Electrical Generation of Polarized Broadband Radiation from an On-Chip Aligned Carbon Nanotube Film

Microsized light sources with polarized or broadband emission can be used for a variety of applications. However, the system directly generating polarized and broad-spectrum light without using polarizers has not been established. Here, we found that a nano-device of densely packed and highly aligned carbon nanotube (CNT) films on silicon chips can emit polarized light with a broad spectrum. We observed spatial emission patterns that are dependent on the angle between the electrical bias and the CNT alignment direction, which are caused not only by the large thermal conductivity anisotropy of the film but also by finite thermal conductance in the CNT-electrode contact. Utilizing the thermal and electrical anisotropy, strongly localized emission was achieved from a narrow (∼1 μm) strip of aligned CNTs connecting edges of two displaced electrodes. This device's unique ability to directly generate polarized ultrabroadband radiation may greatly expand the range of applications of microsized light sources.