Dear CHANDRASENAN,
1. As it is said, to split a light into two counter-propagating light waves, one way is to use Sagnac loop with different configurations depending on the applications.
2. In Q2, if you mean practically how to set the polarization, you can use a Polaroid sheet, easily available in Market.
Please describe your work for more help.
Best wishes
Faramarz E. Seraji