Abstract

A spatial filter (a series of 3.1-µm slits, 10.42-µm center-to-center spacing) has been placed at the Fourier plane of five external cavity diode lasers as illustrated in Fig. 1. The five antireflection-coated diode lasers are focused onto the spatial filter and then reimaged by a second lens onto a partially reflecting plane mirror at the other end of the cavity. Since all the distances between objects and lenses correspond to the focal lengths of the respective lenses, the radiation from the diode lasers undergoes a Fourier transform four times as it makes the round trip through the cavity. An ideal spatial filter, the exact Fourier transform of the laser diode array, would specify operation at a wavelength uniquely determined by the geometrical spacings of the array and the spatial filter.

© 1986 Optical Society of America