Reading a photodiode in nanosecond intervals
1 ns ? no not possible or even close. 

You can turn it on in 30 ns but off takes longer with high impedance conventional switch, perhaps turn off &lt; 500ns with a shunt driver.

But to detect the light with this speed an extremely low capacitance  photo detector with very low impedance low gain amplifier because the current source slew rates slows down with lower light.  A GaP PD has a slew ON/OFF time of 1 ns / 140 ns  e.g. Thorlabs FGAP71 

You might need to get into lasers and advanced photonics for these decay times with fused silica photo detectors 1ns/1ns e.g. FDS010  ~$60 and then expensive amplifiers with microwave rugged assemblies for stability.

https://www.thorlabs.com/_sd.cfm?fileName=0636-S01.pdf&amp;partNumber=FDS010