Anharmonically Excited Phonons as an Approach to Controlled Optical Materials: a First Principles Study*

Recent developments in the generation and control of intense ultrashort infrared radiation have provided a new approach to nonlinear optics through the coherent excitation of infrared active phonons to large amplitudes. Due to the large oscillating displacement of excited infrared phonons, Raman active phonons can be unidirectionally displaced though special nonlinear coupling terms. In contrast to the typical considerations of nonlinear optics where crystalline symmetry and light intensity dictate the dielectric response of the material, in this “nonlinear phononics” process alteration of the dielectric response is dictated by the symmetry and amplitude of the excited phonons. This provides a strategy for selective, ultrafast control of dielectric properties through infrared phonon excitation.

In this talk, I will discuss our recent theoretical effort towards ultrafast control of dielectric response through the excitation of infrared active phonons. I will highlight cases where the induced unidirectional Raman response is comparable to the excited infrared phonon amplitude.