Giant terahertz polarization rotation in ultrathin films of aligned carbon nanotubes

• DOI: 10.1364/optica.422826
• Publication Date: 2021-04-19T11:02:46Z
• Authors: Andrey Baydin; Natsumi Komatsu; Fuyang Tay; Saunab Ghosh; Takuma Makihara; G. Timothy Noe; Junichiro Kono
• Keywords: FOS: Physical sciences; 02 engineering and technology; 0210 nano-technology; Physics - Optics; Optics (physics.optics)

For easy manipulation of polarization states of light for applications in communications, imaging, and information processing, an efficient mechanism is desired for rotating light polarization with a minimum interaction length. Here, we report giant polarization rotations for terahertz (THz) electromagnetic waves in ultrathin (

∼

45

n m

), high-density films of aligned carbon nanotubes. We observed polarization rotations of up to

∼

20 ∘

and

∼

110 ∘

for transmitted and reflected THz pulses, respectively. The amount of polarization rotation was a sensitive function of the angle between the incident THz polarization and the nanotube alignment direction, exhibiting a “magic” angle at which the total rotation through transmission and reflection becomes exactly 90°. Our model quantitatively explains these giant rotations as a result of extremely anisotropic optical constants, demonstrating that aligned carbon nanotubes promise ultrathin, broadband, and tunable THz polarization devices.