I have Texas Instruments handbook on TTL Logic devices [~$25], or gates as they're commonly called. If you look at your motherboard you see these grey or brown things of rectangular shape edged with silvery leads mounted on the board.
A typical gate that is used everywhere, but usually in combination with another function in a gate, is a 2-input NAND [SN74LS01]. That is, two inputs, conforming to the boolean algebra equation set: 1*1 = 0, 1*0 = 1, 0*1 = 1, and 0 * 0 = 1. The transistor electric circuit diagram is quite complicated even for this simple NAND gate. Using light, and not concerning ourselves with a detailed diagram showing how the logic works, we can achieve the very same results using mirrors. That is, if the light is on = 1, then with two inputs we can generate the same results table in a gate as that listed above, using mirrors and filters only. That is, ON and ON will cause opacity within our gate and output OFF. ON and OFF will not cause opacity within our gate and output ON. &etc. I don't see why this has not even been mentioned before in the history of computer manufacture.
