Laser Laboratory

The Wasielewski Group’s laser laboratory has two high repetition rate amplified femtosecond laser systems, each having Ti:sapphire femtosecond oscillators that produce 25 fs pulses centered at 800 nm. System 1 has a laboratory-built regenerative amplifier, which produces 80-100 fs, 0.8 mJ pulses at a 1 kHz repetition rate. The output of System 1 drives an optical parametric amplifier that generates wavelengths from 460-2000 nm. System 1 is equipped for transient absorption experiments using a CCD detector, and has a 150 fs overall instrument response function. System 2 has a Spectra-Physics Spitfire short-pulse regenerative amplifier that routinely produces 35 fs, 1.2 mJ, 800 nm pulses at a 1 kHz repetition rate. The output of System 2 drives an optical parametric amplifier that generates 460-2000 nm, 50 fs pulses at a 1 kHz repetition rate. System 2 is equipped for both transient absorption and stimulated Raman spectroscopy with an instrument response function of 50-70 fs.

A third cavity-dumped femtosecond Ti-sapphire oscillator provides 25 fs, 800 nm pulses at a variable repetition rate that is frequency doubled. This laser is used principally for time-resolved fluorescence measurements. A Hamamatsu Streakscope is used to determine time-resolved fluorescence spectra with a time resolution of about 5 ps. Time-resolved fluorescence microscopy as well as AFM is performed with a Digital Instruments combination confocal/AFM microscope system. This microscope is equipped with a LaVision photon-counting imaging camera that can record 512 x 512 pixel fluorescence images with 100 ps time resolution.

For transient absorption and emission measurements on a nanosecond time scale or longer a Continuum Q-switched, 10 ns pulse Nd-YAG/OPO laser combination is used.