High-precision measurement of optical frequency differences between Q-switched laser pulses using photo-electromotive-force sensors

We demonstrate the measurement of optical frequency differences between Q-switched laser pulses by using photo-electromotive-force (photo-EMF) optical frequency sensors. The presence of high-peak-power laser pulses affords the photo-EMF frequency sensor with ultrafast response times limited only by the free-carrier lifetime of the sensor material. Such fast response times lead to a broad dynamic range for optical difference frequency measurements with an experimentally demonstrated frequency detection bandwidth in excess of 50 MHz, limited only by the capability of our test equipment. Such a large dynamic range for optical frequency detection makes photo-EMF sensors ideal candidates for adaptive remote sensing of high-speed objects.