HIGH-ORDER OPTICAL-HARMONIC GENERATION IN FILMS OF NONMETALLIC CRYSTALS

High-order optical-harmonic generation in nonmetallic films interactin g with pulses of laser light is examined. The wave functions of the cu rrent carriers in a crystal in an external electromagnetic field are c hosen in the form of Volkov-Keldysh solutions. An explicit expression for the intensity of the sth harmonic, which depends on the crystal pa rameters, is derived. A plateau and a cutoff effect, similar to those in the case of harmonic generation on an isolated atom, have been dete cted. Finally, numerical estimates are made for GaAs films excited by pulses of radiation from a carbon dioxide laser. (C) 1997 American Ins titute of Physics.