  We show that helical turbulence produced during a first-order phase
transition generates circularly polarized cosmological gravitational waves
(GWs). The characteristic frequency of these GWs for an extreme case of the
phase transition model is around $10^{-3}$ --- $10^{-2}$ Hz with an energy
density parameter as high as $10^{-12}$ --- $10^{-11}$. The possibility of
detection is briefly discussed.
