Graphene-Coated Twisted Taper for Highly Sensitive Sensing and All-Optical Modulation

Abstract

An ultracompact graphene-coated twisted silica taper is fabricated and applied for highly sensitive sensing and all-optical modulation. The coated graphene is used as functional material with excellent optical properties, such as fast thermal response to enhance the temperature sensing and surface plasmon polariton (SPP) effect to produce and confine more propagating modes in the twisted taper. Therefore, the enhanced multimode interference further improves the optical sensitivities as used for temperature and strain sensings. High sensitivities of −127.2 pm/°C for temperature sensing and −173.9 pm/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \varepsilon $ </tex-math></inline-formula> for tensile strain sensing are observed in sequence, comparatively, along with those sensitivities of only −73.7 pm/°C and −163.5 pm/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \varepsilon $ </tex-math></inline-formula> for the twisted taper without coated graphene. Furthermore, all-optical modulation of the proposed taper is also investigated, showing a resonant wavelength shift of about 0.9 nm with a pump wavelength of 1470 nm and a power of 2.07 mW, while nearly no wavelength shift for the comparative case without coated graphene.