OBSERVATION OF RADIATION FROM NONLINEAR POLARIZATION SIDEBAND IN ARGON LASERS

Abstract

An argon laser oscillating at 4880 and 5145 Å, when the cavity lengths for the two transitions have been made unequal, shows anomalous beat notes in the 4880 Å line which correspond to mode spacing characteristic of the 5145 Å line, and similarly, the 5145 Å line beat spectrum contains frequencies belonging to the 4880 Å cavity. These observations are quantitatively explained by radiation from nonlinear polarization sidebands. The interaction between the lines occurs via their common lower laser state. Nonlinear polarization sidebands have been postulated in the past to be responsible for mode‐locking phenomena and the generation of ultrashort pulses, but their direct observation in conventional lasers is, in general, difficult since the polarization sidebands coincide with cavity modes.