W. Happer has written:

'Light propagation and light shifts in optical pumping experiments'

This is kirit vaghela, The answer for the above question is that as far as ruby laser is concerned the pupmping is used is nothing but it is completed by optical pupmping.

He didn't.

Einstein simply developed the theoretical basis that made optical pumping a goal to seek, in order to create a lasing action.

Dieter Suter has written:

'The physics of laser-atom interactions' -- subject(s): Optical pumping, Laser manipulation (Nuclear physics), Laser spectroscopy