Non-volatile electrically programmable integrated photonics with a 5-bit operation.

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.

Compact nonvolatile polarization switch using an asymmetric SbSe-loaded silicon waveguide.

We propose and simulate a compact (∼29.5 µm-long) nonvolatile polarization switch based on an asymmetric SbSe-clad silicon photonic waveguide. The polarization state is switched between TM and TE mode by modifying the phase of nonvolatile SbSe between amorphous and crystalline.

Ultra-low-energy programmable non-volatile silicon photonics based on phase-change materials with graphene heaters.

Silicon photonics is evolving from laboratory research to real-world applications with the potential to transform many technologies, including optical neural networks and quantum information processing. A key element for these applications is a reconfigurable switch operating at ultra-low programming energy-a challenging proposition for traditional thermo-optic or free carrier switches. Recent advances in non-volatile programmable silicon photonics based on phase-change materials (PCMs) provide an attractive solution to energy-efficient photonic switches with zero static power, but the programming energy density remains high (hundreds of attojoules per cubic nanometre).

High-Q, submicron-confined chalcogenide microring resonators.

We demonstrate high quality (Q) factor microring resonators in high index-contrast GeSbSe chalcogenide glass waveguides using electron-beam lithography followed by plasma dry etching. A microring resonator with a radius of 90 μm shows an intrinsic Q factor of 4.1 × 10 in the telecom band.

High quality, high index-contrast chalcogenide microdisk resonators.

We demonstrate the high quality (Q) factor microdisk resonators in high index-contrast chalcogenide glass (ChG) film GeSbSe using electron-beam lithography followed by plasma dry etching. High confinement, low-loss, and single-point-coupled microdisk resonators with a loaded Q factor of 5×10 are measured. We also present pulley-coupled microdisk resonators for relaxing the requirements on the coupling gap.

Ultra-low-power nonvolatile integrated photonic switches and modulators based on nanogap-enhanced phase-change waveguides.

We propose a nanogap-enhanced phase-change waveguide with silicon PIN heaters. Thanks to the enhanced light-matter interaction in the nanogap, the proposed structure exhibits strong attenuation (Δα = ∼35 dB/µm) and optical phase (Δn = ∼1.2) modulation at λ = 1550 nm when achieving complete phase transitions.

Nonvolatile Electrically Reconfigurable Integrated Photonic Switch Enabled by a Silicon PIN Diode Heater.

Reconfigurability of photonic integrated circuits (PICs) has become increasingly important due to the growing demands for electronic-photonic systems on a chip driven by emerging applications, including neuromorphic computing, quantum information, and microwave photonics. Success in these fields usually requires highly scalable photonic switching units as essential building blocks. Current photonic switches, however, mainly rely on materials with weak, volatile thermo-optic or electro-optic modulation effects, resulting in large footprints and high energy consumption.

Modeling Electrical Switching of Nonvolatile Phase-Change Integrated Nanophotonic Structures with Graphene Heaters.

Progress in integrated nanophotonics has enabled large-scale programmable photonic integrated circuits (PICs) for general-purpose electronic-photonic systems on a chip. Relying on the weak, volatile thermo-optic, or electro-optic effects, such systems usually exhibit limited reconfigurability along with high-energy consumption and large footprints. These challenges can be addressed by resorting to chalcogenide phase-change materials (PCMs) such as GeSbTe (GST) that provide a substantial optical contrast in a self-holding fashion upon phase transitions.

Ultra-low mode volume on-substrate silicon nanobeam cavity.

We design and fabricate an on-substrate bowtie photonic crystal (PhC) cavity in silicon. By optimizing the bowtie shapes in the unit cells of the PhC cavity, the maximum of the electric field can be highly confined in the bowtie tips. Due to such confinement, an ultra-low mode volume of ∼0.

Large thermal tuning of a polymer-embedded silicon nitride nanobeam cavity.

