Terahertz Polarization Properties of Free-Standing Millimeter-Scale Carbon Nanotube Array Sheets Cut With Femtosecond Laser Pulses

Vertically-aligned millimeter-scale multiwall carbon nanotube arrays (CNTAs) grown by catalytic chemical vapour deposition were cut by femtosecond laser pulses into thin free-standing sheets of aligned carbon nanotubes. Terahertz (THz) time-domain spectroscopy was used to measure the polarization dependence of the transmittance of the CNTA sheets from 0.5-2.2 THz. CNTA sheets with thicknesses of 40 μm and 150 μm showed high extinction ratios at 1 THz of 25 dB and dB, respectively. Furthermore, the transmittance of the 40 μm CNTA sheet for THz polarization parallel to the carbon nanotubes decreased with increasing frequency, resulting in an extinction ratio of 34 dB at 2 THz exceeding that of a commercial wire-grid polarizer. The potential of laser-cut free-standing CNTA sheets as terahertz polarizers is discussed.