How Much charge is generated by laser pulse?
The DAC setting varies from laser to laser, so absolute charge as a function of DAC setting for red/infra-red/blue laser is not possible. This is particularly true for different iris settings and use of filters, where such calibration is almost impossible without so called beam-monitoring system. As a rule of thumb the signal integral-charge collected in the sensor of around ~2000 mV ns (on 50 Ohm input - i.e. 300 mV signal of 6-7 ns duration) corresponds to roughly ~1M e-h pairs or ~30 MIPs in 300 um thick non-irradiated silicon detector. The development of so called plasma effect/space charge screening can become an issue for red laser where the penetration depth is small and corresponding density of non-equilibrium carriers very high.
It is difficult to achive/reach plasma setting with IR where carriers are generated with lower density. In order to make an absolute charge measurement one needs to know the intensity of light when it leaves the optical system (so called in-beam monitoring system which utilizes semi-reflective mirror and photodiode). Usually this is done in such a way that the signal from alpha source is compared to the signal from the laser pulse and the signal from the laser to the output from the in-beam-monitoring photo diode.