OPTO, 2011, San Francisco, California, United States

Abstract

Existing parameter extraction techniques in the terahertz range utilize the magnitude and phase of the transmission function at different frequencies. The number of unknowns is larger than the number of available information creating a nonuniqueness problem. The estimation of the material thickness thus suffers from inaccuracies. We propose a novel optimization technique for the estimation of material refractive index in the terahertz frequency range. The algorithm is applied for materials with arbitrary frequency dependence. Dispersive dielectric models are embedded for accurate parameter extraction of a sample with unknown thickness. Instead of solving N expensive nonlinear optimization problems with different possible material thickness, our technique obtains the optimal material thickness by solving only one optimization problem. The solution of the utilized optimization problem is accelerated by estimating both the first order derivatives (gradient) and second order derivatives (Hessian) of the objective function and supplying them to the optimizer. Our approach has been successfully illustrated through a number of examples with different dispersive models. The examples include the characterization of carbon nanotubes. The technique has also been successfully applied to materials characterized by the Cole-Cole, Debye, and Lorentz models.

Citation Download Citation

Osman S. Ahmed, Mohamed A. Swillam, Mohamed H. Bakr, and Xun Li "Efficient material parameters estimation with terahertz time-domain spectroscopy", Proc. SPIE 7938, Terahertz Technology and Applications IV, 793805 (23 February 2011); https://doi.org/10.1117/12.873336

ACCESS THE FULL ARTICLE

INSTITUTIONAL
Select your institution to access the SPIE Digital Library.

SELECT YOUR INSTITUTION

PERSONAL
Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.

PERSONAL SIGN IN

No SPIE Account? Create one

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available