Someone will be much much better for explaining why Sputtered Titanium is seen to be the most optimal for creating a Form that will be beneficial to a Optical Read of a Shadow????
Nobody except you just now has mentioned sputtered titanium, and certainly not in the context of DS Audio optical cartridges which exclusively use aluminium alloys for their bodies. (They do have mono cartridges which incorporate a brass footer).
In fact, you were the first to mention titanium in this context. There is a world of difference between sputtering, in which material is randomly sprayed at a surface, and laser fusion which precisely sinters particles together in 3-d space, a bit like 3-d printing.
why does a modern design Optical Read Cart', need a Diamond Cantilever or other materials renowned for being exceptional when used as conduits for managing transferred kinetic energy
In your terms, the "Shadow" being "Read" is created by a shade plate attached to the cantilever as described by @dogberry. You can see pictures here DS Audio - please scroll down to Details.
Kinetic energy is transmitted to the shade plate, which makes it move relative to the cartridge body. Ideally it moves precisely in synchronicity with the stylus, which ideally tracks precisely the modulations in the groove. As a purely mechanical system up to this point, it is subject to stresses and strains. Stresses are forces, and strains the deformations always caused by those stresses. Acceleration of the stylus can be huge, reaching thousands of Gs where G is the acceleration caused by gravity at the earth's surface. Materials and mechanical design influence how well the shade plate actually moves with the stylus, and how well the stylus actually responds to the groove.
Mechanical systems are also subject to vibrations and resonances. Cartridges, if designed to be neutral, channel these vibrations away from the stylus / body interface. Many cartridges are not designed to be neutral, but to add pleasing colourations of their own. If that is what you want, DS Audio is probably not for you, but I digress.
So now, we have a shade plate which moves. From this point on you can forget about energy transfer altogether, because the energy of the light source comes from an external DC power supply, not from the record. One of the functions of the Equalizer is to provide clean DC power.
As the shade plate moves, the shadow it casts on the photoreceptor changes in area, varying the number of photons absorbed and hence modulating the output signal, which varies with the position of the shade plate and not its acceleration.
This is a slight simplification because in current DS Audio stereo cartridges, there are two light sources and two photoreceptors, plus one shade plate with two "wings".
How does the DC power get from the Equalizer to the diodes in the cartridge? A cunning 'steal' from conventional cartridge wiring design, which uses four separate wires, allowing each channel to be balanced. Most phono inputs are not balanced however, so DS Audio use two of the wires to carry DC and neutral.
I believe DS Audio is working on cabling to carry balanced cartridge output and power, but this will likely require tonearms to be rewired or custom designed.