Second-Harmonic Light from the Interaction of a Nanosecond CO2Laser Pulse with the Plasma Produced from Polyethylene Sheet

Abstract
A 4-J, 10.6-μm, pulsed (2 nsec), CO2 laser has produced small amounts (4 × 107 of incident fundamental) of second-harmonic back emission (5.3 μm) with a definite threshold at about 1 J. Any three-halves frequency emission (7.07 μm) is at least 50 times fainter than the second harmonic. This is consistent with theoretical concepts.