Study On The Novel Rare-earth Doped Fiber Amplifier

Ultrashort laser amplifiers have always been a very important field in laser research, especially those ultrashort laser amplifier based on rare-earth doped fiber, which has advantages with small size, compact structure, high pump efficiency, excellent heat dissipation and so on. In particular, erbium-doped fiber amplifiers in the 1.5 um with eye-safe feature, are widely used in scientific research such as high power producing, terahertz generation, precision spectroscopy controlling and so on. It also have found wide application in laser radar, laser ranging, remote sensing, environmental monitoring, high precision detection and medical equipment. In addition, with second harmonic generation, the output spectrum of high power ultrashort pulse erbium-doped fiber laser system can be extended to near 800 nm easily. With the help of available titanium sapphire laser system components, precise control of the laser output can be achieved.The major research works and results are as following:1. Base on a novel amplification technique-divided pulse amplification, we realized a high power Er-doped fiber laser. A novel configuration was designed for pulse division and recombination by using 45°-cut YVO4 crystal pairs. We verified the pulse-division process and acquired an amplified average power of 2 W. After compression of the amplified pulse with appropriate length of single-mode fiber, second harmonic generation from a PPLN crystal was achieved at 780 nm with the output power of 110 mW and pulse duration of 95.7 fs.2. Based on chirped pulse amplification technique, we designed an all-fiber ultrashort Er-doped fiber laser system. The oscillator was based on nonlinear polarization rotation. In order to structure an all-fiber laser system, we used dispersion compensation fiber to stretch the pulse and single mode fiber to compress the laser pulse the time domain, respectively. Spectra distortion was precisely controlled during the whole amplification process, which led to a laser output with 420fs pulse duration and 1.81 W average power. Then one piece of periodically poled lithium niobate crystal was employed to yield second-harmonic generation, so that the operating wavelength was extended to near infrared regime centered at 780 nm with llnm spectra bandwidth.