Accession Number : AD0670199

Title :   INVESTIGATION OF MODE-LOCKING AND CERTAIN OTHER MECHANISMS IN LASERS AND THEIR IMPLICATIONS.

Descriptive Note : Final rept. Jan-Dec 67,

Corporate Author : RAYTHEON CO WALTHAM MASS RESEARCH DIV

Personal Author(s) : Statz,H. ; deMars,G. A. ; Bass,M.

Report Date : JUN 1968

Pagination or Media Count : 95

Abstract : In the report we investigate the basic mechanisms that lead to mode locking in lasers and to the formation of ultrashort pulses. We find that in lasers nonlinear polarizations are produced at the so-called combination tone frequencies which act much like externally injected signals. When the amplitudes of the combination tone polarizations are large enough, the various modes may lock onto them and definite phase relationships between these modes are established. The amplitudes of the source polarization terms are proportional to the third power of the electric field and thus locking depends upon the power level of the laser. Furthermore, the nonlinear polarization is proportional to the fourth power of the dipole matrix element between the two states in question and thus depends strongly on the radiative lifetime of the upper laser state. It is thus clear why a short lifetime saturable absorber is very effective in producing self locking. It can also be shown that a mode-locked laser emits more radiation than an oscillator with random phases. Also investigates mode suppression in ring lasers and related devices. It is found that for sufficiently large splittings of a given longitudinal mode, one of the split-off components tends to become suppressed. This is due to the fact that the gain in one of the modes is significantly lower. Mode suppression of this type is investigated in Nd(3+) - doped YAG lasers. (Author)

Descriptors :   (*LASERS, ELECTROMAGNETIC PULSES), ARGON, POLARIZATION, MAGNETOOPTICS, ELECTRIC FIELDS, OSCILLATION, DETECTION, ABSORPTION, DISCHARGE TUBES, SOURCES, PHASE STUDIES, SCATTERING, GAS LASERS, NEODYMIUM, ATOMIC ENERGY LEVELS, OPTICAL PUMPING, CRYSTAL DEFECTS, GARNET

Subject Categories : Lasers and Masers

Distribution Statement : APPROVED FOR PUBLIC RELEASE