Research Overview
I explore physical phenomena on their natural timescales by developing innovative, simple-to-implement techniques that study the interaction of complex materials with light. The strong interactions between complex materials and light are often mediated by attosecond-to-femotsecond proecess that unfold over nanoscale volumes.
I do this using ultrafast lasers and nanoscale devices.
What is ultrafast?
An ultrafast laser produces very short pulses that are on the order of few femtoseconds in duration. A femtosecond is 10-15 of a second, or 0.000000000000001 s. For comparison, if a femtosecond were the same length in time as a second, then a second would be the same length in time as roughly the age of the earth.
There are two main reasons for using ultrafast laser pulses:
- Observing very fast time scales: Ultrafast pulses can act like a “strobe” light. This can be used to follow natural phenomena on their intrinsic timescales, such as chemical reactions and electron dynamics.
- Achieving high peak fields: Since the pulses are very short, we can pack a lot of energy into each pulse without the need for special amplifiers or extra equipment, and can therefore investigate physical phenomenon that occur in intense environments. This is called the "strong-field regime".
Why nanoscale?
Working in the nanoscale allows visualization of the small building blocks of nature. At the surface of nanostructures, a natural field enhancement occurs due to small, sharp geometric shape of the structure. This means that an optical field is amplified simply due the shape of the structure, and thus does not need to be as intense to reach the strong-field regime. This geometric field enhancement is caused by the dielectric constant discontinuity at the metal/vacuum interface. This leads to an accumulation of charge just under the surface which creates a strong local field due to the small size of the structure. Other sub-wavelength effects, such as plasmonic resonances, can considerably add to this field enhancement in materials such as silver or gold. These resonances are highly material, shape and wavelength dependent. Additionally, at the nanoscale level, materials and structures can be engineered to exhibit interesting new properties, some based on quantum mechanical effect.