Laser Microphone
It’s all too easy to listen to someone’s conversation using little more than a laser beam. Laser microphones use a laser beam to measure the vibration of sounds on a surface, usually glass windows, transmitting those sounds back to the listener’s receiver. DIY instructions abound on the internet, including this tutorial by Lucid

激光窃听器
用这个装置发射激光束，通过监测窗户玻璃的振动可以将其转化为声波，发送到监听者的接收机上。印象中煎蛋发过但我找不到了。