Wu Rui, Torres-Company Victor, Leaird Daniel E, Weiner Andrew M
School of Electrical and Computer Engineering, Purdue University, 465 Northwestern Avenue, West Lafayette, Indiana 47907, USA.
Opt Express. 2013 Mar 11;21(5):6045-52. doi: 10.1364/OE.21.006045.
The generation of high-repetition-rate optical frequency combs with an ultra-broad, coherent and smooth spectrum is important for many applications in optical communications, radio-frequency photonics and optical arbitrary waveform generation. Usually, nonlinear broadening techniques of comb-based sources do not provide the required flatness over the whole available bandwidth. Here we present a 10-GHz ultra-broadband flat-topped optical frequency comb (> 3.64-THz or 28 nm bandwidth with ~365 spectral lines within 3.5-dB power variation) covering the entire C-band. The key enabling point is the development of a pre-shaping-free directly generated Gaussian comb-based 10-GHz pulse train to seed a highly nonlinear fiber with normal dispersion profile. The combination of the temporal characteristics of the seed pulses with the nonlinear device allows the pulses to enter into the optical wave-breaking regime, thus achieving a smooth flat-topped comb spectral envelope. To further illustrate the high spectral coherence of the comb, we demonstrate high-quality pedestal-free short pulse compression to the transform-limited duration.
产生具有超宽、相干且平滑光谱的高重复率光学频率梳对于光通信、射频光子学和光学任意波形产生中的许多应用而言至关重要。通常，基于频率梳的光源的非线性展宽技术无法在整个可用带宽上提供所需的平坦度。在此，我们展示了一种覆盖整个C波段的10吉赫兹超宽带平顶光学频率梳（带宽大于3.64太赫兹或28纳米，在3.5分贝功率变化范围内有~365条谱线）。关键的促成因素是开发了一种无需预整形直接产生的基于高斯频率梳的10吉赫兹脉冲序列，用于泵浦具有正色散分布的高非线性光纤。种子脉冲的时间特性与非线性器件的结合使得脉冲进入光学波破碎区域，从而实现平滑的平顶梳状光谱包络。为了进一步说明频率梳的高光谱相干性，我们展示了高质量的无基座短脉冲压缩至变换极限持续时间。
