Mode structure and the noise performance of a gain-guided amplifier

Abstract

The spatial structure of a gain-guided amplifier is naturally described by a set of nonorthogonal modes. We present an analysis of the mode structure of an amplifier with a focused Gaussian gain. It is found that the modes are spatially narrower and have a different radius of curvature than the corresponding free-space modes. A calculation of the signal-to-noise ratio shows that the spatial structure of the input field has a significant effect on the amplifier noise performance.PACS number(s): 42.60.Da, 42.65.Dr