Dear Biswajit, homotopy methods have been applied to optimal control problems. You can refer to the software HAMPATH : http://cots.perso.enseeiht.fr/hampath/
The best referecne concerning homotopy is the book frol Allgower and Georg:
Any special reason why you want HAM ? there are some betterment also available. including OHAM etc. And why in FORTRAN ? Any particular reason here as well ?