Time programmable frequency combs (IMAGE)
Caption
Distance measurement using dual frequency combs requires tight coordination between the pulse timing of the two combs. The pulses from one comb laser, F1, are bounced off a faraway object, and the second comb (upper F2 example), which is slightly offset in repetition period, measures their return timing with great accuracy. However, by nature of this approach, the detector can only register photons from the F1 ranging laser that arrive at the same time as pulses from F2. Any photons that arrive between the overlaps, as do the pulses in the upper F2 example, are lost information. The team’s innovation incorporates a digital controller that can adjust the time output such that the F2 comb’s pulses speed up or slow down, as represented by the moving pulses in the lower F2 example. This time adjustment allows the two combs’ pulses to realign (signified by the white column), so that the F2 comb’s pulses always overlap with those returning from the target and no information is lost.
Credit
B. Hayes / NIST
Usage Restrictions
No restrictions.
License
Public Domain