Switching ultrastrong light-matter coupling on a subcycle scale

Intersubband cavity polaritons in a quantum well waveguide structure are optically generated within less than one cycle of light by a 12-femtosecond near-infrared pulse. Mid-infrared probe transients trace the nonadiabatic switch-on of ultrastrong light-matter coupling and the conversion of bare photons into cavity polaritons directly in the time domain. Future perspectives of room-temperature subcycle control of ultrastrong electron-photon interaction are discussed. (C) 2011 American Institute of Physics. [doi :10.1063/1.3578341]