Study On Terahertz Devices Based On Tunable Brewster Angle Effect

Terahertz wave has become a hot research topic in recent years,showing great application prospects in terahertz communication,radar detection,astrophysics.As a typical phase change material,vanadium dioxide is widely used in terahertz tunable devices due to the wide range of conductivity change during the phase change.In this paper,based on the research of tunable Brewster angle of vanadium dioxide,a state switchable grating device is designed and manufactured.The specific contents are as follows:I.The properties of tunable Brewster angle of vanadium dioxide thin films were studied.The conductivity of vanadium dioxide film increases with the increase of tem perature and the change of reflectivity.When the incident light is p-polarized,the reflection is zero at the Brewster Angle and the phase difference is 180° before and after passing the Brewster Angle.The terahertz time-domain spectroscopy system was us ed to test the results.The results show that the used vanadium dioxide film can achieve 15° Brewster angle modulation under temperature control,and the amplitude modulation depth of the terahertz wave is 99.2%,and the phase modulation is close to 180°.II.A switchable terahertz reflective grating device is designed.Based on the tunable Brewster angle of vanadium dioxide,a vanadium dioxide grating device was fabricated by micro-nano machining.At different heating temperatures,the device can be displayed in three different working states: plane mirror,rainbow reflector and metal grating.Because the device has broadband beam control characteristics,we have also explored the application of this device in the field of terahertz nondestructive testing.III.The photoinduced phase transition properties of vanadium dioxide thin films were studied.A continuous wave semiconductor laser was used to pump the vanadium dioxide thin film.The terahertz transmission spectra were measured in the terahertz time domain spectroscopy system.The terahertz transmission spectra were studied under different power of pump light irradiation.Finally,the reconfigurable grating was tested with a digital micromirror device (DMD).