Patent ID: 7170910

Claim:
A laser, comprising: at least a fiber having a guiding core and a shell cladding said guiding core, wherein said shell has an evanescent-field area; at least a first grating located at a first position of said guiding core, wherein said first position corresponds to said evanescent-field area; a second grating and a third grating located in front of and in rear of said first grating, respectively; and an optical gain medium having a dopant of rare-earth ions and attached to said evanescent-field area, wherein when a first pumping light beam passes through said second grating, said first pumping light beam is coupled into said optical gain medium by said first grating to excite said dopant of rare-earth ions for generating an optical gain; and a resonated light beam is generated and repeatedly reflected between said second grating and said third grating and an energy of said resonated light beam is repeatedly amplified thereby.