Coherent control of injection currents

When photons are absorbed by electrons in a material such as a semiconductor, the excited electrons tend to move in every direction, which typically causes the net electric current to vanish. Thus, linear optical absorption can be used to injected currents only in materials of very low lattice symmetry. However, it is possible to circumvent this restriction by exploiting a nonlinear effect involving two optical beams of different frequencies. Quantum interference of one- and two-photon absorption processes can lead to a non-zero injection current that can be controlled by the phases and polarizations of the incident optical beams. In this talk, an extension of this method to Quantum Interference control (QuIC) of two- and three-photon absorption processes will be presented, along with its application to lock an optical frequency comb that is not octave-spanning, which is an important step towards building a Direct On-chip Digital Optical Synthesizer.