Anisotropic Optical Properties of Monolayer Aligned Single‐Walled Carbon Nanotubes

The 2D materials are the fundamental building blocks for modern optoelectronics and photonics. Optically anisotropic monolayers give even more flexibility in device design and performance. However, the random orientation of optical axes in the large‐scale samples prevents anisotropic monolayers from widespread use. The alternative structure is a monolayer of aligned single‐walled carbon nanotubes (SWCNTs) with an anisotropic dielectric tensor. Herein, aligned SWCNTs monolayer anisotropic optical constants in a broad spectral range (250–1700 nm) are measured for the first time. It is discovered that it has a large birefringence of Δ n ≈ 0.2 and a high dichroism of Δ k ≈ 0.4. Moreover, it is demonstrated that aligned SWCNTs monolayer optical response can be described by an effective medium approximation using the graphene dielectric function. In addition, it gives a universal approach for a determination of carbon concentration in nanotubes structures. It also applies for other types of carbon nanotubes, such as multi‐walled and randomly oriented carbon nanotubes arrays. Hence, in the results, aligned SWCNTs monolayer optical constants are added to the optical anisotropy database, which facilitates the longstanding challenge of using 1D structures in two dimensions, and a rapid characterization method for carbon nanotubes is provided.