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| Delivery of audible messages via photoacoustics. (a) Traditional photoacoustic configuration: 1907.2 nm laser light is absorbed by ambient water vapor. The laser beam is amplitude modulated via an acousto-optic modulator. (b) Dynamic photoacoustic communication amplifies the audible signal. (c) H2O absorptivity near 1.9 μm, with an overlay of the laser emission from our thulium fiber laser. Image: MIT Lincoln Laboratory / Optics Letters. |
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