Mechanical displacement is one of the mechanisms that can be utilized for realizing tunable optical metasurfaces. We propose nano-electromechanically tunable metasurfaces based on slot mode resonances at telecom wavelength. Utilizing high aspect ratio silicon slabs that can bend towards each other on a substrate, we achieve a robust device that can cover large areas. Upon applying 40 V, the device can achieve 4 nm spectral shift which gives rise to a 70% amplitude modulation. At the cost of a higher power consumption, the proposed device is mechanically robust and can be used in beam steering, modulation and wavefront shaping.
Three-dimensional elements, with refractive index distribution structured at subwavelength scale, provide an expansive optical design space that can be harnessed for demonstrating multifunctional free-space optical devices. We present three dimensional dielectric elements, designed to be placed on top of the pixels of image sensors that provide different functionalities like sorting and focusing of light based on its color and polarization with efficiency significantly surpassing two dimensional absorptive and diffractive filters, and ultra-compact polarimetry. The devices are designed via iterative gradient-based optimization to account for multiple target functions while ensuring compatibility with existing nanofabrication processes, and they are experimentally validated using a scaled device that operates at microwave frequencies. This approach combines arbitrary functions into a single compact element, even where there is no known equivalent in bulk optics, enabling novel integrate
Inverse design has opened up the possibility of achieving high photonic device performances over broad spectral ranges. Recently, we have applied this technique to broadband polarization splitting. By sorting an input polarization state of light into four analyzer directions, the projection onto each of which is focused to a different detector element, we design a device that can reconstruct the polarization state. This concept has been shown with metasurfaces, but over a limited bandwidth. We show simulation results for a wide bandwidth device that efficiently sorts along four polarization directions, achieving high transmission and large contrast between the different states.
We present a visible light interference lithography technique that utilizes a 2x2 cm metasurface mask to enable fabrication of 8x8 cm continuous and homogenous nano-architected materials. Patterns are resolved both in commercial 20-60 um films of SU-8 and >20 um films of custom glycidyl methacrylate-derived negative-tone photoresists. The combination of our metasurface-enabled large-scale 3D patterning technique with customizable photoresist chemistry provides a new pathway for scalable production of architected materials with nanometer feature resolution and advanced functional properties. Impact experiments using Laser-Induced Particle Impact Testing (LIPIT) were conducted to probe mechanical response and material homogeneity.
With modern nanofabrication technology, researchers and companies can reliably produce 3-dimensional patterns with feature sizes much smaller than the wavelength of visible light. The ability to do this in a scalable fashion brings nanophotonic research into the realm of commercial technology. For example, metasurfaces achieve high optical performance in fractions of the thickness of traditional bulky optical components and can be designed for unique, custom functionalities. By expanding the design space beyond the metasurface regime and allowing for photonic designs in full three dimensions, we can further increase the degrees of freedom at our disposal. This new design space is complex and inherently involves multiply scattering structures. In order to efficiently search for good solutions, we use an inverse design procedure based on the adjoint variable method. Taking advantage of this large design space, we can computationally optimize multi-functional meta-optical devices that achieve novel functionalities in minimal footprints. We demonstrate wavelength splitting photonic filters with application to color filter arrays on modern-day image sensors. These filters are designed to replace absorbing filters and instead re-route colors to specific sensor locations, thus recovering previously lost transmission. We show that these devices work with a variety of realistic fabrication restrictions and demonstrate their abilities experimentally in the microwave regime where we can realize layered devices via simple techniques like 3D printing. Finally, we comment on potential future applications and avenues where inverse design can help solve inherently difficult engineering challenges in nanophotonics.
Single-photon avalanche diodes (SPADs) have been widely used to push the frontier of scientific research (e.g., quantum science and single-molecule fluorescence) and practical applications (e.g., Lidar). However, there is a typical compromise between photon detection efficiency and jitter distribution. The light-trapping SPAD has been proposed to break this trade-off by coupling the vertically incoming photons into a laterally propagating mode while maintaining a small jitter and a thin Si device layer. In this work, we provide a 3D-based optical and electrical model based on practical fabrication conditions and discuss about design parameters, which include surface texturing, photon injection position, device area, and other features.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.