Abstract

A traveling-wave amplifier made from a laser diode array by antireflection coating both facets has been shown to permit amplification of diode laser signals to high powers¹ and modulation of diode laser sources² while maintaining a single nearly diffraction-limited lobe in the far field. We have examined the far-field pattern in detail for a nearly plane-wave injected signal. The far field consists of a principal central lobe and either one or two sidelobes on opposite sides of the central lobe. The relative intensities in the sidelobes as a function of angle of incidence are consistent with volume diffraction effects from a gain grating created by the array. The detailed shape of the far field can be understood and modeled by the combined effects of the complex grating and the aperture formed by the array. The model allows the extraction of physical parameters of the amplifier, suggests a means of optimizing the amplifier structure, and indicates factors which might be important in understanding the behavior of gain-guided laser diode arrays.

© 1987 Optical Society of America