The technique of using a light beam to remotely record sound probably originated with Léon Theremin in the Soviet Union at or before 1947, when he developed and used the Buran eavesdropping system.
[1] This worked by using a low power infrared beam (not a laser) from a distance to detect the sound vibrations in the glass windows.
[1][2] Lavrentiy Beria, head of the KGB, had used this Buran device to spy on the U.S., British, and French embassies in Moscow.
[2] On 25 August 2009, U.S. patent 7,580,533 was issued for a device that uses a laser beam and smoke or vapor to detect sound vibrations in free air ("Particulate Flow Detection Microphone based on a laser-photocell pair with a moving stream of smoke or vapor in the laser beam's path").
Sound pressure waves cause disturbances in the smoke that in turn cause variations in the amount of laser light reaching the photo detector.