Abstract
An optically pumped ultrasensitive broadband terahertz (THz) wave modulator based on polyvinyl alcohol (PVA) film on Si wafer was demonstrated in this work. The THz time domain spectroscopy experiments confirm that the PVA/Si can drastically enhance the photo-induced THz wave modulation on the Si surface, especially when the PVA film is heated by a high-power laser. A modulation depth of 72% can be achieved only under 0.55 W/cm2 modulated laser power, which is superior significantly to the bare Si. The numerical simulations indicate that the laser processed PVA (LP-PVA) film increases the photo-generated carrier concentration on the Si surface in two orders of magnitude higher than that of bare Si. Moreover, the modulation mechanism and the dynamic process of laser heating on the PVA/Si have been discussed. This highly efficient THz modulation mechanism and its simple fabrication method have great application potentials in THz modulators.
Highlights
Terahertz (THz) science and technology have been developed rapidly over the past decade due to its superiority in security, communication, and spectroscopy[1,2,3]
We show an optically pumped ultrasensitive broadband THz wave modulator based on a simple non-doped organic polymer polyvinyl alcohol (PVA) film on Si wafer
The PVA/Si sample was prepared following the steps in Method, and the thickness of PVA film was 4.5μm accurately measured by a profilometer[33]
Summary
Terahertz (THz) science and technology have been developed rapidly over the past decade due to its superiority in security, communication, and spectroscopy[1,2,3]. The transmission of bare Si declines linearly with the increase of pump power, and PVA/Si without laser heating is similar to bare Si initially.
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