Mode splitting and coherent instabilities in high gain lasers

Thesis/Dissertation · Fri Jan 01 04:00:00 EST 1982

OSTI ID:6762847

Minden, M L

A continuous wave laser composed of a lossy cavity and an active medium with a narrow homogeneous linewidth may exhibit an output instability in the form of a periodic pulse train or chaotic signal. In the time domain, the instability is interpreted as the inability of the medium polarization to respond quickly to perturbations in the optical field of the cavity. In the frequency domain it is seen to arise from the splitting of a single longitudinal mode into several oscillating lines, each of which satisfies the same cavity resonance conditions as the original mode. The instability is most easily observed in a laser with an inhomogeneously broadened medium. Under appropriate conditions, candidate laser systems include chemical lasers, far-infrared molecular lasers, CO/sub 2/, iodine, and helium-neon (3.39 ..mu..m) as well as the intensively studied xenon and helium-xenon lasers. In this work the mode splitting interpretation of the instability is shown to yield a new understanding of the complex behavior reported in xenon and helium-xenon lasers. The fundamental frequencies of the instability and the possibility of chaotic output are shown to be determined by unequally spaced resonant modes which arise close to the laser threshold. With saturation, non-resonant harmonics of the fundamental frequencies appear in the laser output. These harmonics have fixed phases relative to the resonant modes and lead to the complex asymmetries of the pulse shapes. Interaction between the resonant and non-resonant modes can trigger period doubling in the pulse train.

• OSTI ID: 6762847
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
420300* -- Engineering-- Lasers-- (-1989)
AMPLIFICATION
CARBON DIOXIDE LASERS
CHEMICAL LASERS
CONTROL
GAIN
GAS LASERS
HELIUM-NEON LASERS
HELIUM-XENON LASERS
INSTABILITY
LASERS
MODE CONTROL
MODE SELECTION
POLARIZATION