you're building a photo phone using light to communicate so his idea was to encode the voice or music into a lie beam then propagate a lie beam in space convert light back into sound again you cannot you hear that so he had no access to laser at a time that he was way be the head of the time you know because laser was invented in the 50s right so he had to use sunlight to demonstrate this principle now this idea never quite took off right for reasons you can imagine because together to work you have to have a line of sight