Research Projects
Muli Phase Interferometric scattering
The detection of a single molecule via its luminescence is practiced for many decades by now. The detection of individual particles which do not emit light is much more challenging. Sandoghdar introduced Interferometric scattering microscopy (iSCAT), a method for detecting the light scattered from nanoparticles, enhanced it by interfering it with a reference light beam reflected from a surface. Our new approach which enables to control the phase between the scattering and interference, and to combine 2-3 measurements with different phases, enables to increase dramatically the detection and the image contrast of nanometric particles.
Absorption spectroscopy of Hexagonal Silicon
Silicon, the most widely used semiconductors in electronics, plays also a central role in solar cells and a myriad of optoelectronic devices. The unstable hexagonal structure of silicon is predicted to possess superior optical properties. It was recently successfully grown by Bekkers and coworkers as hexagonal silicon nanowire shells grown on a template of gallium phosphide. Measuring its absorption spectra presents a significant challenge. In our group we use a integrating sphere to measure the absorption spectra of individual hexagonal silicon nanowires. These optical properties and photoconduction measurements will elucidate the absorption efficiency of the hexagonal structure.
Ultrafast dynamics of Nano-Objects
Measuring the change in reflectivity (ΔR) using the traditional pump-probe approach can monitor photoinduced ultrafast dynamics in matter, yet relating these dynamic to physical processes for complex systems is not unique. By applying a simple modification to the classical pump-probe technique, we simultaneously measure both the first and second order of ΔR. These additional data impose new constraints on the interpretation of the underlying ultrafast dynamics. In the first application of the approach, we probe the dynamics induced by a pump laser on the local-surface plasmon resonance (LSPR) in gold nanoantennas. Measurements of ΔR over several picoseconds and a wide range of probe wavelengths around the LSPR peak are followed by data fitting using the two temperature model. The constraints, imposed by the second-order data, lead us to modify the model and force us to include the contribution of nonthermalized electrons in the early stages of the dynamics.
