Fiber-optic Beam Homogenizer

The output of the traditional optics fibers produce a Gaussian-shaped output due to the internal mode structure. Moreover, the output from traditional optical fibers contains spatial non-uniformities that are undesirable for certain applications. Many advanced applications require a “flat-top” intensity distribution of the laser beam as it produces uniform illumination and minimizes speckle. The Navy is seeking lightweight mid-infrared beam homogenizers capable to convert radiation from a multimode fiber to a flat-top beam. Among all-fiber techniques that use multimode fibers, flat top beam generation has only been demonstrated by fiber core shaping (fibers with e.g. square or rectangular cores). However the intensity profile of the beam maintains the same shape as the core and the rectangular or square beam shapes are difficult to efficiently integrate into existing circular-fiber based laser systems, resulting in significant loss of light. TIPD proposes to develop compact all-fiber low-loss circular-shaped homogenizer capable to operating across the 0.9-6 µm spectral range. TIPD’s homogenizers are based on novel infrared glass fibers with an advanced microstructured core design providing excellent mode mixing and a flat top beam output. The Phase I program will demonstrate the feasibility of developing such a novel all-fiber homogenizer for various Navy applications.