Mode degeneracies and the Petermann excess-noise factor for unstable lasers

被引:109
作者
Berry, MV [1 ]
机构
[1] Univ Bristol, HH Wills Phys Lab, Bristol BS8 1TL, Avon, England
关键词
D O I
10.1080/09500340210135402
中图分类号
O43 [光学];
学科分类号
070207 ; 0803 ;
摘要
The linewidth of an unstable laser exceeds the quantum minimum by the Petermann factor K, which depends on the overlap between left and right eigenvectors of the (non-unitary) round-trip wave operator. When K is plotted as a function of the Fresnel number N, strong resonances occur, which are associated with degeneracies N-c lying close to the real axis in the complex N plane. For certain values of the magnification, degeneracies can lie on the real axis, and K is infinite. The Horwitz Southwell asymptotic theory of the spectrum, presented here in a very accurate form and with a streamlined derivation, is used to show that the peaks occur near N = s - 1/8 ( s integer), and to give reliable formulae for the resonance widths Im N-c and other features of the degeneracies. Low-lying resonances have discontinuous profiles associated with mode switching where the absolute values of the eigenvalues cross (these are not degeneracies).
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页码:63 / 81
页数:19
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