Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userFast Extended Depth of Focus Meta-Optics for Varifocal Functionality
107
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
Extended depth of focus (EDOF) optics can enable lower complexity optical imaging systems when compared to active focusing solutions. With existing EDOF optics, however, it is difficult to achieve high resolution and high collection efficiency simultaneously. The subwavelength pitch of meta-optics enables engineering very steep phase gradients, and thus meta-optics can achieve both a large physical aperture and high numerical aperture. Here, we demonstrate a fast (f/1.75) EDOF meta-optic operating at visible wavelengths, with an aperture of 2 mm and focal range from 3.5 mm to 14.5 mm (286 diopters to 69 diopters), which is a 250 elongation of the depth of focus relative to a standard lens. Depth-independent performance is shown by imaging at a range of finite conjugates, with a minimum spatial resolution of ~9.84{mu}m (50.8 cycles/mm). We also demonstrate operation of a directly integrated EDOF meta-optic camera module to evaluate imaging at multiple object distances, a functionality which would otherwise require a varifocal lens.
rate research
Read More
Three-dimensional elements, with refractive index distribution structured at sub-wavelength scale, provide an expansive optical design space that can be harnessed for demonstrating multi-functional free-space optical devices. Here we present 3D dielectric elements, designed to be placed on top of the pixels of image sensors, that sort and focus light based on its color and polarization with efficiency significantly surpassing 2D absorptive and diffractive filters. The devices are designed via iterative gradient-based optimization to account for multiple target functions while ensuring compatibility with existing nanofabrication processes, and 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 integrated photonic applications.
Optical metasurfaces have shown to be a powerful approach to planar optical elements, enabling an unprecedented control over light phase and amplitude. At that stage, where wide variety of static functionalities have been accomplished, most efforts are being directed towards achieving reconfigurable optical elements. Here, we present our approach to an electrically controlled varifocal metalens operating in the visible frequency range. It relies on dynamically controlling the refractive index environment of a silicon metalens by means of an electric resistor embedded into a thermo-optical polymer. We demonstrate precise and continuous tuneability of the focal length and achieve focal length variation larger than the Rayleigh length for voltage as small as 12 volts. The system time-response is of the order of 100 ms, with the potential to be reduced with further integration. Finally, the imaging capability of our varifocal metalens is successfully validated in an optical microscopy setting. Compared to conventional bulky reconfigurable lenses, the presented technology is a lightweight and compact solution, offering new opportunities for miniaturized smart imaging devices.
Metasurface optics have demonstrated vast potential for implementing traditional optical components in an ultra-compact and lightweight form factor. Metasurface lenses, also called metalenses, however, suffer from severe chromatic aberrations, posing serious limitations on their practical use. Existing approaches for circumventing such aberrations via dispersion engineering are limited to small apertures and often entails multiple scatterers per unit cell with small feature sizes. Here, we present an alternative technique to mitigate chromatic aberration and demonstrate high-quality, full-color imaging using extended depth of focus (EDOF) metalenses and computational reconstruction. Previous EDOF metalenses relied on cubic phase masks that induced asymmetric artifacts in images, whereas here we demonstrate the use of symmetric phase masks that can improve subsequent image quality, including logarithmic-aspherical, and shifted axicon masks. Our work will inspire further development in achromatic metalenses beyond dispersion engineering and open new research avenues on hybrid optical-digital metasurface systems.
Compact varifocal lenses are essential to various imaging and vision technologies. However, existing varifocal elements typically rely on mechanically-actuated systems with limited tuning speeds and scalability. Here, an ultrathin electrically controlled varifocal lens based on a liquid crystal (LC) encapsulated semiconductor metasurface is demonstrated. Enabled by the field-dependent LC anisotropy, applying a voltage bias across the LC cell modifies the local phase response of the silicon meta-atoms, in turn modifying the focal length of the metalens. In a numerical implementation, a voltage-actuated metalens with continuous zoom and up to 20% total focal shift is demonstrated. The concept of LC-based metalens is experimentally verified through the design and fabrication of a bifocal metalens that facilitates high-contrast switching between two discrete focal lengths upon application of a 3.2 V$_{rm pp}$ voltage bias. Owing to their ultrathin thickness and adaptable design, LC-driven semiconductor metasurfaces open new opportunities for compact varifocal lensing in a diversity of modern imaging applications.
Modern-day computers use electrical signaling for processing and storing data which is bandwidth limited and power-hungry. These limitations are bypassed in the field of communications, where optical signaling is the norm. To exploit optical signaling in computing, however, new on-chip devices that work seamlessly in both electrical and optical domains are needed. Phase change devices can in principle provide such functionality, but doing so in a single device has proved elusive due to conflicting requirements of size-limited electrical switching and diffraction-limited photonic devices. Here, we combine plasmonics, photonics and electronics to deliver a novel integrated phase-change memory and computing cell that can be electrically or optically switched between binary or multilevel states, and read-out in either mode, thus merging computing and communications technologies.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
