High-order optical-harmonic generation in films of nonmetallic crystals

High-order optical-harmonic generation in nonmetallic films interacting with pulses of laser light is examined. The wave functions of the current carriers in a crystal in an external electromagnetic field are chosen in the form of Volkov-Keldysh solutions. An explicit expression for the intensity of the sth harmonic, which depends on the crystal parameters, is derived. A plateau and a cutoff effect, similar to those in the case of harmonic generation on an isolated atom, have been detected. Finally, numerical estimates are made for GaAs films excited by pulses of radiation from a carbon dioxide laser.