In the excellent book “His master’s voice” by Stanisław Lem mankind receives a message from an extraterrestrial intelligence which is transmitted with a neutrino laser. Would the construction of such a NASER (neutrino amplification by stimulated emission of radiation) be in principle possible or would it violate a fundamental theoretical principle?

The central physical concept for lasers is induced emission, where you get a second photon from de-exciting an atom of the optical medium with the same properties as the first: All difficulties from nuclear physics aside, because neutrinos are fermions, they would not occupy the same states due to the antisymmetry requirement of the wave function after a neutrino emission has been induced. So the answer is no!