We demonstrate 1.54 W of laser emission at 905 nm from a fully fiber-based polarization-maintained master oscillator power amplifier (MOPA). The laser system comprises a directly modulated Fabry-Perot laser diode emitting at 905 nm, which is subsequently amplified by a three-stage pre-amplifier and a main amplifier. The system achieved an output energy of 0.15 mJ at a repetition frequency of 10 kHz with a pulse width of 20 ns.
Large mode field reverse polarization maintaining optical fiber coupler (LMFRPM-OFC) is the key optical fiber component of high power fiber laser, which plays an important role in the fields of high power polarized laser, etc. The polarization temperature dependence of LMFRPM-OFC means that reverse extinction ratio of polarized laser transmitted through the optical fiber coupler is affected by the temperature change. The temperature change will cause the birefringence and polarization state of the optical fiber coupler to change, thus affecting the stable transmission of polarized laser. Therefore, it is of great significance to study the polarization temperature characteristics of optical fiber couplers. In this paper, the polarization state of optical fiber coupler samples is tested. Test results: In the process of temperature change, the polarization state of the optical fiber coupler to change, and the change trend is opposite to the direction of temperature change. This phenomenon is due to the change of the structure in the stress zone in the LMFRPM-OFC caused by the temperature change, which affects the polarization state of the output high-power polarized lasers. In this paper, the polarization temperature dependence of LMFRPM-OFC is studied through active or passive cooling. The polarization temperature dependence of LMFRPM-OFC is effectively reduced through experiments of active cooling and passive cooling, and the reliability of polarization output of LMFRPM-OFC and high-power polarized lasers is improved.
We verify its advantage for fiber coupling through experiments base on large clad fiber, and which core/clad diameter is 196.5/788 μm. The coupling fiber with core/clad diameter of 200/220 μm was fused behind the large clad fiber, and which diameter of the fiber core is bigger than or equal to the diameter of the fiber core of the large clad fiber. The output laser power is 528 W at the incident power 600 W, and the corresponding fiber coupling efficiency is 88%.
Recently, narrow linewidth fiber lasers are widely applied in coherent detection and wavelength beam combining. In high-power linearly polarized narrow linewidth fiber lasers, the effect of mode instability (TMI) is one of the main factors limiting its power increase. In this paper, the influence of TMI effect on the output power of high-power linearly polarized narrow-linewidth fiber laser is analyzed, and the suppression method of TMI effect is proposed. Long-wave pumping technologies are used in this article. A single frequency laser with an output power of 100mW is used as the seed source. And the phase modulator broadens the linewidth of the seed source to 23GHz. After three stage amplification, the linewidth of 23GHz, power of 2.2kW, and center wavelength of 1064nm are finally realized. Linearly polarized narrow linewidth fiber laser output with extinction ratio of 98% is achieved. Beam quality is M2x=1.2 and M2y=1.21. The influence of the pump wavelength on the TMI effect is analyzed. Due to the small core diameter of the fiber (20μm), a high absorption coefficient of the gain fiber for the pump light (1.8dB/m@976nm), the core temperature is high. And the heat introduced by the pump photo quantum defect, causes the refractive index of the fiber core to change. Finally, the TMI effect occurs at lower power. When the pump wavelength is shifted to the long wavelength, the quantum defect of the pump light and the pump absorption coefficient are both reduced. The heat distribution on the entire length of the fiber or on the unit length is reduced. The TMI threshold is increased. And the output power of the linearly polarized narrow linewidth fiber laser is improved.
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