Parallel fabrication of silicon concave microlens array by femtosecond laser irradiation and mixed acid etching

A method of multi-beam femtosecond laser irradiation combined with modified HF-HNO3-CH3COOH etching is used for the parallel fabrication of all-silicon piano-concave microlens arrays （MLAs）. The laser beam is split by a diffractive optical element and focused by a lens to drill microholes parallely on silicon. An HF-HNO3-H2SO4-CH3COOH solution is used to expand and polish laser-ablated microholes to form micro- lenses. Compared with the HF-HNO3-CH3COOH solution, the solution with H2SO4 can effectively reduce the etched surface roughness. The morphologies of MLAs at different laser powers and pulse numbers are observed. The image array formed by the silicon microlenses is also demonstrated.

Microlens arrays prepared via colloidal microsphere templating

A simple and efficient templating method in combination with hot embossing technique is developed for fabricating large-area two-dimensional（2D） microlens arrays（MLAs） with uniform shape.By utilizing a modified microchannel method,a 2D large-area hexagonal close-packed（HCP） array of silica colloidal microspheres is prepared and serves as a template in the following hot embossing treatment to create a polycarbonate（PC） microcavity array.Then,with the obtained PC microcavity structure serving as a mold,a hot embossing process is applied to finally achieve a polymethylmethacrylate（PMMA） MLA.The effect of annealing time during the mold preparation process on the dimensions and shapes of the prepared microlens is investigated.The imaging performances of the prepared PC concave microcavities and PMMA convex microlenses are characterized by carrying out projection experiments.Our method provides a rapid and low cost approach to prepare large-area MLAs.

Two-photon lithography for integrated photonic packaging

Photonic integrated circuits(PICs)have long been considered as disruptive platforms that revolutionize optics.Building on the mature industrial foundry infrastructure for electronic integrated circuit fabrication,the manufacturing of PICs has made remarkable progress.However,the packaging of PICs has often become a major barrier impeding their scalable deployment owing to their tight optical alignment tolerance,and hence,the requirement for specialty packaging instruments.Two-photon lithography(TPL),a laser direct-write three-dimensional(3-D)patterning technique with deep subwavelength resolution,has emerged as a promising solution for integrated photonics packaging.This study provides an overview of the technology,emphasizing the latest advances in TPL-enabled packaging schemes and their prospects for adoption in the mainstream photonic industry.

Imaging/nonimaging microoptical elements and stereoscopic systems based on femtosecond laser direct writing

The development of modern information technology has led to significant demand for microoptical elements with complex surface profiles and nanoscale surface roughness.Therefore,various micro-and nanoprocessing techniques are used to fabricate microoptical elements and systems.Femtosecond laser direct writing(FsLDW)uses ultrafast pulses and the ultraintense instantaneous energy of a femtosecond laser for micro-nano fabrication.FsLDW exhibits various excellent properties,including nonlinear multiphoton absorption,high-precision processing beyond the diffraction limit,and the universality of processable materials,demonstrating its unique advantages and potential applications in three-dimensional(3D)micro-nano manufacturing.FsLDW has demonstrated its value in the fabrication of various microoptical systems.This study details three typical principles of FsLDW,several design considerations to improve processing performance,processable materials,imaging/nonimaging microoptical elements,and their stereoscopic systems.Finally,a summary and perspective on the future research directions for FsLDW-enabled microoptical elements and stereoscopic systems are provided.