Linewidth Controlled 50-W Output Polarization Maintaining Fiber Laser

Optical fiber amplification technology, which had made vast progress in Erbium doped fiber amplifiers (EDFAs) for communication applications, has recently increased dramatically the optical output at the 1.0-μm wavelength by means of cladding pumping techniques, in which pumping light is guided into the cladding of pumping fiber 1)~4). In the single-mode fiber lasers, owing to the core and clad configuration, any lightwave other than that of core guided modes in the employed fiber is difficult to be transmitted, so that the output light forms stable transverse modes in accordance with the index profile. This constitutes a major advantage when the output power of a fiber laser is used in combination with an external wavelength converter. However, when application to wavelength conversion is assumed, the wavelength stability, linewidth and polarization state of light source must be taken into consideration in the design, and this presents an important aspect different from using the fundamental laser wavelength directly. In this paper, the basic operation of fiber laser will be presented together with the design of a fiber laser with wavelength, linewidth and polarization state control for use in wavelength conversion application, and output performance up to 50 W of a fiber laser. 2. BASIC CONFIGURATION