HIGH RESOLUTION SPECTROSCOPY BY PICOSECOND PULSE DEMODULATION.

Author Institution: Ohio State University, 174 West 18th Avenue, Columbus, OH 43210-1106.; North Carolina Central University, Durham NC 27707.; Duke University, Durham, NC 27706.; Massachusetts Institute of Technology, Lexington, MA 02173-9108.; U.S. Army Research Office, Research Triangle Park, NC 27709.Sources with terahertz bandwidth spectral content can be obtained by demodulationg picosecond pulses. Examples of such source include those based on the coupling between relativistic elecron bunches and periodic structure in an orotron device and semiconductor switches driven by femtosecond laser pulses. For those periodically pulsed sources, the spectragenerated are also periodic with narrow spectral lines spaced at the inverse repetition rate. For cw sources, the individual spectral line width is usually only a few kilohertz. For pulsed sources, the spectral width can be transform limited. By using optical signal processing methods, we have produced a high resolution spectroscopic system. The details of the experimental design and results on the recent molecular line measurements will be presented