mode with the lowest threshold this mode changed from the fundamental to highest order and back to the fundamental mode as the cavity length was increased the behavior of these three regions is explained by the self imaging properties of the array at fractional talbot planes two embodiments of the invention were found suitable to achieve lateral mode control and hence for producing a single lobed far field diffraction pattern one embodiment is illustrated by fig3 a laser array 30 includes individual semiconductor lasers 32 44 spaced a distance d apart in the present demonstration d 50 u03bcm the output facets of the lasers are provided with an antireflection coating suitable lasers are algaas diode lasers made by spectra diode laboratory which operate at a wavelength of 0 8 u03bcm it will be appreciated by those skilled in the art that the number of lasers shown in fig3 is entirely exemplary and that an array would generally include many more lasers in addition other types of lasers could be used at other wavelengths e g ingaasp at 1 3 u03bcm in the present demonstration a one dimensional laser array consisting of seven gain guided multiple quantum well lasers was utilized in experiments at the lincoln laboratory of the massachusetts institute of technology but the concept can be extended to hundreds of lasers in two dimensions a microlens array 46 is interposed to intercept the beams the lenslet array 46 to be described in more detail in conjunction with fig4 below collimates each of the individual beams after collimation a portion of the light is reflected from a partially reflecting feedback mirror.