The spontaneous emission factor for lasers with gain induced waveguiding

Journal Article · Thu Nov 01 04:00:00 EST 1984 · IEEE J. Quant. Electron.; (United States)

DOI:https://doi.org/10.1109/JQE.1984.1072305· OSTI ID:5893040

Newstein, M

The expression for the spontaneous emission factor for lasers with gain induced waveguiding has a factor K, called by Petermann ''the astigmatism parameter.'' This factor has been invoked to explain spectral and dynamic characteristics of this class of lasers. We contend that the widely accepted form of the K factor is based on a derivation which is not appropriate for the typical laser situation where the spontaneous emission factor is much smaller than unity. An alternative derivation is presented which leads to a different form for the K factor. The new expression predicts much smaller values under conditions where the previous theory gave values large compared to unity. Petermann's form for the K factor is shown to be relevant to large gain linear amplifiers where the power is amplified spontaneous emission noise. The expression for the power output has Petermann's value of K as a factor. The difference in the two situations is that in the laser oscillator the typical atom of interest couples a small portion of its incoherent spontaneous emission into the dominant mode, whereas in the amplifier only the atoms at the input end are important as sources and their output is converted to a greater degree into the dominant mode through the propagation process. In this analysis the authors use a classical model of radiating point dipoles in a continuous medium characterized by a complex permittivity. Since uncritical use of this model will lead to infinite radiation resistance they address the problem of its self-consistency.

• Research Organization: Polytechnic Institute of New York, Long Island Center, Farmingdale, NY 11735
• OSTI ID: 5893040
• Journal Information: IEEE J. Quant. Electron.; (United States), Journal Name: IEEE J. Quant. Electron.; (United States) Vol. QE-20:11; ISSN IEJQA
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
420300* -- Engineering-- Lasers-- (-1989)
AMPLIFICATION
AMPLIFIERS
CALCULATION METHODS
DIPOLES
DYNAMICS
ELECTRONIC EQUIPMENT
EMISSION
EQUIPMENT
GAIN
LASERS
MATHEMATICAL MODELS
MECHANICS
MULTIPOLES
NOISE
OSCILLATORS
SPECTRA
WAVE PROPAGATION
WAVEGUIDES