Ultra-compact Form Factor Research Articles

Metasurface-Embedded Contact Lenses for Holographic Light Projection.

Contact lenses have been instrumental in vision correction and are expected to be utilized in augmented reality (AR) displays through the integration of electronic and optical components. In optics, metasurfaces, an array of sub-wavelength nanostructures, have offered optical multifunctionality in an ultra-compact form factor, facilitating integration into various imaging, and display systems. However, transferring metasurfaces onto contact lenses remains challenging due to the non-biocompatible materials of extant imprinting methods and the structural instability caused by the swelling and shrinking of the wetted surface. Here, a biocompatible method is presented to transfer metasurfaces onto contact lenses using hyaluronic acid (HA) as a soft mold and to allow for holographic light projection. A high-efficiency metahologram is obtained with an all-metallic 3D meta-atom enhanced by the anisotropy of a rectangular structure, and a reflective background metal layer. A corrugated metal layer on the HA mold is supported with a SiO2 capping layer, to avoid unwanted wrinkles and to ensure structural stability when transferred to the surface of pliable and wettable contact lenses. Biocompatible method of transferring metasurfaces onto contact lenses promises the integration of diverse optical components, including holograms, lenses, gratings and more, to advance the visual experience for AR displays and human-computer interfaces.

Phase change material metasurface loading enables an ultrafast all-optically switchable, compact, narrowband freespace optical filter

Active metasurfaces leveraging phase change materials (PCMs) remain a subject of intense investigation, owing to their inherent tunable properties and successful integration into integrated photonics. By harnessing the ultra-compact form factor of optical metasurfaces, further advancements in switching speeds and reduction in switching energies have the potential to revolutionize applications in free space optical communication, optical signal processing, neuromorphic photonics, quantum photonics, and compact LiDAR. In this context, an ultrafast all-optically switchable narrowband spectral filter employing a distributed Bragg reflector cavity loaded with a PCM-metasurface is proposed. The work involves a comprehensive numerical exploration of its optical properties, encompassing design optimization and anticipating limits in switching speeds and energy requirements. Specifically, focusing on a GST225 metasurface operating in the shortwave-infrared spectrum, the numerical investigations reveal the potential to achieve transmission contrast levels as high as 24 dB, accompanied by Q-factors up to a thousand and less than 1 dB insertion loss. This performance notably outperforms recently reported free-standing PCM metasurfaces and cavities loaded with unstructured PCM thin films. Furthermore, the study predicts full-cycle reconfigurability (transitioning from amorphous to crystalline states and vice versa) with anticipated switching speeds of 91 & 200 MHz and switching fluence of 0.655 & 0.616 mJ/cm2 per cycle for the RESET and SET processes respectively. This investigation holds promise for advancing the state-of-the-art performance of PCM-based metasurfaces.

Preview the Products on Display at Display Week 2023

Preview the Products on Display at Display Week 2023

Ultra-Wideband Switched-Capacitor Delays and Circulators—Theory and Implementation

Recent research has revealed the possibility to achieve non-magnetic non-reciprocity using time variance. However, prior CMOS-based circulators rely on the interference between non-reciprocal switched-capacitor/transmission-line gyrators and reciprocal transmission-line rings, which increases form factor and restricts frequency tunability and bandwidth (BW). On the other hand, our recent work on quasi-electrostatic wave propagation in switched-capacitor networks has proposed a new regime in multipath switched-capacitor network operation that enables an ultra-broadband, ultra-compact reciprocal/non-reciprocal true-time-delay element. In this work, we corroborate these findings by implementing prototype devices of the quasi-electrostatic delay element. Our measurements of the delay element reveal that delays of tens of nanoseconds over hundreds of MHz BW are realizable on-chip in a compact form factor. In addition, we apply synthetic rotation across these switched-capacitor networks to realize an ultra-broadband N-port circulator with ultra-compact form factor. We implemented a wideband three-port circulator showcasing this new architecture in a standard 65-nm CMOS process. The circulator exhibits symmetric performance across all three ports and dc-1-GHz operation for a modulation frequency of 500 MHz. The measured transmission losses of the circulator range between 3.1 and 4.3 dB, matching is-15 dB, isolation is >18 dB, and noise figure (NF) is consistent with the insertion loss. This device occupies an area of 0.19 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ( λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">center</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> /1.9×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> ), representing about 100-1000 × higher miniaturization compared to the prior art.

