US Patent-Thickness determination and layer characterization using terahertz scanning reflectometry

United States Patent 9909986
Inventors:
Rahman, Anis (Hummelstown, PA, US) 
Rahman, Aunik K. (Hummelstown, PA, US) 

http://www.freepatentsonline.com/9909986.html


A terahertz scanning reflectometer system is described herein for in-situ measurement of polymer coating thickness, semiconductor wafer's surface sub-surface inspection in a non-destructive and non-invasive fashion with very high resolution (e.g., 25 nm or lower) and spectral profiling and imaging of surface and sub-surface of biological tissues (e.g., skin) in a non-invasive fashion

Abstract-Terahertz 3D Imaging of Nanomaterial Interfaces for Sub-nanometer Analysis

Anis Rahman and Aunik Rahman

https://www.osapublishing.org/abstract.cfm?uri=CLEO_AT-2016-ATu4J.7

Sub-nanometer imaging with size measurement was achieved via terahertz route. We describe a new technique of 3D imaging with layer-by-layer inspection capability in a non-contact fashion with resolution less than a nanometer. A high power, CW terahertz energy is utilized for scanning a specimen.

© 2016 OSA

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Abstract-Dendrimer Dipole Excitation: A New Mechanism for Terahertz Generation

Anis Rahman A1*, Aunik Rahman1 and Donald A Tomalia2

1Applied Research and Photonics, 470 Friendship Road, Suite 10, Harrisburg, PA 17111, USA

2Nano Synthons LLC, 1200 N, Fancher Avenue, Mt. Pleasant, MI 48858, USA http://www.omicsonline.org/open-access/dendrimer-dipole-excitation-a-new-mechanism-for-terahertz-generation-2155-6210-1000196.php?aid=68714

An electro-optic dendrimer (EO dendrimer) material has been designed for high power terahertz generation. An ordinary poly (amidoamine organosilicon) (PAMAMOS) dendrimer was modified via doping and poling to generate a high electro-optic coefficient nanomaterial. Measured EO coefficient varied from ~130 pm/V at 633 nm to ~90 pm/V at 1553 nm. An emitter designed from this EO dendrimer generates milliwatts of continuous wave (CW) terahertz radiation (T-ray) when pumped by a CW laser of suitable wavelength. The mechanism termed as the dendrimer dipole excitation (DDE) works via excitation of the dipole population generated by the doping process. The doping protocol also generates a distribution of dipole moments, as opposed to fixed dipoles in the lattice of a crystalline material; thus, when excited by a suitable pump laser, these dipoles radiate a broadband frequency that range from 0.1 THz to ~ 30 THz. A terahertz time-domain spectrometer (TeraSpectra) was designed with this DDE terahertz source. As a test of the spectrometer functionality, a standard polyethylene calibration was conducted. It was found that TeraSpectra reproduces several known absorbance peaks of polyethylene. It also produces additional absorbance peaks not observed before. It is surmised that the ultra-high sensitivity of T-ray enables observation and discovery of additional absorbance peaks that are not visible via other spectroscopy such as visible, UV, FTIR or Raman.

Abstract-Terahertz scanning reflectometer

United States Patent 9239290

Inventors:

Rahman, Anis (Hummelstown, PA, US) 

Rahman, Aunik K. (Hummelstown, PA, US
http://www.freepatentsonline.com/9239290.html

A terahertz scanning reflectometer is described herein. A high sensitivity terahertz scanning reflectometer is used to measure dynamic surface deformation and delamination characteristics in real-time. A number of crucial parameters can be extracted from the reflectance measurements such as dynamic deformation, propagation velocity, and final relaxation position. A terahertz reflectometer and spectrometer are used to determine the permeation kinetics and concentration profile of active ingredients in stratum corneum.