Optimal shape for manipulation via telekinetic light
I have a species that can emit beams of light from their bodies (think flashlight). If the light lands on an object, they can telekinetically manipulate that object (pull, push, lift, etc.). Now bear with me: the telekinetic force applied to the object occurs at the point of light absorption. Considering an opaque black sphere, for example, the force would be applied along the outer surface on the side catching this light beam. A translucent sphere would absorb light throughout, which would mean force could be applied to the entire volume of the object. A transparent sphere would work similarly, except some light would leak out the far side and therefore be wasted. A reflective sphere would also waste light.
Over generations and generations, this species has developed a specific shape that works optimally with their powers. This ideal shape absorbs as much light as possible, since any light not absorbed is wasted. The shape also absorbs light in such a way that the net force is applied as close to the center of mass as possible. Assume that the object can be kept at a specific orientation in relation to the light beam. Also assume that the object is made from material that can be any color and transparency level throughout its volume. 302
What would this optimal shape be?
For my own part, I have two tentative designs that I think illustrate this problem:
1. A cone that starts with a transparent point and transitions smoothly to a completely black, opaque base. The cone is oriented such that the light beam enters at the clear point and is fully absorbed by the time it reaches the base. With this design, I worry about light leaking out the sides of the cone, which brings me to my second design.
2. A sphere with a primarily black, opaque surface. There is a single transparent entry point for the light beam, somewhat like an eye. The internal makeup transitions smoothly from that transparent entry point to black and opaque. I believe this design absorbs more light than the cone, but would likely be heavier, which may not be a good tradeoff.
Both of my solutions ignore that "transparent" typically means "reflective," which would waste light. I can imagine there are more exotic solutions like shapes utilizing hollow cavities, "egg carton" surfaces, or structural coloration: I am absolutely interested in these types of designs if anyone is feeling their oats, but I recognize that this strays pretty heavily into light physics territory. Mostly I'm wondering if there are key improvements that could be made to either of my designs, or if there are other somewhat obvious designs that would work better. This shape has a high level of cultural and technological importance to this species, so I really want to give it my due diligence. Thanks! 302