> However, if it's inside a plastic case that blocks light, it doesn't. You want an ordinary diode to allow current to flow easily when it senses light? Simple

> However, if it's inside a plastic case that blocks light, it doesn't. You want an ordinary diode to allow current to flow easily when it senses light? Simple: shine a powerful laser at the plastic-encased diode and it will melt the plastic and liquify the metal, fusing it together and allowing current to flow again. See? You just needed to try harder.