Ultrafast bandgap photonics

It is well known that ultra-short pulse is able to change physical state of condensed matter: to melt, to evaporate, to ionize. It is less known that ultra-short pulse is able to change optical state -transmittance, reflectivity and polarization characteristics. In the same time a fact that ultra-short pulse may not change observable electronic state of the media passed practically unnoticed. Combination of the effects most pronounced in semiconductors were bandgap amplifies it in highly non-linear way. Changes in optical state are induced on the time scale comparable with pulse dwell time, but these changes last on the scale comparable with recombination time and depend on bandgap structure. Therefore we are introducing the term - Ultrafast Bandgap Photonics . When ultra-fast laser induces non-linear absorption, then Ultrafast Bandgap Photonic effects may be observed if combination of pulse dwell time, energy per pulse and pulse repetition rate satisfy very specific requirement. Ultrafast bandgap photonics is an optical and electronic phenomenon that changes spectral reflectivity, and transmittance as well as polarization characteristics when electronic structure of matter changes. Ultrafast Bandgap Photonics depends on pulse characteristics and bandgap structure. Ultrafast Bandgap Photonic effects are reversible and may not change physical state of media. Applications of Ultra-fast bandgap photonics are control of semiconductor characteristics and material properties. That includes, but is not limited, optically induced superconductivity, remote sensing and counter-sensing of all kind, laser cooling, bandgap material characteristics management. In this paper we discuss some foundations of ultra-fast bandgap photonics.