Comparison and analysis of phase change materials-based reconfigurable silicon photonic directional couplers

Teo, Ting Yu; Krbal, Miloš; Mistrı́k, Jan; Přikryl, Jan; Lu, Li; Simpson, Robert E.

doi:10.1364/ome.447289

Cited by 50 publications

(49 citation statements)

References 39 publications

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“…The PCM-tuned Si waveguides used in the optical simulation were optimized in the transverse electric (TE) mode. The dimensions were chosen to ensure single mode operation. , In the simulation model, refractive indices of the Si waveguide, MoS 2 /WS 2 and GeTe layers were obtained from the literature. ,, The refractive index values can be found in Figure S6.To obtain the mode profile and overall effective index values of the waveguide, we solved Maxwell’s equations on the waveguide cross-section using the finite difference eigenmode solver from Lumerical Mode Solutions (LMS).…”

Section: Methodsmentioning

confidence: 99%

Low Energy Switching of Phase Change Materials Using a 2D Thermal Boundary Layer

Ning

Wang

Teo

et al. 2022

ACS Appl. Mater. Interfaces

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The switchable optical and electrical properties of phase change materials (PCMs) are finding new applications beyond data storage in reconfigurable photonic devices. However, high power heat pulses are needed to melt-quench the material from crystalline to amorphous. This is especially true in silicon photonics, where the high thermal conductivity of the waveguide material makes heating the PCM energy inefficient. Here, we improve the energy efficiency of the laser-induced phase transitions by inserting a layer of two-dimensional (2D) material, either MoS2 or WS2, between the silica or silicon substrate and the PCM. The 2D material reduces the required laser power by at least 40% during the amorphization (RESET) process, depending on the substrate. Thermal simulations confirm that both MoS2 and WS2 2D layers act as a thermal barrier, which efficiently confines energy within the PCM layer. Remarkably, the thermal insulation effect of the 2D layer is equivalent to a ∼100 nm layer of SiO2. The high thermal boundary resistance induced by the van der Waals (vdW)-bonded layers limits the thermal diffusion through the layer interface. Hence, 2D materials with stable vdW interfaces can be used to improve the thermal efficiency of PCM-tuned Si photonic devices. Furthermore, our waveguide simulations show that the 2D layer does not affect the propagating mode in the Si waveguide; thus, this simple additional thin film produces a substantial energy efficiency improvement without degrading the optical performance of the waveguide. Our findings pave the way for energy-efficient laser-induced structural phase transitions in PCM-based reconfigurable photonic devices.

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Section: Methodsmentioning

confidence: 99%

Low Energy Switching of Phase Change Materials Using a 2D Thermal Boundary Layer

Ning

Wang

Teo

et al. 2022

ACS Appl. Mater. Interfaces

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“…In all these devices, the central design principle is to change the coupling between waveguides by switching the PCM phase. The typical design procedure − ,, starts with picking a PCM thickness and performing optical mode simulations of the directional couplers using an electromagnetic field solver. One can then obtain the coupling length as L couple = λ/2( n e – n o ), with λ being wavelength and n e and n o being the effective index of the even and odd supermode of coupled waveguides, respectively.…”

Section: Challenges and Opportunitiesmentioning

confidence: 99%

“…One can then obtain the coupling length as L couple = λ/2( n e – n o ), with λ being wavelength and n e and n o being the effective index of the even and odd supermode of coupled waveguides, respectively. Then, by optimizing the waveguides gap and PCM thickness, a tunable beam splitter is designed …”

Section: Challenges and Opportunitiesmentioning

confidence: 99%

“…In contrast, the PCM device footprint was shown significantly reduced to ∼30 μm, 48 further improving the PIC's integration density. As conceptualized in Figure 3b, quasi-continuously programmable beam splitters are realized by placing low-loss PCM directly on one of two waveguides to form an asymmetric directional coupler, 102 and controlling with segmented heaters. With lossy PCMs, however, additional design considerations are necessary to mitigate material loss, such as adapting a three-waveguide geometry (Figure 3d), as explained earlier.…”

Section: Photonicsmentioning

confidence: 99%

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Opportunities and Challenges for Large-Scale Phase-Change Material Integrated Electro-Photonics

et al. 2022

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Programmable photonics have the potential to completely transform a range of emerging applications, including optical computing, optical signal processing, light detecting and ranging, and quantum applications. However, implementing energy-efficient and large-scale systems remains elusive because commonly used programmable photonic approaches are volatile and energy-hungry. Recent results on nonvolatile phase-change material (PCM) integrated photonics present a promising opportunity to create truly programmable photonics. The ability to drastically change the refractive index of the PCMs in a nonvolatile fashion allows creating programmable units with zero-static energy. By taking advantage of the electrical control, nonvolatile reconfiguration, and zero crosstalk between each unit, PCMs can enable extra large-scale integrated (ELSI) photonics. In this Perspective, we briefly review the recent progress in PCM photonics and discuss the challenges and limitations of this emerging technology. We argue that energy efficiency is a more critical parameter than the operating speed for programmable photonics, making PCMs an ideal candidate. This has the potential for a disruptive paradigm shift in the reconfigurable photonics research philosophy, as slow but energy-efficient and large index modulation can provide a better solution for ELSI photonics than fast but power-hungry, small index tuning methods. We also highlight the exciting opportunities to leverage wide bandgap PCMs for visible-wavelength applications, such as quantum photonics and optogenetics, and for rewritable photonic integrated circuits (PICs) using nanosecond pulsed lasers. The latter can dramatically reduce the fabrication cost of PICs and democratize the PIC manufacturing process for rapid prototyping.

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“…The PCM-tuned Si waveguides used in the optical simulation were optimized in the transverse electric (TE) mode. The dimensions were chosen to ensure single mode operation 51,52 . In the simulation model, refractive indices of the Si waveguide, MoS 2 /WS 2 and GeTe layers were obtained from literature 31,53,54 .…”

Section: Waveguide Simulationmentioning

confidence: 99%

Low energy switching of phase change materials using a 2D thermal boundary layer

Ning¹,

Wang²,

Teo³

et al. 2022

Preprint

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Comparison and analysis of phase change materials-based reconfigurable silicon photonic directional couplers

Cited by 50 publications

References 39 publications

Low Energy Switching of Phase Change Materials Using a 2D Thermal Boundary Layer

Low Energy Switching of Phase Change Materials Using a 2D Thermal Boundary Layer

Opportunities and Challenges for Large-Scale Phase-Change Material Integrated Electro-Photonics

Low energy switching of phase change materials using a 2D thermal boundary layer

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