Highly sensitive all-optical control of light in WS2 coated microfiber knot resonator.

All-optical light-control-light functionality is realized in a layered tungsten disulfide (WS2) nanosheet coated microfiber knot resonator (MKR) structure. Mainly due to the photon generated excitons induced refractive index variation in WS2 nanosheets, a large variation in the transmitted power (∆T) can be observed under external violet/red laser excitation. The ∆T variation rates can reach up to ~0.4 dB/mW under violet pump light excitation whereas the state of the art light-control-light structures usually has a variation rate of less than 0.25 dB/mW. In terms of the response time, the averaged rise/fall time is ~0.12/0.1 s. The demonstrated structure has the advantages of easy fabrication, low cost and high sensitivity, therefore, it might be a promising candidate for building future all-fiber-optics based functional devices and all-optical circuitry.