I will discuss how
coherent electromagnetic radiation at infrared and TeraHertz frequencies can be
used to drive collective excitations in solids nonlinearly. The driven
cooperative response can yield new types of functional control. I will
discuss experiments in which superconducting fluctuations can be amplified by
light at temperatures higher than the thermodynamic transition temperature. I
will also discuss the physics of superconducting plasmons in layered
superconductors and how these reveal new nonlinear THz phenomena.