Terahertz (T-rays) spectroscopy has recently emerged as a powerful method to access a heretofore barely explored region of the electromagnetic spectrum where fundamental molecular resonances occur. Besides their importance for fundamental research, these resonances could be used as signatures in the identification of molecular species and as sensitive probes in a wide variety of molecular processes.
In this paper we consider the potential of THz spectroscopy in the application to relevant biomedical and homeland security problems such as the analysis of normal and diseased tissues and the detection of toxic biomolecules.
As examples, we present preliminary experimental data which suggest that THz spectroscopy: 1) can discriminate between cancerous and normal tissue, and 2) can reveal the presence of foreign substances hidden in an envelope and even allow their specific identification. This capability is of particular relevance as a straightforward homeland security tool for the detection of anthrax and other biotoxic molecules.
Short infrared pulses have been generated by nonlinear mixing of the wavelengths from a two color femtosecond modelocked Ti:Sapphire laser. The pulses can be tuned from 7 to 12 micrometers and are used to perform a direct measurement of the speed of a GaAs/Al0.2Ga0.8As quantum well infrared photodetector. The electrical response of the detector has rise and decay times of less than 95 ps and the FWHM is 115 ps.
Transient photoluminescence, photoluminescence excitation and picosecond photoinduced absorption studies on stretch oriented phenylenevinylene polymer films are presented. A coherent picture of the processes occurring after light absorption emerges which can account for the data. The implications of this picture for photoconductivity and electroluminescence are considered.
We use nanosecond and picosecond optical spectroscopic techniques
to isolate and study the photodynamics of the single particle spectrum of
35A CdSe nanoclusters exhibiting three-dimensional quantum confinement.