Full text loading...
Experimental setup: The THz spectrum is spatially resolved and focused onto a partly illuminated silicon wafer. The light induced absorption in the semiconductor enables to the frequency selective modulation of the THz spectrum. For clarity, only two exemplary THz frequencies are shown in this illustration.
The upper curve (black) shows the spectrum of the transmitted THz radiation. Both the first and the second order of diffraction are transmitted. The lower curve (red) shows THz radiation modulated at 420 GHz by the illumination of a small spot on the semiconductor. The upper curve is shifted by 60 dB.
Transfer function of the system for two different notch filters with center frequencies of 340 and 420 GHz, respectively. Inset: the frequency-to-space mapping, the x- and y-error bars indicate the FWHMs of the frequency distribution and the spot size for single frequencies, respectively.
The measured transfer functions of a double (lower curve) and triple (upper curve) notch filter. Those arbitrary filters can be obtained by applying custom illumination pattern on to the silicon wafer. The upper curve is shifted by 10 dB for better visibility.
More than eight distinguishable frequencies can be switched on and off independently and allow encoding one byte of information into the THz signal.
Article metrics loading...