Tunable silicon nitride nanophotonic resonators are a critical building block for integrated photonic systems in the visible wavelength range. We experimentally demonstrate a thermally tunable polymer-embedded silicon nitride nanobeam cavity with a tuning efficiency of 44 pm/°C and 0.13 nm/mW in the near-visible wavelength range.

Multi-slot photonic crystal cavities for high-sensitivity refractive index sensing.

We present the design, fabrication, and characterization of a multi-slot photonic crystal (PhC) cavity sensor on the silicon-on-insulator platform. By optimizing the structure of the PhC cavity, most of the light can be distributed in the lower index region; thus, the sensitivity can be dramatically improved. By exposing the cavities to different mass concentrations of NaCl solutions, we obtained that the wavelength shift per refractive index unit (RIU) for the sensor is 586 nm/RIU, which is one of the highest sensitivities achieved in a non-suspended cavity.

Ultrathin van der Waals Metalenses.

Ultrathin and flat optical lenses are essential for modern optical imaging, spectroscopy, and energy harvesting. Dielectric metasurfaces comprising nanoscale quasi-periodic resonator arrays are promising for such applications, as they can tailor the phase, amplitude, and polarization of light at subwavelength resolution, enabling multifunctional optical elements. To achieve 2π phase coverage, however, most dielectric metalenses need a thickness comparable to the wavelength, requiring the fabrication of high-aspect-ratio scattering elements.

Nanocavity Integrated van der Waals Heterostructure Light-Emitting Tunneling Diode.

Developing a nanoscale, integrable, and electrically pumped single mode light source is an essential step toward on-chip optical information technologies and sensors. Here, we demonstrate nanocavity enhanced electroluminescence in van der Waals heterostructures (vdWhs) at room temperature. The vertically assembled light-emitting device uses graphene/boron nitride as top and bottom tunneling contacts and monolayer WSe as an active light emitter.

Tunable pattern-free graphene nanoplasmonic waveguides on trenched silicon substrate.

Graphene has emerged as a promising material for active plasmonic devices in the mid-infrared (MIR) region owing to its fast tunability, strong mode confinement, and long-lived collective excitation. In order to realize on-chip graphene plasmonics, several types of graphene plasmonic waveguides (GPWGs) have been investigated and most of them are with graphene ribbons suffering from the pattern-caused edge effect. Here we propose a novel nanoplasmonic waveguide with a pattern-free graphene monolayer on the top of a nano-trench.

Local and nonlocal optically induced transparency effects in graphene-silicon hybrid nanophotonic integrated circuits.

Graphene is well-known as a two-dimensional sheet of carbon atoms arrayed in a honeycomb structure. It has some unique and fascinating properties, which are useful for realizing many optoelectronic devices and applications, including transistors, photodetectors, solar cells, and modulators. To enhance light-graphene interactions and take advantage of its properties, a promising approach is to combine a graphene sheet with optical waveguides, such as silicon nanophotonic wires considered in this paper.

Suspended ultra-small disk resonator on silicon for optical sensing.

An ultra-small disk resonator consisting of a suspended silicon disk with a submicron bending radius sitting on an SiO(2) pedestal is demonstrated experimentally. An asymmetrical suspended rib waveguide is integrated as the access waveguide for the suspended submicron disk resonator, which is used to realize an ultra-small optical sensor with an improved sensitivity due to the enhanced evanescent field interaction with the analyte. The present optical sensor also has a large measurement range because of the ultra-large free-spectral range of the submicron-disk resonator.

Slotted photonic crystal nanobeam cavity with parabolic modulated width stack for refractive index sensing.

We present the design, fabrication, and the characterization of high-Q slotted 1D photonic crystal (PhC) cavities with parabolic-width stack. Their peculiar geometry enables the location of the resonating mode close to the air-band. The majority of optical field distributes in the slotted low-index area and the light matter interaction with the analytes has been enhanced.