THz wave emission from the Cu₂O/Cu interface under femtosecond laser irradiation

Cu or Cu/Au (80 nm thick Cu, 50 nm thick Au) sputtered on Si were kept at 25 °C for a week or annealed at a temperature from 80 to 300 °C, then tested for THz emission under femtosecond laser irradiation (35 fs-800 nm). THz radiation was detected from samples annealed from 80 to 170 °C, which had a Cu₂O/Cu interface as the THz source. Cu/Au/Si annealed at 80 °C emitted the highest THz radiation because of high laser absorption by the porous Cu₂O layer formed at low temperature and the Au film reflected THz radiation and/or increased the laser absorption by the Fabry-Pérot effect. (author)