Abstract: A compact, inexpensive and rugged fiber collimating lens and lens array achieve large beam diameters and provide long working distances. A special single-mode fiber is inserted between a standard single-mode input fiber and a GRIN fiber lens, typically quarter-pitch or slightly longer. The specialty fiber condenses the mode field diameter (MFD) of the beam in the input fiber into its smaller MFD. As a result, the fiber collimating lens provides greater beam expansion due to the larger divergence angle of the specialty fiber, which in turn provides longer working distances.

Abstract: A method for fabricating gradient-index rods and rod arrays. A central rod of optical glass having predetermined properties and predetermined outside dimensions is placed inside a tube of optical glass having predetermined properties and predetermined outside dimensions, to form an assembly. The inside dimensions of the tube are substantially equal to the outside dimensions of the rod. The tube is formed of a plurality of coaxial sleeves, the outside dimensions of each interior sleeve being substantially equal to the inside dimensions of the next adjacent sleeve, each sleeve having a selected refractive index so that, together with the tube, the refractive indices from the central rod through the outermost sleeve approximate the refractive index profile of the gradient-index rod to be fabricated. The central rod and sleeve material is selected so that their respective thermal indices of expansion are substantially equal.