We introduce a scalable platform designed for very-large-scale programmable photonics, achieved through the integration of 300-mm-wafer-scale fabrication processes and in-house phase-change material fabrication. This approach enables reversible electrical tuning capabilities up to 50, 000 switching events. Moreover, we demonstrate a deterministic multilevel scheme capable of achieving 2^N optical levels, offering enhanced control and versatility in programmable photonics applications.
Sub-wavelength structuring of semiconductors has recently provided a powerful tool to engineer the dispersion of the light. Such structures, commonly known as meta-optics can achieve a non-trivial relation between the energy and momentum of photons. One particular possibility is to create a dispersion-free flat band, which allows a resonator to maintain the same resonance frequency for different incidence angles. In this work, we utilize a flat band meta-optic to create a photodiode which has a critically coupled absorption for a wide angular range (±18°). By implementing a lens-based concentrator, the size of the photodiode can remain small while collecting large amounts of light, which results in high resolution, low energy consumption, and fast operation speed of the photodiode.
Chalcogenide phase-change materials (PCMs) offer paradigms for programmable photonic integrated circuits thanks to their zero static energy and significant refractive index contrast. However, prototypical PCMs, such as Ge2Sb2Te5 (GST), are lossy in their crystalline phase, albeit transparent in the amorphous state. Moreover, electrically switching PCMs to intermediate states is a stochastic process, limiting programming accuracy. As a result, achieving both low-loss and deterministic multilevel operations with GST remains challenging. Although low-loss PCMs, such as Sb2S3 and Sb2Se3, have been discovered in recent years, they are much less technologically mature. We propose a design with multiple GST segments to overcome the challenge of deterministic multilevel operation. GST segments are individually controlled by interleaved silicon p++-doped-intrinsic-n++-doped diode heaters in a binary but reliable fashion, and multiple levels are encoded in their phase sequence. A 1×1 programmable unit with two unequal GST segments is experimentally demonstrated, showcasing four distinct operation levels and negligible thermal crosstalk with only one pair of metal contacts. We then extend the design to 1×2 and 2×2 programmable units. For the 2×2 programmable unit design, we propose a phase-detuned three-waveguide directional coupler structure to mitigate the absorption and radiation loss, showing <1.2 dB loss and three splitting ratios. We provide a new path toward low-loss and multilevel optical switches using lossy PCMs.
We demonstrated nonvolatile, electrically programmable, phase-only modulation of free-space infrared radiation in transmission based on low-loss phase change materials (PCMs) Sb2Se3. By coupling ultra-thin PCM to a high quality-factor (Q~406) diatomic metasurface, we demonstrated a phase-only modulation of ~0.25π (~0.2π) in simulation (experiment), ten times larger than without using the metasurface. The metasurface is robust against reversible switching over 1,000 times. Finally, we showed independent control of 17 meta-molecules, achieving ten deterministic resonance levels in a tunable notch filter with a maximum spectral shift of ~8nm. The independent control also allowed us to achieve varifocal lensing. This work paves way to a nonvolatile phase-only SLM.
Programmability is demanding in integrated photonics, while a suitable photonic platform is still lacking. It should have no static power, easy tuning knobs, high endurance, and many operation levels. We report a wide-bandgap PCM antimony sulfide (Sb2S3)-clad silicon photonic platform, based on which essential building blocks for programmable photonics are demonstrated, including micro-ring resonators, Mach-Zehnder Interferometers, and directional couplers. The fabricated devices simultaneously achieved low loss (<1.0 dB), high extinction ratio (>10 dB), high cyclability (>1,600 switching events), and 5-bit (32 operation levels) operation.
We demonstrate a nonvolatile electrically programmable phase-change silicon photonic switch and phase shifter leveraging a monolayer graphene heater with record-high programming energy efficiency (8.7±1.4 aJ/nm3) and endurance (> 1,000 cycles).
Phase-change materials (PCMs) integrated photonics are generating new paradigms, thanks to their zero static energy consumption, capability of switching reversibly, and drastic optical property contrast. However, electrically switching PCMs is inherently stochastic, hindering reliable multi-level or quasi-continuous operations. Here we propose that reliable quasi-continuous operation can be achieved in GST optical switches, where several GST patches are controlled in a binary fashion by interleaved PIN-diode doped silicon microheaters. We further experimentally demonstrate that the idea works in a tunable attenuator.
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