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The ability to directly image ultrafast phenomena with nanometer spatial resolution is essential to our understanding of local excitation dynamics in nanomaterials and devices. We have developed a new approach to ultrafast scanning tunneling microscopy (STM) that couples terahertz (THz) pulses to the scanning tip of a STM. We have used THz-STM under ambient lab conditions to image ultrafast charging...
An ultrafast terahertz (THz) pulse coupled to the tunnel junction of a scanning tunnelling microscope (STM) is found to produce a subpicosecond rectified current pulse that can be detected by the STM electronics. We use these THz-induced current pulses to develop a new type of ultrafast STM and demonstrate its unprecedented simultaneous 2 nm spatial resolution and 500 fs temporal resolution under...
We directly image terahertz waves generated by optical rectification of tilted-pulse-front optical pulses in LiNbO3. The terahertz generation efficiency is highest when the pump-pulse tilt angle is equal to the THz Cherenkov angle.
Terahertz time-domain spectroscopy is used to measure the temperature-dependent refractive index of heavy oils down to 80 K. Evidence for a glass transition is observed, providing insight into the viscosity-temperature behavior of heavy oils.
Nonlinear dynamics of free-carriers in direct bandgap semiconductors at terahertz (THz) frequencies is studied using high power, few-cycle pulses. The physical mechanisms that give rise to such dynamics will be discussed in details.
Nonlinear dynamics of free-carriers in direct bandgap semiconductors at terahertz (THz) frequencies is studied using high power, few-cycle pulses. Techniques as Z-scan and THz-pump/THz-probe are employed to explore nonlinear interactions in both n-doped and photoexcited systems. The physical mechanism that gives rise to such interactions will be discussed in details.
We study ultrafast hot electron transport in n-doped InGaAs using polarization-sensitive nonlinear THz-pump/THz-probe spectroscopy. We observe an anisotropic effective mass for hot electrons due to the nonparabolicity of the conduction band.
Nonlinear dynamics of free carriers in direct bandgap semiconductors at terahertz (THz) frequencies is studied using the intense few-cycle source available at the Advanced Laser Light Source (ALLS). Techniques such as Z-scan and optical-pump/THz-probe are employed to explore nonlinear interactions in an n-doped InGaAs thin film and a photoexcited GaAs sample, respectively. The physical mechanism that...
There is intense and growing interest in one-dimensional (1-D) nanostructures from the perspective of their synthesis and unique properties, especially with respect to their excellent optical response and an ability to form heterostructures. This review discusses alternative approaches to preparation and organization of such structures, and their potential properties. In particular, molecular-scale...
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