Focus on photonics, spectroscopy, and spectrometry

Focus on photonics, spectroscopy, and spectrometry

A 25.78-Gbit/s × 4-ch Active Optical Cable with Ultra-Compact Form Factor for High-Density Optical Interconnects

A 25.78-Gbit/s × 4-ch active optical cable (AOC) with an ultra-compact form factor is proposed. The size of the proposed AOC is 5.2 cm3, which is 55% smaller than the standard form factor of Quad Small Form-factor Pluggable (QSFP28), and 45% smaller than that of Micro Quad Small Form-factor Pluggable (μQSFP). As a result of utilizing a high-efficiency heat-dissipation structure and optimizing signal transmission lines and ground vias, the proposed AOC achieves high-heat dissipation and low-crosstalk characteristics. Furthermore, the proposed AOC demonstrated 25.78-Gbit/s error-free optical transmission over a 100-m Optical Multimode 3 (OM3) multimode fiber under all-channels (4-ch) operation and case temperature (Tc) of 70 °C.

Ultracompact CMOS-compatible optical logic using carrier depletion in microdisk resonators

We present a CMOS-compatible optoelectronic directed logic architecture that achieves high computational throughput (number of operations per second per unit area) by its ultracompact form factor. High speed-to-power performance is also achieved, by the low capacitance and high junction-to-mode overlap of low-radii SOI vertical pn junction microdisk switches. By using wavelength-division multiplexing and two electrical control signals per disk, each switch performs (N)OR, (N)AND, and X(N)OR operations simultaneously. Connecting multiple switches together, we demonstrate higher-order scalability in five fundamental N-bit logic circuits: AND/OR gates, adders, comparators, encoders, and decoders. To the best of our knowledge, these circuits achieve the lowest footprint of silicon-based multigigabit-per-second optical logic devices in literature.

A Fully Differential Ultra-Compact Broadband Transformer-Based Wilkinson Power Divider

This letter presents a fully differential and integrated transformer-based Wilkinson power divider with a broad bandwidth, low loss, high isolation, and an ultra-compact form factor. Two differential transformers connected in parallel serve as the impedance transforming and power combining network in the proposed Wilkinson power divider. Shunt capacitors are added between the output ports for matching and isolation enhancement. A proof-of-concept transformer-based Wilkinson power divider is designed at 60 GHz and implemented in a standard 130 nm SiGe BiCMOS process with the core chip area of $270 \mu\text{m} \times 107 \mu\text{m}$ and the simulated 1 dB-magnitude fractional bandwidth of 64% at the 60 GHz center frequency. Measurement results of 4 independent samples demonstrate the passive loss of 1.32 dB at 62 GHz with standard deviation of 0.1 dB and the peak isolation of 28 dB at 65 GHz with magnitude and phase imbalance within 0.2 dB and 5 $^{\circ}$ , respectively.

Fabrication of microoptical freeform arrays on wafer level for imaging applications.

Miniaturized imaging systems combining an ultra-compact form factor in combination with the ability of refocusing and depth imaging have gained much interest in the field of mobile imaging. Therefore, artificial compound eye cameras are an extremely promising approach for the realization of compact monolithic camera modules on wafer level. Up to now, their imaging performance was limited to low resolution in the range of VGA format according to fabrication constrains given by the established microoptical fabrication methods, namely the reflow of photoresist. In order to overcome these classical limitations, the use of refractive freeform arrays (RFFA) instead of conventional microlens arrays is inevitable. To enable high volume and cost efficient mass production of artificial compound eye cameras for mass markets like the consumer electronics industry, their fabrication on wafer level is essential, but has not been published up to now. We present a wafer level based process chain enabling the fabrication of these elements for the first time.

Design of a subnanometer resolution beam position monitor for dielectric laser accelerators

We present a new concept for a beam position monitor with the unique ability to map particle beam position to a measurable wavelength. Coupled with an optical spectrograph, this beam position monitor is capable of subnanometer resolution. We describe one possible design, and through finite-element frequency-domain simulations, we show a resolution of 0.7 nm. Because of its high precision and ultracompact form factor, this device is ideal for future x-ray sources and laser-driven particle accelerators "on a chip."