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Accession Number:
AD0670199
Title:
INVESTIGATION OF MODE-LOCKING AND CERTAIN OTHER MECHANISMS IN LASERS AND THEIR IMPLICATIONS.
Corporate Author:
RAYTHEON CO WALTHAM MASS RESEARCH DIV
Report Date:
1968-06-01
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 Nd3 - doped YAG lasers. Author
Descriptive Note:
Final rept. Jan-Dec 67,
Pages:
0095
Contract Number:
F19628-67-C-0252
File Size:
0.00MB
