Silica microlens arrays (MLAs) with multiple numerical-apertures (NAs) have high thermal and mechanical stability, and have potential application prospects in 3D display and rapid detection. However, it is still a challenge to rapidly fabricate silica MLAs with a larger range of NAs and how to obtain multiple NAs in the same aperture diameter. Here, a wet etching assisted spatially modulated femtosecond laser pulse fabricating technology is proposed. In this technology, Gaussian laser pulse is modulated in the axial direction to create a pulse with a large aspect ratio, which is used to modify the silica to obtain a longer modification distance than traditional technology. After that, a microlens with a larger NA can be obtained by etching, and the NA variable range can be up to 0.06–0.65, and even under the same aperture, the variable NA can range up to 0.45–0.65. In addition, a single focus is radially modulated into several focus with different axial lengths to achieve a single exposure fabricating of MLA with multiple NAs. In characterization of the image under a microscope, the multi-plane imaging characteristics of the MLA are revealed. The proposed technology offers great potential toward numerous applications, including microfluidic adaptive imaging and biomedical sensing.

Optical security involving the use of light to achieve distinctive vision effects has become a widely used approach for anticounterfeiting. Holographic multiplexing has attracted considerable interest in multiplexing security due to its high degree of freedom for manipulating the optical parameters of incident laser beams. However, the complex and time-consuming fabrication process of metasurface-based holograms and the sophisticated nature of holographic imaging systems have hindered the practical application of holographic multiplexing in anticounterfeiting. Combining holography with shape memory polymers to construct reconfigurable holograms provides a simple and efficient way for holographic multiplexing. This paper proposes a reconfigurable fourlevel amplitude hologram fabricated on a heat-shrinkable shape memory polymer using spatially modulated femtosecond laser pulses. Simply by triggering the shape recovery of the polymer through heating, the amplitude modulation of light by the hologram is reconfigured through the shrinking of processed microcrater pixels with three diameters, which enables variation to be achieved in reconstructed holographic images. Examples of holographic multiplexing and data encryption are used to validate the proposed method. The proposed economic and simple approach for holographic multiplexing provides an integrated and single-material solution to packaging and optical security, which has extensive potential in anticounterfeiting and optical encryption.

The design of micro/nanostructures on silicon-on-insulator (SOI) devices has attracted widespread attention in the science and applications of integrated optics, which, however, are usually restricted by the current manufacturing technologies. Hence, in this paper, we propose a mask-free, one-step femtosecond laser lithography method for efficient fabrication of high-quality controllable planar photonic structures on SOI devices. Subwavelength gratings with high uniformity are flexibly prepared on a SOI wafer, and they can be efficiently extended for large-area fabrication with long-range uniformity. Different from the melt flow mechanism to bulk silicon, the buried SiO2 layer of the SOI material provides substantial control over the phase change process, thereby achieving local rapid vaporization to form a high-quality structure. The optical properties of the prepared structures are measured experimentally and determined to possess powerful diffraction and light-coupling characteristics. Strikingly, active control of the SOI surface structure morphology, from the grating to the periodic silicon wire structure, can be realized through precision adjustment of the pulse injection volumes. A homogeneous silicon photonic wire is successfully generated on the SOI device, providing an alternative to the preparation of waveguides. This effective femtosecond laser lithography method for fabricating controllable photonic structures on SOI devices is expected to further promote the development of integrated optics.

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We developed a novel method for fabricating microlenses and microlens arrays by controlling numerical aperture (NA) through temporally shaped femtosecond laser on fused silica. The modification area was controlled through the pulse delay of temporally shaped femtosecond laser. The final radius and sag height were obtained through subsequent hydrofluoric acid etching. Electron density was controlled by the temporally shaped femtosecond laser, and the maximum NA value (0.65) of a microlens was obtained in the relevant studies with femtosecond laser fabrication. Furthermore, the NA can be continuously adjusted from 0.1 to 0.65 by this method. Compared with the traditional methods, this method exhibited high flexibility and yielded microlenses with various NAs and microlens arrays to meet the different demands for microlens applications.