Ultrafast Laser Spectroscopy

We have an in-house built Ti:sapphire laser capable of producing 20 fs, 4 nJ pulses at a repetition rate of 88 MHz.  A compact rotating-mirror autocorrelator has been developed to measure temporal width of the ultrafast laser pulses, see "A Compact Rotating-Mirror Autocorrelator Design for Femtosecond and Picosecond Laser Pulses," D. M. Riffe and A. J. Sabbah, Rev. Sci. Instrum. 69, 3099 (1998)

This laser has been used to study ultrafast electron and phonon dynamics near the Si(001) surface.  Publications in this area include the following:

"Measurement of Silicon Surface Recombination Velocity Using Ultrafast Pump-Probe Reflectivity in the Near Infrared," A. J. Sabbah and D. M. Riffe, J. Appl. Phys 88, 6954 (2000)

 "Temperature Dependence of Silicon Carrier Effective Masses with Application to Femtosecond Reflectivity Measurements," D. M. Riffe, J. Opt. Soc. Am. B 19, 1092 (2002)

 "Femtosecond Pump-Probe Reflectivity Study of Silicon Carrier Dynamics,"  A. J. Sabbah and D. M. Riffe, Phys. Rev. B 66, 165217 (2002).

"Coherent Excitation of the Optic Phonon in Si:  Transiently Stimulated Raman Scattering with a Finite-Lifetime Electronic Excitation," D. M. Riffe and A. J. Sabbbah, Phys. Rev. B 76, 085207 (2007).

We are currently studying LT-GaAs in order to identify the components of the ultrafast reflectivity.  LT-GaAs has application in ultrafast detectors and in THz spectroscopy.

Other ultrafast reflectivity measurements have been made on Au, Ag, Al, W, and Ta samples.  In Au we have used front-surface reflectivity measurements to probe the ballistic transport of hot holes away from the Au surface.  Data from the other metals is currently being analyzed.

Professor Mark Riffe and graduate student Ali Sabbah make adjustments to an ultrafast dynamics experiment.

 

Heart of the Ti:sapphire laser.  The Ti:sapphire crystal and two focusing mirrors are shown.  The green light is from the laser that is used to pump the Ti:sapphire oscillator.

 

 

 No, not a view from the ultrafast lab, but the Grand Tetons, which are a mere 200 miles north of Utah State University