The combination of phase change materials and metasurfaces has enabled myriads of versatile platforms for dynamic wave control, especially for various applications in integrated photonics and optoelectronics. In this paper, an electrically reconfigurable metasurface is demonstrated to work as a terahertz (THz) broadband digital switch by integration of vanadium dioxide (VO2). In such integrated optoelectronic frameworks, active and bistable digital control of optical responses is enabled by applying electrical stimuli to vertically cascaded metasurfaces with broadband behaviors for Joule heating that causes phase change and state switching. Before and after phase change, a high contrast ratio of transmittance is demonstrated within a broad THz range up to 400 GHz. Essentially, fast switching can be guaranteed compared with current devices based on thin film phase change materials, due to the local electrical heating that proves inherently efficient and faster to trigger the phase transition process. As a result, such active optoelectronic framework based on phase change materials may pave a new way for emerging integrated devices such as photoelectric switch, photonic memory, signal processing and so on
Dimensional metrology for micro structure plays an important role in addressing quality issues and observing the performance of micro-fabricated products. Different from the traditional white-light interferometry approach, the modulation-based method is expected to measure topography of micro structure by the obtained modulation of each interferometry image. Through seeking the maximum modulation of every pixel respectively in Z direction, the method could obtain the corresponding height of individual pixel and finally get topography of the structure. Owing to the characteristic of modulation, the proposed method which is not influenced by the change of background light intensity caused by instable light source and different reflection index of the structure could be widely applied with high stability. The paper both illustrates the principle of this novel method and conducts the experiment to verify the feasibility.
The spectrum-integral Talbot lithography (STIL) was introduced into the fabrication of one-dimensional micro gratings using the broad-band UV illumination in this paper. In the process of spectrum-integral Talbot lithography, the self-images and π-phase-shifted images generated by different wave lengths overlap and integrate collectively to enormously extend the continuous depth-of-focus area since a certain distance away from the mask. As a result, the route of STIL proves to be of great potential for periodic frequency-doubling in good contrast without any complex improvement and operation to the traditional proximity lithographic system of UV mask aligner.
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