How does this LASER POWER METER work?

This laser power meter has a very interesting method of operation. This is our first laser power meter, so everything is new to us. @brainiac75 Video https://www.youtube.com/watch?v=wFC9b1a32r4 00:00 Introduction 02:04 Testing 08:03 Teardown 10:15 How it works 16:05 Summary 18:47 Closeout