Paz-Buclatin Franzette, Esquivel-González Marcos, Casasnovas-Melián Alfredo, de Varona Omar, Cairós Carlos, Trujillo-Sevilla Juan Manuel, Kamada Kei, Yoshikawa Akira, Rodríguez-Ramos Jose Manuel, Martin Leopoldo Luis, Ródenas Airan
Department of Physics, Universidad de La Laguna, La Laguna, Spain.
Department of Physics, Universidad de La Laguna, Avda. Astrofísico Francisco Sáncehez, S/N, Facultad de ciencias, La Laguna, Santa Cruz de Tenerife 38200, Spain.
Nanophotonics. 2023 Jan 11;12(8):1511-1525. doi: 10.1515/nanoph-2022-0665. eCollection 2023 Apr.
The fabrication of three-dimensional (3D) nanostructures within optical materials is currently a highly sought-after capability. Achieving nanoscale structuring of media within its inner volume in 3D and with free design flexibility, high accuracy and precision is a development yet to be demonstrated. In this work, a 3D laser nanolithography technique is developed which allows producing mm-long hollow nanopores inside solid-state laser crystals and with a high degree of control of pore cross-sectional aspect ratio and size. We report an in-depth study on the formation of pores both within the non-thermal regime at which temperature is fast dissipated after each laser pulse, and for a thermally controlled regime using pulse-bursts which facilitate the formation of pores with highly circular shapes down to 1.1. We demonstrate this process for a wide range of speeds, pulse repetition rates and pulse energies, thus opening the door to a much more useful nanofabrication technique for nanophotonics. Finally, we also report the change in index of refraction that is produced at the nanoscale obtaining a positive index contrast of ∼3%. The work therefore provides a promising path towards reliable 3D nanostructuring of solid-state laser media for the flexible fabrication of large and complex structures with features sizes from the nanoscale up to the mm-scale. Moreover, due to the embedded, seamless, and monolithic nature of this technology, and since YAG crystals can sustain temperatures of up to 1900 °C and are highly chemically inert and erosion resistant, we anticipate its direct application in harsh environments.
在光学材料中制造三维（3D）纳米结构目前是一项备受追捧的能力。在介质内部体积中实现三维纳米级结构化，且具有自由设计灵活性、高精度和高精准度，这一发展尚未得到证实。在这项工作中，开发了一种3D激光纳米光刻技术，该技术能够在固态激光晶体内部制造毫米长的中空纳米孔，并能高度控制孔的横截面纵横比和尺寸。我们报告了一项深入研究，内容涉及在非热 regime（每个激光脉冲后温度迅速消散）以及使用脉冲串的热控 regime 中孔的形成情况，脉冲串有助于形成形状高度圆形、低至1.1的孔。我们在广泛的速度、脉冲重复率和脉冲能量范围内展示了这一过程，从而为纳米光子学开启了一种更有用的纳米制造技术之门。最后，我们还报告了在纳米尺度产生的折射率变化，获得了约3%的正折射率对比度。因此，这项工作为固态激光介质可靠的三维纳米结构化提供了一条有前景的途径，可用于灵活制造从纳米尺度到毫米尺度的大型复杂结构。此外，由于该技术具有嵌入式、无缝和整体式的性质，并且由于YAG晶体能够承受高达1900°C的温度，具有高度的化学惰性和抗侵蚀性，我们预计它将直接应用于恶劣环境。
