Controlling THz wave transmission through organic copper phthalocyanine (CuPc) films on Si by optical excitation

We show that transmission of THz waves through an organic copper phthalocyanine (CuPc) film on a Si wafer can be controlled by optical excitation. The carriers excited in silicon are injected into a CuPc film and transport along well-ordered direction of a CuPc film, resulting in making a CuPc film metallic and decreasing the THz transmission. Modulation efficiency depends on the phases of CuPc films. CuPc film/Si layers can be exploited for THz optical modulators.