Research On Novel Rare-earth Doped Fiber Lasers

Since the first fiber laser appeared in the world, it has attracted broad focus and research for its unique advantages, followed by its rapid development. In recent years, with the development of optical communication, laser weapon, Distributed Fiber Raman Photon Temperature Sensor and space sensing with laser wavelength at the human eye's safe band, it has caused urgent demand for appropriate high-power light source. The research of this thesis concerns mostly high-power single-frequency and Q-switched fiber laser.The major results in the dissertation are obtained as the following:1. Use Fourier transform method to analyse the influence of modal amplitude and phase fluctuations in a mode-locked laser on performance of its output pulse. Results show that the pulse shape and the bandwidth remain essentially constant when the modes have amplitude and phase fluctuations, but appear superimposed on a fluctuations background. The phase variations will cause the fluctuation of peak. The physical picture in this paper is concise and is helpful to get stable mode-locked laser output in experiments.2. The invention of DFB self-injection ring cavity fiber laser is successfully made, in which DFB laser is used as the seed source to achieve self-injection and the SHB effect of erbium doped fiber taken to narrow the linewidth of light from the DFB fiber laser. Finally we gained a single-frequency fiber laser with power of 116mW and linewidth of less than 2kHz. The laser works very stably with the potential of further boosting the output power.3. The characteristics of the output of passively Q-switched fiber laser with erbium doped fiber as the saturable absorber is investigated. We have obtained Q-switched laser output with stable center wavelength which has peak power of more than 0.2W, pulse width of less than 4us and SNR of more than 80 dB by using the ring cavity configuration. This Q-switched fiber laser has several good qualities such as low cost, compact configuration and stable output.4. The characteristics of the output of gain switching ring cavity erbium doped fiber is investigated. We gained pulse width and repetition frequency tunable output with peak power of more than 0.3W and pulse width of less than 1us. We also carried out some research about the characteristics of the gain guiding of DFB fiber laser and gained the pulse output with pulse width of less than 200ns. This kind of fiber laser has huge potential in future application.5. Self-Q-switched fiber lasers with Rayleigh-SBS ring mirrors is investigated. Through adding polarizer and polarization controller to reduce the threshold of the laser, we gained pulse output with peak power of 200W-400W and pulse width of less than 20ns in the band of 1.5 um and 2ns in the band of 1um. We also did some research about the output characteristics of SBS passively mode-locked fiber laser in the band of 1.5um.The innovative results in this dissertation are as following:1. By using low-power DFB fiber laser as the seed source to induce spatial hole burning in erbium doped fiber and the ring cavity configuration to achieve self-injection, we gained narrow linewidth and high power single-frequency laser output with linewidth of less than 2kHz and power of more than 120mW.2. We investigated for the first time the output characteristics of DFB fiber laser under gain switching and the peak power of the pulse. We gained the pulse width of less than 200ns, the pulse power is far above the output power of the laser under stable conditions.3. Through adding polarizer and polarization controller in traditional RS-SBS passively Q-switched fiber laser to reduce the threshold of the laser, we gained Q-switched pulse output with pulse width of less than 12ns and power of 200W-400W under low pump level.