Patent attributes
A method and apparatus use a photonic-crystal fiber having a very large core while maintaining a single transverse mode. In some embodiments, the method and apparatus includes a photonic-crystal fiber or rod (PCF or PCR) optical device having a beam-expanding endcap formed, e.g., by collapsing or otherwise sealing holes of the PCF or PCR. In some fiber lasers and amplifiers having large cores problems exist related to energy being generated at multiple-modes (i.e., polygamy), and of mode hopping (i.e., promiscuity) due to limited control of energy levels and fluctuations. The problems of multiple-modes and mode hopping result from the use of large-diameter waveguides, and are addressed by the invention. This is especially true in lasers using large amounts of energy (i.e., lasers in the one-megawatt or more range).
