When using the AD8015 connected AC coupled to an APD - like Fig. 17 at the data sheet.
I illuminate it with a laser pulse of 50ns pulse width. I am getting an output of only ~10ns width( on 50ohm scope input).
The AC input cap is 0.1uF, The AC output caps are also 0.1uF.
The chip is biased with +/-5V.