Keywords:nonlinear fiber optics, Optically induced long period fiber grating
We demonstrate here efficient all optical mode conversion in standard single-mode fiber via transient long period fiber grating (LPG) induced by sub-nanosecond laser pulses through the optical Kerr effect. Pump is launched well below the cut-off region of the fiber where the fiber can only supports LP01 and LP11 spatial modes. The beating of the two guided modes induce refractive index grating exploiting the Kerr effect. Probe beam is co-propagating with the pump at the same wavelength but with different polarization, exhibiting efficient mode conversion efficiency. The launching of pump and probe beam at same wavelength makes the system inherently phase-matched which has increased the conversion efficiency. Maximum mode conversion achieved at very low pump peak power. The transient nature of the grating makes our approach unique from the existing results, making it suitable for several nonlinear and sensing applications.