Contrast this with standard methods where one passes a light beam through a cell into a detector, looking for a small change in a large signal.
Hats off to the Michigan team for this very clever (and unnerving) demonstration.
The thermal effect is one, where the membrane heats up and makes the surrounding air expand. The other is the light hitting photosensitive electronic components.
Discussed here: https://news.ycombinator.com/item?id=21445043
Light pressure of sunlight is about 1mg/m^2. Or one nanogram per square millimeter, a reasonable size for a chip microphone. Will chip microphones respond to a nanogram of pressure?
Because the more efficient way would be to just make use of the backdoors directly or force Amazon/Google to give you an eavesdropping API. All in the name of national security, of course.
I've always wondered how it's possible for smartphones to sound so good given that the microphone needs to fit in a few millimeters, how do they sound better than much bigger (cheap) microphones. Apparently the answer is MEMS microphones.
Holy shit, this might be even more astounding to me than the laser attack itself.