They can support kilowatt levels of continuous output power because of the fiber's high surface area to volume ratio, which allows efficient cooling.They may also be designed for single longitudinal mode operation of ultra-narrow distributed feedback lasers (DFB) where a phase-shifted Bragg grating overlaps the gain medium.It should provide sufficient cladding to confine the core and optical pump section over a relatively short piece of the fiber.State of the art high-power fiber laser technologies using rod-type amplifiers have reached 1 kW with 260 fs pulses [15] and made outstanding progress and delivered practical solutions for the most of these problems.However, the shortcoming of amplification systems with LPF is their relatively long (up to 1.2 m) unbendable rod-type fibers meaning a rather bulky and cumbersome optical scheme.[21] LPF fabrication is highly complex requiring significant processing such as precision drilling of the fiber pre-forms.For example, saturation fluence can be controlled by varying the reflectivity of the top reflector while modulation depth and recovery time can be tailored by changing the low temperature growing conditions for the absorber layers.This freedom of design has further extended the application of SESAMs into modelocking of fiber lasers where a relatively high modulation depth is needed to ensure self-starting and operation stability.[32][33][34][35] Applications of fiber lasers include material processing, telecommunications, spectroscopy, medicine, and directed energy weapons.