Wide field of view optics paired with large starer infrared detector arrays can be notoriously difficult to place into focus. This paper will discuss the lessons learned in taking one such system from being more than 20x out of its focus specification to within focus in a single iteration. Traditionally the tight tolerances required for space borne applications forces the system designer to carefully consider many effects that may otherwise be negligible. These include changes in system tolerances between ambient to cryogenic temperature, lens boule property differences, test setup to properly mimic the flight thermal profile, lack of commercially available lasers with the proper wavelength, and several others. In this case, some key pieces of information were not provided when the system arrived at Northrop Grumman’s Azusa facility for unit integration and through-focus testing. The presented approach involves taking extremely out-of-focus responses from point sources at various focus positions and combining them with optical modeling parameters to determine how to best reposition the detector array to the best plane of focus. A successful implementation of the approach will be presented using data from a wide field-of-view infrared sensor.
Here we present details of the design and performance of a family of compact, fiber-coupled, multi-bar, laser-diode stacks. The highest-power variant employs a pair of 6-bar stacks and a removable 400-μm, 0.22 NA fiber to deliver >400 W at 50 A. The overall power conversion efficiency (PCE) near 976-nm exceeds 40% at 400 W in CW operation with an uncoated delivery fiber. The brightest variant reaches a power density near 800-kW/cm<sup>2</sup> at 976-nm through a 200-μm, 0.22 NA fiber. Module variants have been built and characterized at multiple wavelengths between 780-nm and 980-nm. Applications for such modules include pumping of active fibers, pumping of rubidium vapor and direct material processing.