How to calculate pulse energy?

[Jiho]

The pulse laser is converted by photo detector(PD) into electrical current. And we can see output voltage of photo detector by using oscilloscope.

Now we get voltage function detected by PD. Now I need to calculate energy of pulse. But I don't know how I do it.. Is there any formula I can use??

 

[BvU]

The pulse laser is converted

I should hope not !
You want to know an expression for the conversion of some voltage resulting from a laser pulse that hits a photodiode. So you need to calibrate your setup. Not so easy. You don't happen to have a power meter, I suppose ? So what do you know of your photodiode ?

 

[tech99]

The pulse laser is converted by photo detector(PD) into electrical current. And we can see output voltage of photo detector by using oscilloscope.

Now we get voltage function detected by PD. Now I need to calculate energy of pulse. But I don't know how I do it.. Is there any formula I can use??

I think the simple assumption is that the output voltage of the diode is proportional to optical power. Maybe you could then obtain a reference by using the light from a known source - not a standard candle (!) but maybe a known lamp. You would need to study the units of illumination to do this. Remember the laser has a parallel beam so it does not fall with distance (until many km).
The energy contained in the pulse will be its power x time.