Photonic Generation of Chirped Millimeter-Wave Pulses Based on Nonlinear Frequency-to-Time Mapping in a Nonlinearly Chirped Fiber Bragg Grating
Photonic Generation of Chirped Millimeter-Wave Pulses Based on Nonlinear Frequency-to-Time Mapping in a Nonlinearly Chirped Fiber Bragg Grating
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DOI：
10.1109/tmtt.2007.914639
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发表时间：
2008-02
影响因子：
4.3
通讯作者：
Chao Wang;J. Yao
中科院分区：
文献类型：
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作者：
Chao Wang;J. Yao
提出并通过实验证明了一种基于频谱整形和非线性频率到时间映射以光学方式生成具有可调谐啁啾速率的啁啾毫米波脉冲的新方法。在所提出的方法中，飞秒脉冲激光的超短脉冲的光功率谱由具有正弦频率响应的双抽头 Sagnac 环路滤波器整形。然后，频谱整形的光脉冲被发送到具有可调非线性群延迟的非线性啁啾光纤布拉格光栅（NL-CFBG），作为高阶色散器件来执行非线性频率到时间的映射。然后在高速光电探测器的输出处产生具有高中心频率和大啁啾率的啁啾电脉冲。所提出的系统中使用的NL-CFBG是由基于应变梯度光束调谐的规则线性啁啾光纤布拉格光栅产生的。对啁啾脉冲产生进行了详细的理论分析，并通过数值模拟和实验进行了验证。通过实验产生了中心频率约为 35 GHz、瞬时频率啁啾率为 0.053 和 0.074 GHz/ps 的毫米波脉冲。
A novel approach to optically generating chirped millimeter-wave pulses with tunable chirp rate based on spectral shaping and nonlinear frequency-to-time mapping is proposed and experimentally demonstrated. In the proposed approach, the optical power spectrum of an ultrashort pulse from a femtosecond pulsed laser is shaped by a two-tap Sagnac loop filter that has a sinusoidal frequency response. The spectrum-shaped optical pulse is then sent to a nonlinearly chirped fiber Bragg grating (NL-CFBG) with a tunable nonlinear group delay to serve as a high-order dispersive device to perform the nonlinear frequency-to-time mapping. A chirped electrical pulse with a high central frequency and large chirp rate is then generated at the output of a high-speed photodetector. The NL-CFBG used in the proposed system is produced from a regular linearly chirped fiber Bragg grating based on strain-gradient beam tuning. A detailed theoretical analysis on the chirped pulse generation is developed, which is verified by numerical simulations and experiments. Millimeter-wave pulses with a central frequency of around 35 GHz and instantaneous frequency chirp rates of 0.053 and 0.074 GHz/ps are experimentally generated.