Patent ID: 6690685
Filing Date: 2004-02-10
Classification: G02B,H01S

Abstract:
Method for writing grating for a fiber laser, the method comprising the following steps:providing a length of optically active fiber having a rare-earth-doped core photosensitized in a first region and a second region for defining the length of the optically active fiber having a reflecting surface in the second region and having the first region for preparing a first grating, said reflecting surface having a second reflection wavelength band wider than a first reflection wavelength band expected for the first grating; controlling a power level of pump radiation power by scanning the power of the pump radiation in a predetermined power range by a processor; optically pumping the length of the optically active fiber at the power level scanned to excite the rare-earth-doped core to provide an amplified stimulated emission through the first or second region as a free-running emission; writing the first grating in the first region, in order to allow the amplified stimulated emission to travel forward and backward between the first grating and the reflecting surface and to consequently induce a laser emission from the optically active fiber by captivating the free-running emission; measuring, during the step of writing the first grating, the optical power of the laser emission at the power level scanned; determining by the processor a ratio of the optical power of the laser emission divided by the power level scanned in order to obtain a current value of the laser efficiency; comparing the current value of the laser efficiency at a current scan increment to a preceding value of the laser efficiency at a previous scan increment; returning to the power level step to increase the power level of pump radiation power by a new current scan increment when the current value is less than the preceding value of the laser efficiency; controlling by the processor the step of writing the first grating according to the measured optical power such that when the current value is greater than the preceding value of the laser efficiency for reaching a limit value, stopping the step of writing the first grating.