Photonic analog to digital converter using ultrafast photoconductors

There are many difficulties associated with such high sampling rates. One difficulty is in making sure that the sampling window is sufficiently precise in time, independent of the signal level or of other factors. Optical solutions may be able to improve this sampling precision. Our approach to this problem is to use photoconductive gates to sample electrical signals on a picosecond timescale. Achieving precisely timed delivery of optical pulses to trigger the sampling gates is expected to be relatively straightforward with optics without substantial degradation of the short pulse shape or variation in its arrival time. We are using low-temperature-grown GaAs photoconductive switches integrated with very small capacitors.