Millimeter-wave, terahertz, and mid-infrared transmissionthrough common clothing

This letter reports electromagnetic transmission measurements through cloth samples from eight types of fabrics common in garments and baggage. The transmission at millimeter-wave and terahertz frequencies was measured with a custom ErAs:GaAs tunable photomixing spectrometer. The IR transmission between 3 and $8\mu \mathrm{m}$ was measured with a Fourier-transform infrared spectrometer. All samples were usefully transparent at millimeter-wave frequencies (up to $300\mathrm{GHz}$ ) based on a $3\mathrm{dB}$ criterion, but became progressively opaque at higher frequencies in a highly sample-dependent manner. This is explained by the samples becoming “optically dense” in the THz region, so that the transmission becomes exponentially dependent on sample thickness. The attenuation in the IR region is very high $(⩾25\mathrm{dB})$ except in two samples (rayon and nylon), whose exceptional transparency (e.g., $-12\mathrm{dB}$ in nylon) is attributed to pores intrinsic to the material.