IREE Supplement for the Engineering Research Center on Mid-InfraRed Technologies for Health and the Environment Afusat Dirisu 1 , Dmitry Revin 2 , Zhijun Liu 3 , John Cockburn 4 , Claire Gmachl 5 1,3,5 Center for Mid-Infrared Technologies for Health and the Environment, Princeton University, Princeton, NJ 08544, USA. Email: adirisu@princeton.edu . 2,4 Department of Physics and Astronomy, University of Sheffield, Sheffield, UK S3 7RH ABSTRACT: The IREE supplement award granted to the MIRTHE center provided a five month long research experience in the Mid-IR group of the Physics department at University of Sheffield, UK (host laboratory). Two research projects were planned. The first was the design and growth of short wavelength (3-5m) Quantum Cascade Lasers (QCL). This project was not completed due to equipment problems throughout the five months stay but literature research of the benefits and limitations of the material systems used for short wavelength QCL was performed. The second project was to use an existing technique, pioneered in the host laboratory, for probing the intersubband electron distribution of QCL as temperature and bias conditions are modified. By understanding the distribution of the electrons under various operating conditions one can have a good understanding of the performance of the QCL. At least one journal publication is expected from the analysis of the results obtained. The international travel provided the award recipient diverse cultural experiences and extensive interaction with both the scientific and non- scientific communities in different parts of Europe. This could otherwise not have been possible. INTRODUCTION The awardee institution for the IREE NSF award is the center for Mid-Infrared Technologies for Health and the Environment (MIRTHE) in Princeton, NJ, USA. MIRTHE research is focused on developing state of the art Mid-IR sensors for environmental and health monitoring. One of the major components of these sensors is