Research under the ENIGMA project has yielded a number of results in fundamentals and applications of engineering material properties by advanced ultrafast laser writing.
High speed ultrafast laser nanostructuring by advanced energy deposition control (Optica, 8 (2021))
Ultrafast laser writing via microexplosion and isotropic nanovoid formation in transparent materials and its application to three-dimensional (3D) optical data storage was first demonstrated in 1996. Although the data density can be improved by using five-dimensional (5D) optical data storage by anisotropic nanostructures in transparent materials, high writing speed and density remains a major challenge for real-world applications. In our recent paper (Lei, Y., Sakakura, M., Wang, L., Yu, Y., Wang, H., Shayeganrad, G., & Kazansky, P.G. “High speed ultrafast laser anisotropic nanostructuring by energy deposition control via near-field enhancement”, Optica, Vol. 8, Issue 11, pp. 1365-1371 (2021)) we demonstrated high speed ultrafast laser anisotropic nanostructuring in silica glass by energy deposition control via near-field enhancement. The anisotropic nanolamella-like void structure is created via near-field enhancement from an microexplosion produced isotropic nanovoid. The nanostructures are exploited for 5D data storage with a writing rate of mega voxels/s, corresponding to a data recording speed of ~225 kB/s and a potentially high capacity of hundreds of TB/disc.
Multilayer error-Free 5D optical data storage by ultrafast laser nanostructuring in glass (submitted to Laser and Photonics Reviews, (2021))
The demand for energy efficient data storage technologies with high capacity and long lifespan is increasingly growing due to the explosion of digital information. In our recent paper (Wang, H., Lei, Y., Wang, L., Sakakura, M., Yu, Y., Shayeganrad, G., & Kazansky, P. G., “100-layer error-free 5D optical data storage by ultrafast laser nanostructuring in glass”, submitted to Laser and Photonics Reviews, (2021)) a five dimensional (5D) optical data storage with high capacity and ultralong lifetime is realized in silica glass by femtosecond laser-induced elongated nanopores (type X modification). The ultrahigh transmission of this birefringent modification, >99% in the visible range, allows recording and retrieving thousands of layers of multibit digital data practically. Furthermore, The Hitchhiker's Guide to the Galaxy is optically recorded with a data writing speed of 8 kB/s in 100-layer voxels and the proven data readout accuracy of 100%.
Laser Writing Creates Flat Optics in Glass (Light: Science & Applications, 9 (2020))
Conventional optics control the wavefront by the optical path or thickness and refractive index of their constituent materials. In our paper (Sakakura, M., Lei, Y., Wang, L., Yu, Y. H., & Kazansky, P. G., “Ultralow-loss geometric phase and polarization shaping by ultrafast laser writing in silica glass”, Light: Science & Applications, 9(1), 1-10, (2020); doi: 10.1038/s41377-020-0250-y) we reported a laser-writing method in silica glass that advances flat optics that exploits the geometric phase. New type of ultrafast laser birefringence nano-patterning in silica glass provides ultra-low scattering loss, coined as Type X modification. Low-loss modification is also crucial for achieving high-capacity polarization multiplexed 5D optical memory in glass.
Femtosecond laser-induced metamaterial nanostructures for smart window applications (ACS Applied Materials & Interfaces, 12 (2020))
Smart window is an important strategy to improve the energy efficiency of buildings. A tunable metamaterial-based nanopatterned VO2 thin film is produced for the first time using ultrashort laser pulses and examined for thermochromic smart window application (Bhupathi, S., Wang, S., Abutoama, M., Balin, I., Wang, L., Kazansky, P. G., & Abdulhalim, I., “Femtosecond laser-induced vanadium oxide metamaterial nanostructures and the study of optical response by experiments and numerical simulations”, ACS Applied Materials & Interfaces, 12(37), 41905-41918, (2020)). The structures show enhanced transmittance in the near-infrared (NIR) region, with an improvement in NIR and solar modulation opening a new gateway for smart devices.
Self‐organized crystallization in unconventional glasses created by ultrafast laser irradiation (Advanced Optical Materials, 7 (2019), Advanced Optical Materials, 9 (2021)
The construction of functional photonic structures in transparent solids is required for various applications, such as 3D displays and optical information processing. In our paper (Zhang, B., Tan, D., Liu, X., Tong, L., Kazansky, P. G., & Qiu, J., “Self‐organized periodic crystallization in unconventional glass created by an ultrafast laser for optical attenuation in the broadband near‐infrared region”, Advanced Optical Materials, 7(20), 190059, (2019)), self-assembled crystallite-based grating nanostructures were created in an unconventional multicomponent glass with an ultrafast laser. Broadband variable near-infrared optical attenuators with a high attenuation ratio were demonstrated. In our paper (Zhang, B., Wang, Z., Tan, D., Liu, X., Xu, B., Tong, L., Kazansky, P. G & Qiu, J., “Ultrafast laser inducing continuous periodic crystallization in the glass activated via laser‐prepared crystallite‐seeds,” Advanced Optical Materials, 9(8), 2001962, (2021)) a dynamic process of ultrafast laser-induced continuous periodic crystallization to generate self-organized crystal arrays inside the glass is reported. This work not only opens an avenue for creating embedded periodic crystalline patterns with extremely high efficiency but also helps to clarify the dynamics of ultrafast laser nanostructuring inside transparent dielectrics.
Complete spatiotemporal and polarization characterization of ultrafast vector beams (Communications Physics, 3 (2020))
The use of structured ultrashort pulses with coupled spatiotemporal properties is emerging as a key tool for ultrafast manipulation. Ultrafast vector beams are opening exciting opportunities in different fields such as microscopy, time-resolved imaging, nonlinear optics, particle acceleration or attosecond science. In our work (Alonso, B., Lopez-Quintas, I., Holgado, W., Drevinskas, R., Kazansky, P. G., Hernández-García, C., & Sola, Í. J., “Complete spatiotemporal and polarization characterization of ultrafast vector beams”, Communications Physics, 3(1), 1-10, (2020)), we implemented a technique for the full characterization of structured time-dependent polarization light waveforms with spatiotemporal resolution, using polarization convertors fabricated by ultrafast laser nanostructuring and incorporated in a compact twofold spectral interferometer, based on in-line bulk interferometry and fibre-optic coupler assisted interferometry. The results pave the way for the full characterization of the most complex waves created up to now.
