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We describe the development of a broadband (0.3-10 THz) optical pump-terahertz probe spectrometer with an unprecedented combination of temporal resolution (≤200 fs) operating in external magnetic fields as high as 25 T using the new Split Florida-Helix magnet system. Using this new instrument, we measure the transient dynamics in a gallium arsenide four-quantum well sample after photoexcitation at 800 nm.

We have demonstrated that micron-size silica beads can be arranged in desired synthetic structure using an optical tweezer in a saline buffered solution. In 3.1 µm silica and water solution we added the right proportion of antistick glycol and NaCl to form a solution in which silica beads brought close to one another can bind by an adhesive electrostatic force without drifting away due to their thermal energy. Then by trapping and dragging one bead at a time using an optical tweezer, we have arranged the silica beads in two-dimensional structures.

We have conducted pump-probe spectroscopy of bulk GaAs in the Split Florida-Helix at 15 K and 25 T. We observe an electronic rise followed by a slower decay with a superimposed oscillatory response.

We have performed high-fluence, nondegenerate pump-probe spectroscopy in the Split Florida-Helix magnet at 25 T and 15 K. The electronic component of our ultrafast differential reflectivity can be described with a simplified four-level approximation to determine the scattering and recombination rates. Ultrafast oscillations are well described by a coherent acoustic phonon model. Our free-space ultrafast spectroscopic technique will permit future experimental investigations to study novel photoinduced phase transitions and complex interactions in correlated electron systems, which will require the high pulse energies of our free-space alternative.

We demonstrate that various features of a complex GaAs/AlGaAs heterostructure superlattice can be resolved using coherent acoustic phonon spectroscopy (CAP) and that CAP is a viable non-destructive metrological tool in the study of stratified media.

Using THz-time-domain magneto-spectroscopy, we have studied the dynamics of a 2DEG (3.4×106 cm2 V−1 s−1) as a function of temperature (0.4 K–100 K). The decoherence lifetimes increase monotonically as temperature decreases below 1 K. We will discuss the mechanisms that contribute to the lifetimes.

We use ultrafast terahertz spectroscopy to study the magnetoconductivity tensor of a 2DEG as a function of temperature (0.4 K-100 K). The magnetoconductivity line width decreases monotonically with temperature.

We have studied the dynamics of a high mobility two-dimensional electron gas as a function of temperature. The presence of satellite reflections in the sample and magnet can be modeled in the time-domain.