Highly polarization-sensitive far infrared detector based on optical antenna integrated aligned carbon nanotube film
Polarization detection provides another important characterization of light field beyond intensity and spectrum. It is desired for high-fidelity information acquisition and high-precision target recognition in the infrared detection regime. Single-wall carbon nanotube (SWCNT) films have been investigated for infrared detection with considerable sensitivity at room temperature based on photothermoelectric effect. In this work, a bowtie antenna integrated aligned SWCNT film is proposed for highly polarization-sensitive far infrared detection. The SWCNT film is shaped into a belt and diversely doped to form a p-n junction at the center. The SWCNTs are arranged perpendicular to the electronic transportation direction. The antenna is aligned at the junction and along the SWCNTs. Based on the following four factors: 1) deep-subwavelength light concentration at the junction, 2) alignment between the SWCNTs and the antenna, 3) anisotropic heat transfer in the aligned SWCNT film, 4) light field reduction within the gap of the bowtie antenna for the polarization perpendicular to the antenna axis, the ratio between the responsivities for the polarizations parallel and perpendicular to the SWCNTs could be higher than 13600. By changing the size of the antenna, the resonant frequency could be tuned. Over the range from 0.5 to 1.5 THz, the peak polarization extinction ratios at different resonant frequencies are all bigger than 700, and they are 16 to 320 times higher than that of the aligned SWCNT belt without the antenna. Moreover, the integration of the antenna and the aligned SWCNT belt also enhances the responsivity by 1 to 2 orders of magnitude. Compared to an aligned multi-wall carbon nanotube film, an aligned SWCNT film integrated with an optical antenna is more favorable for highly polarization sensitive far infrared detection. The result is based on the numerical simulations of the light and the thermal fields.