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Different characteristic surface structures such as capsules, regularly spaced droplets, and fibers are formed by electrostatic interaction between poly-L-lysine (PLL) and gellan gum via polyion complex (PIC) formation. Spherical droplet PIC capsules of varying diameters form in solutions. Some dyes adsorb on the surface of the capsules, and other dyes penetrate into the capsules. The strong PIC fiber can be spinnable by gravity and by wet spinning in ethanol. This fiber possesses a counterion pairing structure and exhibits the nervation/veining pattern and hollow yarn. The tensile strength of the fiber is 27.8 kg/mm 2 [1.40 g/denier (d)] and the knotting strength is 9.98 kg/mm 2 (1.13 g/d). By using an organic crosslinking agent, epichlorohydrin, the tensile strength can be increased to 38.5 kg/mm 2 (2.46 g/d) and the knotting strength can be increased to 12.2 kg/mm 2 (1.99 g/d). The PIC fiber can be dyed by five different dyeing procedures such as direct and vat dyeings. The PLL PIC fiber is water insoluble and has potential as a new synthetic polypeptide fiber technology.

SUMMARY Different characteristic surface structures such as true and hemi spheres, honeycomb, regularly spaced droplets and fibers are created by electrostatic polysaccharide interaction between chitosan and gellan gum via polyion complex formation. Spherical droplet capsules of varying diameters form in solution. Strong fibers can be spun by gravity and by wet spinning in ethanol. These fibers possess a counter ion pairing structure, and exhibit a 'nervatiodveining' pattern.

An ultralow-repetition-rate, all-polarization-maintaining (PM), Er-doped, ultrashort-pulse fiber laser was demonstrated using a single-wall-carbon-nanotube polyimide film. Using a ring cavity configuration, output pulses with pulse energy of 0.7-2.6 nJ were obtained at an ultralow repetition rate of 943-154 kHz for a fiber length of 0.1-1.3 km. A novel θ (theta) cavity configuration was proposed, which enabled us to reduce the required fiber length by half. A repetition rate of 132 kHz was achieved using this configuration with 909 m of PM fiber.