Broadband electro-optic frequency comb generation in a lithium niobate microring resonator
Broadband electro-optic frequency comb generation in a lithium niobate microring resonator
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DOI：
10.1038/s41586-019-1008-7
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发表时间：
2019-04-18
期刊：
影响因子：
64.8
通讯作者：
Loncar, Marko
中科院分区：
文献类型：
--
作者：
Zhang, Mian;Buscaino, Brandon;Loncar, Marko
光学频率梳由等间距的离散光学频率组件组成，是光通信、精密计量、计时和光谱分析的基本工具(1-9)。目前，宽带梳子通常是由锁模激光器(10)或具有三阶克尔非线性的色散工程腔(11)产生的。另一种梳子生产方法在具有强二阶非线性的谐振器中使用电光(EO)相位调制，从而产生具有极好的稳定性和可控性的梳子(12-14)。然而，以前的电光梳子由于电光相互作用强度弱以及在自由空间系统中缺乏色散工程而被限制在较窄的宽度。在这里，我们通过在薄膜铌酸锂光子平台中实现集成的电光梳状发生器来克服这些限制，该平台具有大的电光响应、超低的光学损耗和高度共焦的微波场和光场(15)，同时实现了色散工程。我们测量的EO梳子跨越的频率比整个电信L频段(900多条梳线间隔约10千兆赫)还要多，我们展示了未来的色散工程可以实现八度跨度的梳子。此外，我们展示了我们的梳状发生器对调制频率失谐的高容忍度，频率间隔可在七个数量级(10赫兹到100兆赫)内精细控制，并利用这一特性在单个谐振器中产生双频梳状。我们的结果表明，集成电光梳状发生器能够产生宽而稳定的梳状光谱。它们出色的可重构性是对集成克尔梳子的有力补充，支持从光谱学(16)到光通信8的各种应用。
Optical frequency combs consist of equally spaced discrete optical frequency components and are essential tools for optical communication, precision metrology, timing and spectroscopy(1-9). At present, combs with wide spectra are usually generated by mode-locked lasers(10) or dispersion-engineered resonators with third-order Kerr nonlinearity(11). An alternative method of comb production uses electro-optic (EO) phase modulation in a resonator with strong second-order nonlinearity, resulting in combs with excellent stability and controllability(12-14). Previous EO combs, however, have been limited to narrow widths by a weak EO interaction strength and a lack of dispersion engineering in free-space systems. Here we overcome these limitations by realizing an integrated EO comb generator in a thin-film lithium niobate photonic platform that features a large EO response, ultralow optical loss and highly colocalized microwave and optical fields(15), while enabling dispersion engineering. Our measured EO comb spans more frequencies than the entire telecommunications L-band (over 900 comb lines spaced about 10 gigahertz apart), and we show that future dispersion engineering can enable octave-spanning combs. Furthermore, we demonstrate the high tolerance of our comb generator to modulation frequency detuning, with frequency spacing finely controllable over seven orders of magnitude (10 hertz to 100 megahertz), and we use this feature to generate dual-frequency combs in a single resonator. Our results show that integrated EO comb generators are capable of generating wide and stable comb spectra. Their excellent reconfigurability is a powerful complement to integrated Kerr combs, enabling applications ranging from spectroscopy(16) to optical communications8.