434 W all-fiber linear-polarization dual-frequency Yb-doped fiber laser carrying low-noise radio frequency signal

We demonstrate a high power dual-frequency linear-polarization fiber laser that carries radio frequency signal. Such fiber laser is based on an all-fiber master oscillator power amplifier configuration that consists of a dual-frequency seed laser and three-stage amplifiers. The dual-frequency seed laser is constructed by recombining two beams that are split from a single-frequency linearly-polarized laser. One beam has initial frequency and the other beam is modulated by an acoustic-optical modulator to have a frequency shift of 150 MHz. Then the radio frequency signal of 150 MHz is carried on the laser due to the beat frequency of these two beams. In the main amplifier, a piece of polarization maintaining large-mode-area fiber with short length is used to combine the SBS suppression with high power amplification. As a result, the dual-frequency laser is amplified to 434 W without the occurrence of SBS. The slope efficiency is 81.3%. The polarization degree of the laser and the modulation depth of the optically carried radio frequency signal are both well maintained during the amplification process. Besides, a high signal-noise-ratio of above 75 dB is realized, which demonstrates the low-noise property of the optically carried radio frequency signal. To the best of our knowledge, this is the highest reported output power of the optically carried radio frequency signal.