Abstract-Plasmonic Nanodisk Thin-Film Terahertz Photoconductive Antenna

 Nathan M. Burford, Michael J. Evans,  Magda O. El-Shenawee

http://ieeexplore.ieee.org/document/8239849/

This paper presents the design, fabrication, and measurement of a plasmonic thin-film terahertz photoconductive antenna. Conventional terahertz photoconductive antennas suffer from poor optical-to-terahertz conversion efficiency, often on the order of 10−4. This is due to the low quantum efficiency of the device. The goal of this work is to demonstrate enhanced terahertz emission from a plasmonic thin-film device architecture. The combination of plasmonic nanodisks, a 120-nm low-temperature-grown gallium arsenide thin-film, and a bottom-located bowtie antenna has demonstrated the feasibility of producing such devices. Fabrication attempts and failure analysis is discussed in this work. Experimental characterization measuring the peak-to-peak electric field values of the terahertz pulses emitted from the device prototypes showed approximately five times improvement in plasmonic thin-film devices compared to conventional devices. The plasmonic thin-film devices had a measureable terahertz bandwidth of ∼5 THz. This indicates that the plasmonic thin-film architecture has a potential for producing high optical-to-terahertz conversion efficiencies across a wide frequency range.

Abstract- Impact of Processing Conditions on Inter-tablet Coating Thickness Variations Measured by Terahertz In-Line Sensing

1. Hungyen Lin¹, 
2. Robert K. May^1,†, 
3. Michael J. Evans², 
4. Shuncong Zhong^3,‡, 
5. Lynn F. Gladden¹, 
6. Yaochun Shen³ and
7. J. Axel 

1. http://onlinelibrary.wiley.com/doi/10.1002/jps.24503/abstract

Article first published online: 2 JUN 2015

DOI: 10.1002/jps.24503

© 2015 Wiley Periodicals, Inc. and the American Pharmacists Association

A novel in-line technique utilising pulsed terahertz radiation for direct measurement of the film coating thickness of individual tablets during the coating process was previously developed and demonstrated on a production-scale coater. Here, we use this technique to monitor the evolution of tablet film coating thickness and its inter-tablet variability during the coating process under a number of different process conditions that have been purposefully induced in the production-scale coating process. The changes that were introduced to the coating process include removing the baffles from the coater, adding uncoated tablets to the running process, halting the drum, blockage of spray guns and changes to the spray rate. The terahertz sensor was able to pick up the resulting changes in average coating thickness in the coating drum and we report the impact of these process changes on the resulting coating quality. 

© 2015 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci