E1=a1*exp(-iwt)exp(-t/2*t1)(*first decay path*)
E1=a1*exp(-i(w+f)t)exp(-t/2*t2) (*second decay path*)
I=(E1+E2)(E1+E2)* (*interference fringes is because of interference of two decay fields*)
I=a1^2*exp(-t/t1)+a2^2*exp(-t/t2)+2a1a2*exp-(1/2*(t/t1+t/t2))*cos(ft)