Accession Number : ADA195248

Title :   Ultrafast Processes and Spectroscopy with Free Electron Lasers.

Descriptive Note : Annual rept. 1 Jun 87-31 May 88,

Corporate Author : PRINCETON UNIV NJ DEPT OF ELECTRICAL ENGINEERING AND COMPUTER SCIENCE

Personal Author(s) : Fauchet, Philippe M

PDF Url : ADA195248

Report Date : Apr 1988

Pagination or Media Count : 4

Abstract : Femtosecond laser spectroscopy has been used to study carrier relaxation times in amorphous silicon. We find a relaxation time of 1 picosecond above the mobility edge and a relaxation time of 10 picoseconds in the bandtail states, after which temperature effects dominate the optical properties. Theoretical modeling of femtosecond spectroscopic measurements has also helped define what is measurable and what is not. Picosecond time-resolved reflectivity measurements have been performed during laser-induced phase transitions. The dielectric function of molten Si has been measured and superheating in the liquid phase has been observed to last at least 10 picoseconds. Work continues in both areas. We expect to expand the experimental program to other wavelengths thanks to the free electron laser. Keywords: Free electron laser; Time resolved spectroscopy; Amorphous semiconductors; Laser-induced phase transitions; Silicon.

Descriptors :   *SILICON, *LASER PUMPING, *EMISSION SPECTROSCOPY, AMORPHOUS MATERIALS, DIELECTRIC PROPERTIES, EDGES, FREE ELECTRON LASERS, HIGH RATE, LIQUID PHASES, MEASUREMENT, MOBILITY, MODELS, OPTICAL PROPERTIES, REFLECTIVITY, SEMICONDUCTORS, SPECTROSCOPY, SUPERHEATING, TEMPERATURE, THEORY, TIME, RELAXATION TIME

Subject Categories : Atomic and Molecular Physics and Spectroscopy

Distribution Statement : APPROVED FOR PUBLIC RELEASE