A liquid-crystalline polymer (LCP) containing an azotolane group in the mesogenic moeity has been synthesized (see Figure). A homogeneously aligned film of the LCP exhibits an extremely larp-e birefringence in a wide wavelength range. Upon irradiation by a pump laser beam, a large change in birefringence is quickly induced as a result of destruction of the homogeneous alignment of the azotolane moieties.