Abstract

The linewidth enhancement factor, also referred to as Henry factor or α factor, quantifies the intrinsic phase-amplitude coupling in a laser gain medium. Very extensive literature exists on measurement methods for semiconductor lasers, including direct estimation of the gain asymmetry, pump induced phase modulation (“AM/FM” method) and optical injection. Unfortunately none of these methods is well-suited for solid-state lasers, which feature slower dynamics and small values of α. Few measures are available in the literature: a value of α = 0.25 ± 0.13 was found in a Nd:YVO₄ laser, using injection and AM/FM modulation methods [1], and a surprisingly large α ≈ 1 was reported in Nd:YAG microchip lasers.

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