Timing Improvements to Silicon Photomultiplier Transimpedance Amplifier Circuit
Don't share the -30V reference for both channels. Instead, duplicate R3 R4 C6 C7 for each channel, this will lower crosstalk.

If you want to measure the delay between both pulses, then both circuits should have identical delays. Since you're down into picoseconds, propagation delay in traces matters. Since FR-4 propagation time varies slightly with temperature, I'd advise having two absolutely identical layouts, with very short traces to the coax connectors.

This will need to be validated by feeding the same pulse of light via matched length fiber optics into the sensors, then checking the delay between recorded pulses. They should be identical. After this, swap the fibers and measure again. Or shine a very fast laser on both sensors simultaneously. Anyway, you get the idea: circuit performance must be validated.

I'm gonna disagree with analogsystemsrf on decoupling: since the inductance of the bondwires inside your opamp is higher than the inductance of a single, well-routed SMD cap, the number of decoupling caps doesn't matter. What matters is that the decoupling cap should be as close as possible to the chip. It should also be large enough to provide all the current needed during the event.

I'd put a 1µF 0805 cap as close as possible, then connect this to the main supply via a 1R resistor. The main supply should have a local cap, like 10µF MLCC.

If you hand solder it, you can stick the decoupling cap really close, closer than pick&amp;place clearances would allow. 

Use the SOT23 package, it will have lower inductance.


  What would be the best way to go about this, keeping the speed the same while increasing gain? 


You could use a faster opamp like LMH6629 OPA847 ADA4895 but of course these are even more finicky about layout.

Must-read links:

http://www.eetimes.com/document.asp?doc_id=1274887

http://mksa.dii.univpm.it/biblioteca/sala_tecnica/scaffale_dispositivi/instr_amp/AN-202.pdf