Beyond 100 THz-spanning ultraviolet frequency combs in a non-centrosymmetric crystalline waveguide
Beyond 100 THz-spanning ultraviolet frequency combs in a non-centrosymmetric crystalline waveguide
复制标题
DOI：
10.1038/s41467-019-11034-x
复制
发表时间：
2019-07-05
影响因子：
16.6
通讯作者：
Tang, Hong X.
中科院分区：
文献类型：
--
作者：
Liu, Xianwen;Bruch, Alexander W.;Tang, Hong X.
紫外线频率梳通过处理原子和分子的电子跃迁，实现了从精密光谱到原子钟的各种应用。通过集成的非线性光学获得紫外光通常会受到紫外区强烈的材料色散和大的波导关注的阻碍。在这里，我们演示了一种简单的芯片规模紫外线梳状发生器的方法，同时显示了128太赫兹的无间隙频率范围和高转换效率。这一过程依赖于由超快光纤激光器提供的近可见超连续谱的绝热平方频率平移。在单晶氮化铝薄膜中实现了同时的立方和二次非线性过程，其中啁啾调制的锥形波导被图案化以确保宽的相位匹配。外差特性表明，近可见光和紫外超连续谱都保持了很高的相干性。我们的方法也适用于其他具有可扩展带宽的超快非线性光学的非中心对称光子平台。
Ultraviolet frequency combs enable applications ranging from precision spectroscopy to atomic clocks by addressing electronic transitions of atoms and molecules. Access to ultraviolet light via integrated nonlinear optics is usually hampered by the strong material dispersion and large waveguide attention in ultraviolet regions. Here we demonstrate a simple route to chip-scale ultraviolet comb generators, simultaneously showing a gap-free frequency span of 128 terahertz and high conversion efficiency. This process relies on adiabatic quadratic frequency translation of a near-visible supercontinuum sourced by an ultrafast fiber laser. The simultaneous cubic and quadratic nonlinear processes are implemented in single-crystalline aluminum nitride thin films, where chirp-modulated taper waveguides are patterned to ensure a broad phase matching. The heterodyne characterization suggests that both the near-visible and ultraviolet supercontinuum combs maintain high coherence. Our approach is also adaptable to other non-centrosymmetric photonic platforms for ultrafast nonlinear optics with scalable bandwidth.