Probing degrees of orientation of polar molecules with harmonic emission in ultrashort laser pulses

The orientation of molecules with respect to the laser polarization brings rich physics into laser-molecule interaction. However, the degree of orientation of a polar molecule is difficult to measure in present experiments. Here, through numerical solution of the time-dependent Schrödinger equation, we show that high-order-harmonic generation from polar molecules with a large permanent dipole in ultrashort laser pulses can be used as a sensitive tool to probe the degree of orientation. The underlying mechanism is discussed.