Abstract
One of the problems still facing workers in the terahertz field, is to find suitable materials with a low refractive index and extinction, that can be used as filters or substrates. Here, we show results on THz-TDS measurements on polystyrene foam which demonstrate that this material has dielectric properties that make it very suitable for many THz applications. We have measured the frequency-dependent extinction and refractive index of three kinds of polystyrene foam: One produced with l-chloro-1, l-difluoroethane (also called HCFC 142b) as a blowing agent, and two with CO2 as the blowing agent. The experimental setup uses 15 fs pulses from a 72 MHz repetition- rate, Ti:Sapphire oscillator to generate THz pulses from a semi-large aperture SI-GaAs emitter. These are detected using electro-optic sampling in a 0.1 mm thick (110) oriented GaP crystal.1 We have studied three samples: Sample A (Styrodur 2500), is produced with HCFC 142 b as a blowing agent, whereas samples B (Styrodur 2500 C) and C (Styrodur 4000 CS) are blown with CO2. The samples differ mainly in their mass density, which is the highest for sample C. In Fig. 1 we plot an example of the measured THz waveforms obtained with and without polystyrene foam C in the focus of the THz beam.
© 2002 Optical Society of America
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