I am looking for mathematical description of the method that I could implement, but if there is a program that already do this job it would be very helpful.
Unless you have a specific reason for finite element, you may also consider using the finite-difference method to obtain your vector solution. If you want to see what this might be light, take a look at Lectures 10-12 here:
http://emlab.utep.edu/ee5390cem.htm
I have since improved the description of the finite-difference method. See Topics 6b, 6c, and 7 here:
http://emlab.utep.edu/ee4386_5301_CompMethEE.htm
Both of the above courses have lecture notes and video recordings of the lectures.