High-order modes micro-knot excited by a long-period fiber grating

We developed novel fiber microknots which are designed for high order mode beams traveling in the fiber. The device is based on long period fiber gratings which excite high order modes in tapered fiber and a microknot which is fabricated on the tapered fiber. Thus, the light that resonates in the microknot is propagating in the tapered fiber in high order modes which have higher coupling to the environment. The light which exits the microknot and continue to propagate in the fiber is then exited back to the Gaussian mode by another long period fiber grating before the fiber returns to be a single mode fiber. We found that the spectral response of these microknots have deeper resonances and improved Q-factor.