Optical switching at 1.55 <i>μ</i>m in silicon racetrack resonators using phase change materials

Rudé, Miquel; Pello, Josselin; Simpson, Robert E.; Osmond, Johann; Roelkens, Günther; Tol, J.J.G.M. van der; Pruneri, Valerio

doi:10.1063/1.4824714

Cited by 205 publications

(146 citation statements)

References 29 publications

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“…Re-crystallization is achieved by heating above the glass transition temperature and then slowly cooling 5 . The crystallographic switching process is accompanied by an unusually large change in the optical and electronic properties of the material and makes PCMs important for many applications, such as optical data storage 5 , nonvolatile memories 6 and photonics 7,8 . The large optical contrast is attributed to the so-called resonant bonding in the crystalline phase 9,10 .…”

Section: Introductionmentioning

confidence: 99%

Ultrafast optical response of the amorphous and crystalline states of the phase change materialGe2Sb2Te5

et al. 2016

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We examine the ultrafast optical response of the crystalline and amorphous phases of the phase change material Ge2Sb2Te5 below the phase transformation threshold. Simultaneous measurement of the transmissivity and reflectivity of thin film samples yields the time-dependent evolution of the dielectric function for both phases. We then identify how lattice motion and electronic excitation manifest in the dielectric response. The dielectric response of both phases is large but markedly different. At 800 nm, the changes in amorphous GST are well described by the Drude response of the generated photo-carriers, whereas the crystalline phase is better described by the depopulation of resonant bonds. We find that the generated coherent phonons have a greater influence in the amorphous phase than the crystalline phase. Furthermore, coherent phonons do not influence resonant bonding. For fluences up to 50% of the transformation threshold, the structure does not exhibit bond softening in either phase, enabling large changes of the optical properties without structural modification.

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Section: Introductionmentioning

confidence: 99%

Ultrafast optical response of the amorphous and crystalline states of the phase change materialGe2Sb2Te5

et al. 2016

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“…These beneficial properties of PCMs have already led to prominent commercial applications in optical data storage such as rewritable optical discs (in DVD and Blu-ray formats) 21 and more recently for use in optoelectronic modulation and display applications in the visible spectrum 22 . -3-Many PCMs show significant change in refractive index in the visible and even larger changes in the near-infrared wavelength regime, which is the spectral region of choice for telecommunication applications [23][24][25][26] . Here, by using such nanoscale PCMs embedded in nanophotonic circuits, we demonstrate that fast and repeatable all-optical, multi-level, multi-bit, nonvolatile memory operations, with wavelength division multiplexed (WDM) access, can be achieved on a chip at telecommunications wavelengths compatible with on-chip optical interconnects.…”

mentioning

confidence: 99%

Integrated all-photonic non-volatile multi-level memory

et al. 2015

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Rios, Stegmaier et al., Integratable all-photonic nonvolatile multi-level memory Integratable all-photonic nonvolatile multi-level memoryWe show that individual memory elements can be addressed using a wavelength multiplexing scheme. Our multi-level, multi-bit devices provide a pathway towards eliminating the von-Neumann bottleneck and portend a new paradigm in all-photonic memory and non-conventional computing.* These authors contributed equally.-2-The advent of photonic technologies, in particular in the area of optical signaling, coupled with advances made in nanofabrication capabilities has created a growing need for practical allphotonic memories 3,[7][8][9][10] . Such memories are essential to supercharge computational performance in serial computers by speeding up the von-Neumann bottleneck, i.e. the information traffic jam between the processor and the memory. This bottleneck limits the speed of almost all processors today; it has already led to the introduction of multicore processor architectures and drives the search for viable on-chip optical interconnects. However, shuttling information optically from the processor to electronic memories is presently not efficient because electrical signals have to be converted to optical ones and vice-versa. Instead, information transfer and storage exclusively by optical means is highly desirable because of the inherently large bandwidth 1,3 , low residual cross-talk and high speed of optical information transfer. On a chip this has been challenging to achieve because practical photonic memories would need to retain information for long periods of time and require full-integration with the ancillary electronic circuitry, thus requiring compatibility with semiconductor processing 11.Ideal candidates for all-optical memories are phase-change materials (PCMs), already the subject of intense research and development over the last decade, but in the context of electronic memories [12][13][14] . A striking and functional feature of these materials is the high contrast between the crystalline and amorphous phase of both their electrical and optical properties 15,16 . In particular, chalcogenide-based PCMs have the ability to switch between these two states in response to appropriate heat stimuli (crystallization) or melt-quenching processes down to nanoscale cell sizes, which enables dense packaging and low-power memory switching. In our devices, data is stored in a nanoscale GST cell placed directly on top of a nanophotonic waveguide. Both writing into the memory cell and read-out of the stored information is carried out via evanescent coupling to the phase-change material and is thus not subject to the diffraction limit; because this is done directly within the waveguide using nanosecond optical pulses, our approach provides a promising route towards fast all-optical data storage in photonic circuits.The geometry of our memory cell and the operating principle is shown schematically in Fig. 1a. We store information in the GST (yellow region) by employing evanescent coup...

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“…The wavelength of operation can be changed by several nanometers without injuring the EO switching. This improves upon some resonant prior art [1] where a racetrack resonator had PCM cladding perturbation. Most of the prior art uses optical control, which means that a "shortwave" optical pump was shone upon the PCM cladding to trigger switching.…”

Section: Comparison With the Prior Artmentioning

confidence: 77%

Electro-optical phase-change 2 × 2 switching using three- and four-waveguide directional couplers

Liang

Soref

et al. 2015

Appl. Opt.

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Theoretical modeling and numerical simulation have been performed at λ=2100 nm on silicon-on-insulator channel-waveguide directional couplers in which the outer two Si waveguides are passive and the central waveguide(s) are electro-optical (EO) "islands." The EO channel(s) utilize a 10 nm layer of Ge2Sb2Te5 phase-change-material sited at midlevel of a doped Si channel. A voltage-driven phase change produces a large change in the effective index of the TE(o) and TM(o) modes, thereby inducing crossbar 2×2 switching. A mode-matching method is employed to estimate EO switching performance in the limit of strong interguide coupling. Low-loss switching is predicted for cross-to-bar and bar-to-cross coupling lengths. These "self-holding" switches had active lengths of 500-1000 μm, which are shorter than those in couplers relying upon free-carrier injection. The four-waveguide devices had lower cross talk but higher loss than the three-waveguide devices. For the crystalline phase we sometimes used an active length that was smaller than that for the amorphous phase.

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Optical switching at 1.55 μm in silicon racetrack resonators using phase change materials

Cited by 205 publications

References 29 publications

Ultrafast optical response of the amorphous and crystalline states of the phase change materialGe2Sb2Te5

Ultrafast optical response of the amorphous and crystalline states of the phase change materialGe2Sb2Te5

Integrated all-photonic non-volatile multi-level memory

Electro-optical phase-change 2 × 2 switching using three- and four-waveguide directional couplers

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