Rewritable and Tunable Laser-Induced Optical Gratings in Phase-Change Material Films

Abstract

Laser-induced periodic surface structures (LIPSS) can be fabricated in virtually all types of solid materials and show great promise for efficient and scalable production of surface patterns with applications in various fields from photonics to engineering. While the majority of LIPSS manifest as modifications of the surface relief, in special cases, laser impact can also lead to periodic modulation of the material phase state. Here, we report on the fabrication of high-quality periodic structures in the films of phase-change material Ge2Sb2Te5 (GST). Due to considerable contrast of the refractive index of GST in its crystalline and amorphous states, the fabricated structures provide strong spatial modulation of the optical properties, which facilitates their applications. By changing the excitation laser wavelength, we observe the scaling of the grating period as well as transition between formation of different types of LIPSS. We optimize the laser exposure routine to achieve large-scale high-quality phase-change gratings with controllable period and demonstrate their reversible tunability through intermediate amorphization steps. Our results reveal the prospects of fast and rewritable fabrication of high-quality periodic structures for photonics and can serve as a guideline for further development of phase-change material-based optical elements.

Ten Open Questions about Laser-Induced Periodic Surface Structures

“…In a distinct optical approach, the grating-like spatial characteristics of LSFL can be imprinted in the sub-ablation regime to a phase change material (PCM) such as GeTe [94] or Ge 2 Sb 2 Te 5 [95], allowing the stripes/ridges of the LIPSS to be represented either by the amorphous or by the crystalline phase of the PCM. In this way, by proper choice of the laser irradiation parameters, micron-sized spots with an optically encoded LIPSS patterns can be written and erased again [95,96]. Such optical patterns may be used for information encoding or act as unique safety features.…”

Polarization-Based Idler Elimination: Enhancing the Efficiency of Optical Parametric Amplification

“…Wavelength tunable femtosecond laser sources are highly important in modern science. Research fields like spectroscopy [1][2][3], nonlinear imaging [4][5][6], laser micro processing [7][8][9] and nonlinear optics [10][11][12][13] greatly benefit from high peak and average power wavelength tunable femtosecond pulses, which are often produced using optical parametric amplification (OPA) devices. However, depending on various parameters such as signal wavelength and bandwidth, pump-to-signal conversion efficiency is usually limited to no more than 20% and often substantially less [14].…”

High-Uniformity Submicron Gratings with Tunable Periods Fabricated through Femtosecond Laser-Assisted Molding Technology for Deformation Detection

“…Although the optical diffraction limit can be reduced by reducing the wavelength of the laser used for direct writing to achieve submicron fabrication, the operation procedure is complicated, with high requirements for fabricating equipment and low fabricating efficiency. Femtosecond laser-induced periodic surface structures (LIPSSs), which are capable of overcoming the diffraction limit, have been widely used in the fabrication of submicron gratings. − Vorobyev and Guo reported that different colors were visible on the surface of aluminum with LIPSSs depending on the viewing angle . Bolle, Hiraoka, Dyer, and others have attempted to apply LIPSSs in the direct ablation fabrication of polymers; however, forming a uniform grating on the polymer surface through direct ablation is difficult, and the method therefore does not meet the requirements for optical applications. − Recently, Huang et al proposed a nonablative femtosecond laser fabrication technology that greatly improved the uniformity of grating fabricated on a silicon surface; , however, the usability of this technology on flexible substrates has not been further investigated.…”