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Time-resolved infrared spectroscopy (TRIR)


Three independent femtosecond laser systems used for generating ultrafast pulses in the mid-IR (and far infrared:THz) through the UV; infrared (InSb and MCT) and visible CCD multi-element focal plane array cameras and instrumentation for capturing transient spectra of samples with a single laser pulse; detection systems capable of making accurate time-resolved amplitude and phase measurements on THz pulses as they interact with samples; Optical parametric Amplifiers (OPA) and various nonlinear crystals for frequency conversion.

Kilohertz, Ti-sapphire time-resolved infrared apparatus

Kilohertz Ti-Sapphire time-resolved infrared (TRIR) apparatus using a 25 fs Kapteyn-Murnane oscillator seeded home-built regenerative amplifier (with compact stretcher-compressor and single Pockels cell design) pumped by either a 10 Watt Spectra Physics Evolution (background, left) or 25 Watt Empower system. The amplifier output (0.9 W at 80 fs FWHM) pumps a Spectra Physics OPA-800f (not shown) that generates tunable ~100 fs IR probe pulses by difference frequency mixing (DFM) in silver-gallium-sulfide (2.8 to 24 microns). Excitation of samples (in enclosed purged compartment at right) occurs via 400 nm or 267 nm harmonics of the regenerative amplifier (foreground). Difference transmission TRIR spectra across the DFM bandwidth are obtained by a computer-controlled scanning monochromator fitted with probe and reference broadband MCT detectors (top right; red).

pulsed dye-laser system

First broadband femtosecond TRIR pulsed Dye-laser based system with diode-pumped solid-state Nd:Vanadate, 2 Watt, 532 nm, 80 MHz pump for three independently tunable synchronous dye lasers. Home-built seeded 20 Hz Nd:YAG regenerative amplifier generates 25 mJ 532 nm pulses to pump three linear dye amplifier chains (ca. 0.7 to 1 mJ pulsed output energy) for UV excitation and difference frequency mixing mid-IR probe generation using LiIO3 DFM-crystal.

Mid-infrared pump-probe apparatus

Mid-infrared pump-probe apparatus including dual-beam probe normalization to reduce spectral intensity fluctuations and IR spectrograph outfitted with a cooled 256x256 InSb Focal Plane Array camera as the detector (upper left). Flowing liquid cell and raster scanning solid samples is available. In conjunction with an electronically timed Q-switched Nd:YAG system which delivers harmonic pump pulses, this system is capable of measuring molecular energy trnasfer and photochemical dynamics fro m150 femtosecond to millisecond time delays.


Associated Programs/Projects:


Name: Edwin Heilweil
Phone: 301-975-2370
Fax: 301-869-7682
100 Bureau Drive, M/S 8443
Gaithersburg, MD 20899-8443