Nanoantennas made of high-index semiconductors with a strong nonlinearity and supported optical Mie-type resonances offer a promising alternative platform for nonlinear nanophotonics. In this Letter, we employ an array of amorphous silicon nanodisks with varying diameters to produce a broadband deep-ultraviolet third harmonic of a few-cycle Ti:sapphire oscillator. Ultrashort light pulses efficiently deposit their energy at the center of the disks where the electric field is strongly amplified by the anapole states. This leads to a progressive material modification in an extreme multishot (>10¹⁰ pulses) and a rather low fluence (<10^–3 J/cm²) regime, drastically differing from other known mechanisms, such as nonthermal plasma annealing or thermal melting-induced recrystallization. We suggest that the material modification is due to femtosecond laser-induced excitation of dangling bonds, which leads to a gradual boosting of the third harmonic conversion efficiency and broadening of its spectral bandwidth.

中文翻译：

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几个周期激光辐射过程中的渐进式自增强磁极增强型深紫外三次谐波

由具有强非线性和支持光学Mie型共振的高折射率半导体制成的纳米天线为非线性纳米光子学提供了一个有希望的替代平台。在这封信中，我们采用了一系列直径可变的非晶硅纳米盘来产生几个周期的Ti：蓝宝石振荡器的宽带深紫外三次谐波。超短光脉冲将能量有效地沉积在磁盘的中心，在磁盘的中心，电场被偶极子态强烈放大。这导致在极端的多重发射（> 10 ^10个脉冲）和相当低的注量（<10 ^–3 J / cm ²）中进行渐进的材料修改。）机制，与其他已知机制（例如非热等离子体退火或热熔融诱导的重结晶）大不相同。我们认为，材料改性是由于飞秒激光诱导的悬空键激发，从而导致三次谐波转换效率逐渐提高，其谱带宽变宽。