Abstract Phase-change materials, demonstrating a rapid switching between two distinct states with a sharp contrast in electrical, optical or magnetic properties, are vital for modern photonic and electronic devices. To date, this effect is observed in chalcogenide compounds based on Se, Te or both, and most recently in stoichiometric Sb 2 S 3 composition. Yet, to achieve best integrability into modern photonics and electronics, the mixed S/Se/Te phase change medium is needed, which would allow a wide tuning range for such important physical properties as vitreous phase stability, radiation and photo-sensitivity, optical gap, electrical and thermal conductivity, non-linear optical effects, as well as the possibility of structural modification at nanoscale. In this work, a thermally-induced high-to-low resistivity switching below 200 °C is demonstrated in Sb-rich equichalcogenides (containing S, Se and Te in equal proportions). The nanoscale mechanism is associated with interchange between tetrahedral and octahedral coordination of Ge and Sb atoms, substitution of Te in the nearest Ge environment by S or Se, and Sb–Ge/Sb bonds formation upon further annealing. The material can be integrated into chalcogenide-based multifunctional platforms, neuromorphic computational systems, photonic devices and sensors.
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Are phase change materials ideal for programmable photonics?: opinion
The objective of this Opinion is to stimulate new research into materials that can meet the needs of tomorrow’s programmable photonics components. Herein, we argue that the inherent property portfolios of the common telluride phase change materials, which have been successfully applied in data storage technologies, are unsuitable for most emerging programmable photonics applications. We believe that newer PCMs with wider bandgaps, such as Sb2S3, Sb2Se3, and Ge2Sb2Se4Te (GSST), can be optimized to meet the demands of holographic displays, optical neural network memories, and beam steering devices.
more » « less- Award ID(s):
- 2132929
- NSF-PAR ID:
- 10369489
- Publisher / Repository:
- Optical Society of America
- Date Published:
- Journal Name:
- Optical Materials Express
- Volume:
- 12
- Issue:
- 6
- ISSN:
- 2159-3930
- Page Range / eLocation ID:
- Article No. 2368
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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In this work, we explore inverse designed reconfigurable digital metamaterial structures based on phase change material Sb2Se3for efficient and compact integrated nanophotonics. An exemplary design of a 1 × 2 optical switch consisting of a 3 µm x 3 µm pixelated domain is demonstrated. We show that: (i) direct optimization of a domain containing only Si and Sb2Se3pixels does not lead to a high extinction ratio between output ports in the amorphous state, which is owed to the small index contrast between Si and Sb2Se3in such a state. As a result, (ii) topology optimization, e.g., the addition of air pixels, is required to provide an initial asymmetry that aids the amorphous state's response. Furthermore, (iii) the combination of low loss and high refractive index change in Sb2Se3, which is unique among all phase change materials in the telecommunications 1550 nm band, translates into an excellent projected performance; the optimized device structure exhibits a low insertion loss (∼1.5 dB) and high extinction ratio (>18 dB) for both phase states.
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Abstract Scalable programmable photonic integrated circuits (PICs) can potentially transform the current state of classical and quantum optical information processing. However, traditional means of programming, including thermo-optic, free carrier dispersion, and Pockels effect result in either large device footprints or high static energy consumptions, significantly limiting their scalability. While chalcogenide-based non-volatile phase-change materials (PCMs) could mitigate these problems thanks to their strong index modulation and zero static power consumption, they often suffer from large absorptive loss, low cyclability, and lack of multilevel operation. Here, we report a wide-bandgap PCM antimony sulfide (Sb2S3)-clad silicon photonic platform simultaneously achieving low loss (<1.0 dB), high extinction ratio (>10 dB), high cyclability (>1600 switching events), and 5-bit operation. These Sb2S3-based devices are programmed via on-chip silicon PIN diode heaters within sub-ms timescale, with a programming energy density of
$$\sim 10\,{fJ}/n{m}^{3}$$ -
Non‐Volatile Reconfigurable Integrated Photonics Enabled by Broadband Low‐Loss Phase Change Materialmore » « less
Abstract Phase change materials (PCMs) have long been used as a storage medium in rewritable compact disk and later in random access memory. In recent years, integration of PCMs with nanophotonic structures has introduced a new paradigm for non‐volatile reconfigurable optics. However, the high loss of the archetypal PCM Ge2Sb2Te5in both visible and telecommunication wavelengths has fundamentally limited its applications. Sb2S3has recently emerged as a wide‐bandgap PCM with transparency windows ranging from 610 nm to near‐IR. In this paper, the strong optical phase modulation and low optical loss of Sb2S3are experimentally demonstrated for the first time in integrated photonic platforms at both 750 and 1550 nm. As opposed to silicon, the thermo‐optic coefficient of Sb2S3is shown to be negative, making the Sb2S3–Si hybrid platform less sensitive to thermal fluctuation. Finally, a Sb2S3integrated non‐volatile microring switch is demonstrated which can be tuned electrically between a high and low transmission state with a contrast over 30 dB. This work experimentally verifies prominent phase modification and low loss of Sb2S3in wavelength ranges relevant for both solid‐state quantum emitter and telecommunication, enabling potential applications such as optical field programmable gate array, post‐fabrication trimming, and large‐scale integrated quantum photonic network.
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Abstract The dearth of suitable materials significantly restricts the practical development of infrared (IR) laser systems with highly efficient and broadband tuning. Recently, γ‐NaAsSe2is reported, and it exhibits a large nonlinear second‐harmonic generation (SHG) coefficient of 590 pm V−1at 2 µm. However, the crystal growth of γ‐NaAsSe2is challenging because it undergoes a phase transition to centrosymmetric δ‐NaAsSe2. Herein, the stabilization of non‐centrosymmetric γ‐NaAsSe2by doping the As site with Sb, which results in γ‐NaAs0.95Sb0.05Se2is reported. The congruent melting behavior is confirmed by differential thermal analysis with a melting temperature of 450 °C and crystallization temperature of 415 °C. Single crystals with dimensions of 3 mm × 2 mm are successfully obtained via zone refining and the Bridgman method. The purification of the material plays a significant role in crystal growth and results in a bandgap of 1.78 eV and thermal conductivity of 0.79 Wm−1K−1. The single‐crystal SHG coefficient of γ‐NaAs0.95Sb0.05Se2exhibits an enormous value of |
d 11| = 648 ± 74 pm V−1, which is comparable to that of γ‐NaAsSe2and ≈20× larger than that of AgGaSe2. The bandgap of γ‐NaAs0.95Sb0.05Se2(1.78 eV) is similar to that of AgGaSe2, thus rendering it highly attractive as a high‐performing nonlinear optical material.
