信号光的调制对基于光纤光参量放大光脉冲源的改善

The improvement of fiber parametric amplifier pulse source via modulation of signal light

在理论上从四波混频的强度耦合方程出发,给出了基于光纤光参量放大(FOPA)光脉冲的光场表达式,并进一步分析了信号光被相位调制或强度调制后,光脉冲的频率啁啾和强度演化.结论指出:若信号光被强度调制,对所生成脉冲宽度无明显的影响,但可以提高消光比;若信号光被相位调制,所生成的脉冲具有更大的线性正啁啾,可以在相同的抽运功率条件下得到比无相位调制时更窄的脉冲.实验上给出了10GHz工作速率下的结果,其结果与理论分析符合得很好.通过信号光的相位调制,在0.5W平均抽运功率条件下得到了消光比22dB,脉宽为5.2ps的变换极限脉冲,与无调制情况相比脉宽减小了2ps.

Starting from the four-wave maxing coupled equations, we obtain the optical field expression of a fiber optical parametric amplifier （FOPA） pulse source. Furthermore, we analyze the evolvement of pulse frequency chirp and amplitude when the signal light is phase or intensity modulated. It is concluded that the pulse width has no significant improvement but the extinction ratio is improved when the signal light is intensity modulated; however, when the signal light is phase modulated, the pulse has enhanced positive linear frequency chirp, which means that we may obtain shorter pulse than that of the FOPA based pulse source which has the same pump power but without phase modulation on signal light. Finally, the experimental results of 10 GHz operation demonstrated the validity of our theoretical analysis. Using the FOPA pulse source with 0.5 W average pump power and phase modulated signal light, the transform limited pulse is obtained which has 22 dB extinction ratio and 5.2 ps pulse width, which is 2 ps narrower than that without modulation.