Microwave-Modulated Photon Doppler Velocimetry

Photon Doppler velocimetry (PDV) has become an important technique for explosives diagnostics over the last two decades. However, the inherent necessity for a very high-speed digitizer has rendered this technology expensive and inaccessible to the general research community. This letter reports a microwave-modulated PDV method, based on the conventional PDV testing, in which an RF modulator was used to directly modulate the current of a laser transmitter. Carrying the modulated frequency, the received PDV beat frequency was then engaged with a second beat frequency at the photo receiver, resulting in a low detection frequency. This resulting frequency can be detected using a digitizer with a lower sampling rate while retaining the information necessary for high-speed velocimetry measurement.