All-fiber high-order mode laser using a metal-clad transverse mode filter

We propose and demonstrate an all-fiber laser with LP11 mode output. A transverse mode filter is designed and fabricated to suppress the fundamental mode and enable the fiber laser to oscillate in the second-order (LP11) transverse mode. The mechanism is to introduce relatively low ohmic loss for the TE01 mode and much higher ohmic losses for other modes through the loss of evanescent waves in the metal clad. The fiber laser operates at the center wavelength of 1053.9 nm with a narrow 3 dB linewidth of 0.019 nm. Four states of cylindrical vector mode with high modal purity are obtained through adjusting the intracavity polarization controller. This approach has great potentiality and scalability of realizing single high-order mode fiber laser, from which a wide range of applications could benefit. (C) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement