A fiber-integrated ultrabroadband optical power sensor based on multi-walled carbon nanotubes and U-shaped fiber with bandwidth ranging from 405 nm to 7.767 μm

The ultrabroadband photodetectors are considered to hold significant potential for applications in optical sensing and communication. In this study, we report an ultrabroadband fiber-integrated optical power sensor (FOPS) based on the photothermal effect of multi-walled carbon nanotubes (MWCNTs). The device consists of two main components: the U-shaped fiber (UF) and the photosensitive unit (PSU), wherein the PSU is comprised of polydimethylsiloxane (PDMS) doped with MWCNTs. Under illumination, the photothermal effect of MWCNTs causes a thermal expansion of the PDMS, resulting in compression deformation of UF and transmission spectrum blueshift. Experimental results demonstrate that the proposed device achieves an optical photodetection ranging from 405 nm to 7.767 μm with a responsivity of 0.484 nm/mW. The response time exhibits a rising edge of 13 s and a falling edge of 7 s. Additionally, the device has integrated light motion tracking capability, achieving a displacement resolution of incident light as 1.25 nm/mm. As the proposed FOPS has advantages of ultrabroad detection band and high responsivity, it is a promising design for light detection.