&lt;title&gt;Variation of the complex refractive indices with Sb-addition in Ge-Sb-Te alloy and their wavelength dependence&lt;/title&gt;

Kim, Sang-Youl; Kim, Sang J.; Seo, Hanbyul; Kim, Myong R.

doi:10.1117/12.327935

Cited by 30 publications

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“…For use with the FDTD method the refractive index profile is modeled as a multi-pole Lorentzian material over the wavelength range of interest around 1550nm [19]. In Fig.2(a) the markers denote the data taken from [20], while the solid lines represent the multiLoretzian fit in good agreement with the measured values. Knowing the roundtrip loss dB α in units of dB/cm, the optical quality factor can then be estimated as dB g n e Q λα π / 2 log 10 10 ⋅ = [21].…”

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confidence: 76%

Photonic non-volatile memories using phase change materials

Pernice¹,

Bhaskaran²

2012

Applied Physics Letters

150

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We propose an all-photonic, non-volatile memory and processing element based on phase-change thin-films deposited onto nanophotonic waveguides. Using photonic microring resonators partially covered with Ge 2 Sb 2 Te 5 (GST) multi-level memory operation in integrated photonic circuits can be achieved. GST provides a dramatic change in refractive index upon transition from the amorphous to crystalline state, which is exploited to reversibly control both the extinction ratio and resonance wavelength of the microcavity with an additional gating port in analogy to optical transistors. Our analysis shows excellent sensitivity to the degree of crystallization inside the GST, thus providing the basis for non-von Neuman neuromorphic computing.The ability to write, store and retrieve data is at the very heart of information processing. Various techniques are employed to efficiently cope with the vast spread of speed and long term storage needs. In particular Phase Change Memories (PCMs), promise to revolutionize the field of information processing by bridging the gap between the short-term, but very quick operation of on-chip memories and the long-term, but relatively slow storage systems such as solid-state devices and hard-drives [1][2][3]. Not only can phase change materials switch in a matter of picoseconds [4-6], they are also able to retain information for very long periods of time [2,7]. In addition, they scale extremely well to the nanoscale, with present-day demonstrations of 6nm cells employing electrical switching [7,8]. Specifically Ge 2 Sb 2 Te 5 (GST) is the most commonly used alloy for such applications. By reversibly transforming the crystalline structure between amorphous and crystalline states using electrical pulses, the resistive properties of the thin film can be varied by several orders of magnitude [9]. PCMs also demonstrate a large difference in reflectivity upon phase-transition, an effect that has led to their commercial use in optical storage discs, such as DVDs and Blue-Ray discs [10].Herein, we propose a chalcogenide-based integrated photonic memory element, with the ability for sub-nanosecond reading and writing, while still retaining data for several years. We analyze the photonic architecture as illustrated in Fig.1(a), which comprises a microring resonator coupled to nanophotonic waveguides. In contrast to photonic memories and mechanical resonators [11], the photonic circuit allows for static tunability which is maintained when the control light has been switched off. We base our analysis on silicon nitride-on-insulator substrates for broadband optical applications. Silicon nitride can be used to fabricate high-quality nanophotonic components for both telecoms and visible applications [12,13]. The feeding waveguide is optimized for single mode operation at 1550nm input wavelength. Inside the ring resonator a small region of the waveguide is suspended similar to waveguides used for nanomechanical sensing [14] and opto-mechanical operation [15]. A thin film of phase change material (GST) is...

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confidence: 76%

Photonic non-volatile memories using phase change materials

Pernice¹,

Bhaskaran²

2012

Applied Physics Letters

150

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“…The orange part represents GST, whose thickness was 50nm and the sidewall is about half of the thickness according to our experience of the fabrication process. The complex refractive indices for amorphous GST (a_GST) and crystalline GST (c_GST) are 4.6+0.18i and 7.2+1.9i using spectroscopic ellipsometry [22]. The E-field intensity of the optical mode profiles of ridge and slot-ridge waveguides are shown in Fig.…”

Section: Device Conceptmentioning

confidence: 99%

On-Chip Photonic Synapses Based on Slot-Ridge Waveguides With PCMs For In-Memory Computing

et al. 2021

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Because of the von Neumann bottleneck, neuromorphic networks aimed at in-memory computing, such as brains, are extensively studied. As artificial synapses are essential in neuromorphic networks, a photonic synapse based on slot-ridge waveguides with nonvolatile phase-change materials (PCMs) was proposed and demonstrated in an SOI platform with standard complementary metal-oxide-semiconductor (CMOS) process for a larger weight dynamic range. The change of the optical transmission spectrum of our photonic synapses was about 3.5dB higher than that of primitive synapses, which meant large weight dynamic range and more weight values. A 90.7% recognition accuracy based on our photonic synapses, which was 2.6% higher than that of primitive synapses, was realized for the MNIST handwritten digits recognition task performed by a three-layer perceptron. Besides, because of the nonvolatile nature of PCMs, the weights achieved by our photonic synapses can be stored in situ ensuring a lower consumption in in-memory computing. This framework can potentially achieve a more efficient in-memory computing neuromorphic network in silicon photonics.

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“…PCMs have the ability to dramatically and reversibility change their complex refractive index between two stable phases, amorphous and crystalline, based on the application of an optical or electrical energy pulse. Importantly, the difference in the real part of the refractive index between the two states (Δn) is as high as 1.5/2 while the absorption coefficient (Δk) can change by more than 3 upon switching …”

Section: Background and Objectivesmentioning

confidence: 99%

“…Importantly, the difference in the real part of the refractive index between the two states (Δn) is as high as 1.5/2 while the absorption coefficient (Δk) can change by more than 3 upon switching. 2 We recently demonstrated the feasibility of a low-power, high color reflective display based on a new optical modulation mechanism-reversible PCM crystallization in an ultra-thin film stack-which is entirely new to the field of displays. [3][4][5] Our simulated performance indicates that a display utilizing this effect can be designed to provide white state luminance reflectivity of over 50% and a color gamut between 40% and 80% of sRGB depending on fabrication complexity.…”

Section: Background and Objectivesmentioning

confidence: 99%

Solid‐state reflective displays (SRD^®) for video‐rate, full color, outdoor readable displays

et al. 2018

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<title>Variation of the complex refractive indices with Sb-addition in Ge-Sb-Te alloy and their wavelength dependence</title>

Cited by 30 publications

References 0 publications

Photonic non-volatile memories using phase change materials

Photonic non-volatile memories using phase change materials

On-Chip Photonic Synapses Based on Slot-Ridge Waveguides With PCMs For In-Memory Computing

Solid‐state reflective displays (SRD^®) for video‐rate, full color, outdoor readable displays

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<title>Variation of the complex refractive indices with Sb-addition in Ge-Sb-Te alloy and their wavelength dependence</title>

Cited by 30 publications

References 0 publications

Photonic non-volatile memories using phase change materials

Photonic non-volatile memories using phase change materials

On-Chip Photonic Synapses Based on Slot-Ridge Waveguides With PCMs For In-Memory Computing

Solid‐state reflective displays (SRD®) for video‐rate, full color, outdoor readable displays

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Product

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Solid‐state reflective displays (SRD^®) for video‐rate, full color, outdoor readable displays