An apparatus includes a center portion and a plurality of spoke portions that are in contact with the center portion and that extend to a perimeter region. The plurality of spoke portions include at least a first monolithic spoke portion extending from the center portion to the perimeter region, and the center portion and the plurality of spoke portions define a plurality of cavity regions among the plurality of spoke portions. The center portion, the plurality of spoke portions, and the plurality of cavity regions are included in a gradient index (GRIN) lens having a plurality of effective dielectric constants that are based on a radial distance from the center portion.