10:45 〜 11:00
▼ [15a-2E-5] Terahertz emission from silver nano-metal ink
キーワード：nano metal ink,terahertz generation
Nano-metal ink serves as a powerful tool to make terahertz metamaterials by using a superfine inkjet printing system. On the other hand, since it consists of metal nanoparticles, the ink itself has structures with a nanometer scale. It has recently reported that, when such metal nanostructures are irradiated by femtosecond laser pulses, the surface plasmon is excited and the resulting local field enhancement produces terahertz emission. In this work, we study the emission of terahertz pulses from the surface coated by the nano-metal ink.
As a sample, we used the silver nano-metal ink (ULVAC, Ag1TeH) coated on a fused-silica substrate. In this ink, the silver nanoparticles covered with surfactants are dispersed. When the ink is baked, the surfactants are resolved and the nanoparticles get sintered. The baked silver nano-metal ink was pumped by a regeneratively amplified femtosecond laser pulses (Spectra-Physics, Solstice; 800 nm center wavelength, 50 fs pulse duration, 1 kHz repetition rate) at an angle of incidence of 45 degrees. The diameter of the pump light on the sample was about 4 mm. The terahertz pulses emitted from the sample surface were focused on a (110) ZnTe crystal with a thickness of 1 mm for electro-optical sampling. A piece of polystyrene foam and a black polyethylene filter were used to remove the pump light from the terahertz signal. A pair of wiregrid polarizers was used for measuring polarization of the signal.
We measured the terahertz waveforms emitted by irradiating the sample both with the p-polarized and s-polarized pump pulses. The intensity of the pump pulse was about 60 GW per square centimeter. The generated terahertz waves are p-polarized, which is irrespective of the polarization of the pump pulses. The p-polarized pump pulses generate larger terahertz signal than the s-polarized pump pulses. In our sample, nanostructures of the ink-coated surface produced during the sintering process can support the localized plasmon resonances. The terahertz emission from silver nano-metal ink can be explained by the following mechanism: The field of the pump pulse excites plasmon oscillation in the metal nanostructure and the enhanced electric field induces optical rectification through the broken symmetry perpendicular to the sample surface. This study will lead to future development of a unique metamaterial which itself emits terahertz waves.
As a sample, we used the silver nano-metal ink (ULVAC, Ag1TeH) coated on a fused-silica substrate. In this ink, the silver nanoparticles covered with surfactants are dispersed. When the ink is baked, the surfactants are resolved and the nanoparticles get sintered. The baked silver nano-metal ink was pumped by a regeneratively amplified femtosecond laser pulses (Spectra-Physics, Solstice; 800 nm center wavelength, 50 fs pulse duration, 1 kHz repetition rate) at an angle of incidence of 45 degrees. The diameter of the pump light on the sample was about 4 mm. The terahertz pulses emitted from the sample surface were focused on a (110) ZnTe crystal with a thickness of 1 mm for electro-optical sampling. A piece of polystyrene foam and a black polyethylene filter were used to remove the pump light from the terahertz signal. A pair of wiregrid polarizers was used for measuring polarization of the signal.
We measured the terahertz waveforms emitted by irradiating the sample both with the p-polarized and s-polarized pump pulses. The intensity of the pump pulse was about 60 GW per square centimeter. The generated terahertz waves are p-polarized, which is irrespective of the polarization of the pump pulses. The p-polarized pump pulses generate larger terahertz signal than the s-polarized pump pulses. In our sample, nanostructures of the ink-coated surface produced during the sintering process can support the localized plasmon resonances. The terahertz emission from silver nano-metal ink can be explained by the following mechanism: The field of the pump pulse excites plasmon oscillation in the metal nanostructure and the enhanced electric field induces optical rectification through the broken symmetry perpendicular to the sample surface. This study will lead to future development of a unique metamaterial which itself emits terahertz waves.