Ultrafast Processes and Spectroscopy with Free Electron Lasers.

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.

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Document Details

Document Type
Technical Report
Publication Date
Apr 01, 1988
Accession Number
ADA195248

Entities

People

  • Philippe M. Fauchet

Organizations

  • Princeton University

Tags

DTIC Thesaurus Topics

  • Electrical Engineering
  • Electrons
  • Engineering
  • Femtosecond Time
  • Free Electron Lasers
  • Free Electrons
  • Laser Spectroscopy
  • Lasers
  • Materials
  • Measurement
  • Optical Properties
  • Phase Transformations
  • Picosecond Time
  • Relaxation Time
  • Scheduling (Production)
  • Semiconductors
  • Spectroscopy

Fields of Study

  • Physics

Readers

  • Optical Physics and Photonics.
  • Quantum Dot Semiconductor Device Photonics and Graphene Optoelectronic Materials and THz Physics.
  • Thin Film Deposition Science.

Technology Areas

  • Directed Energy
  • Directed Energy - Lasers
  • Microelectronics
  • Microelectronics - Graphene