How fast electrons and photons mix: Sub-cycle switching of intersubband cavity polaritons

Intersubband cavity polaritons in a quantum well waveguide structure are optically generated within less than one cycle of light by a femtosecond near-infrared pulse. Mid-infrared probe transients trace the non-adiabatic switch-on of ultrastrong light-matter coupling and the conversion of bare photons into cavity polaritons directly in the time domain.