Method for separating linear and circular photogalvanic effects an its application to ferroelectric lead germanate

A new method for separating linear and circular parts in the photogalvanic effect is proposed. This method utilizes an optical phase plate which is inserted between a sample and a phase-modulator crystal. We successfully applied the method to determine the linear photogalvanic coefficient β 36 and circular coefficient γ 33 of Bi 12 SiO 20 and γ 33 of Pb 5 Ge 3 O 11 . In particular, the change of the sign of γ 33 of Pb 5 Ge 3 O 11 was observed by reversing the spontaneous polarization. This phenomenon originates from the fact that the ferroelectric 180° domains of Pb 5 Ge 3 O 11 are related by mirror symmetry.