Quantum computing (QC) is theorized to solve certain important problems much faster than classical computers. The current state of QC, the noisy intermediate-scale quantum (NISQ) era, is limited in the scope of problems it can solve, largely due to the quantity of reliable qubits available to universal quantum operations. And while all available quantum computing systems have their advantages, ion-based systems have been shown to be a reliable option with low infidelity and a capability for universal gating procedure. These advantages are dependent on achieving low crosstalk when addressing ions, a vital challenge for this QC system, particularly when using only bulk optic systems. Here we show a microfabricated planar waveguide which can selectively interact in free space with 8 trapped Ba+ ions. This performance meets or exceeds that of similar waveguides couple to trapped ion systems and shows a reliable method to selectively interact with ions bound by a Paul Trap using imaged waveguide outputs.
The explosive growth of data-centric artificial intelligence applications calls for the next generation of optical interconnects for future hyperscale data centers and high-performance computing (HPC) systems. To unleash the full potential of dense wavelength-division multiplexing, we present the design and exploration of a novel transceiver architecture based on silicon photonic micro-resonators featuring a broadband Kerr frequency comb source and fabrication-robust (de-)interleaving structures. In contrast to the traditional single-bus architecture, our architecture de-interleaves the comb onto multiple buses before traversing separate banks of cascaded resonant modulators/filters, effectively doubling the channel spacing with each stage of de-interleaving. With a closed-form free spectral range (FSR) engineering technique guiding the micro-resonator design, the architecture is scalable toward hundreds of parallel channels—spanning much wider than the resonator FSRs—with minimal crosstalk penalty and thermal tuning overhead. This unique architecture, designed with co-packageability in mind, thus enables a multi-Tbps aggregated data rate with moderate per-channel data rates, paving the way for sub-pJ/b ultra-high-bandwidth chip-to-chip connectivity in future data centers and HPC systems.
While the high index contrast between silicon and silicon dioxide in the silicon-on-insulator photonics platform permits unprecedented device density, it also leads to high sensitivity to fabrication variations. In silicon microring and microdisk resonator devices, fabrication variations can substantially change the target resonance wavelength. Silicon’s high thermo-optic coefficient allows for correction of these fabrication variations and stabilization of the device resonant wavelength through thermal tuning. Metal and doped silicon integrated heaters are commonly used to perform this tuning and have become an essential feature of silicon microring and microdisk modulators. Metal heaters are typically placed in a layer above the silicon devices, while doped silicon heaters are placed in the same silicon waveguide layer, adjacent to the devices. The advantage of doped silicon heaters over metal heaters is due to proximity of the heater to the optical device, leading to greater efficiencies. However, for active devices using p-n junctions such as modulators, parasitic junctions can form between the doped heater and the modulator junctions, resulting in highly unstable and substandard device performance. Here, we present a detailed simulation framework for heater design in resonant silicon microdisk modulators, supported by experimentally measured device performance, which emphasizes tuning efficiency while eliminating parasitic diode formation. Simulations were conducted in Ansys Lumerical HEAT, CHARGE, and MODE to model parasitic junction behavior between the heater and modulator, in addition to the heater’s thermal response and its effect on the resonant wavelength of the microdisk.
We demonstrate an optimized silicon photonic link architecture using components from the AIM PDK that achieves an ultra-low sub-pJ/bit power consumption with an aggregate bandwidth of 480 Gb/s. At the transmitter, micro-disk modulators are cascaded along a bus waveguide to select and modulate wavelength-division multiplexed (WDM) channels. At the receiver, micro-ring resonator (MRR) filters are thermally tuned to match the corresponding disks to select from the multiplexed channels. This link architecture yields an ultra-small footprint compared to Mach-Zehnder designs, improving the system scalability and bandwidth density. Additionally, using micro-resonators to select and drop the desired wavelengths from a single bus waveguide allows for straightforward integration with a frequency comb source. The energy performance of the design is optimized through sweeping over three key parameters: (i) optical power per channel, (ii) channel count, and (iii) bitrate. These parameters are the dominant sources for the crosstalk and power penalty in the link design. We identify ideal points in the design space which minimize the energy per bit while staying below the desired bit error rate (BER) of 10-12 and maintaining a realistic aggregate bandwidth. Simulations in the Synopsys OptSim environment using the AIM PDK v2.5a models confirm the functionality of the system with a BER < 10-12, acceptable for both high performance computing (HPC) and data center (DC) applications. Furthermore, optimizing the link energy consumption in the AIM PDK provides a clear path towards low-cost and high-yield fabrication suitable for application in HPC and DC systems.
NASA is working with US industry and academia to develop Photonic Integrated Circuits (PICs) for: (1) Sensors (2) Analog RF applications (3) Computing and free space communications. The PICs provide reduced size, weight, and power that is critical for space-based systems. We describe recent breakthrough 3D monolithic integration of photonic structures, particularly high-speed graphene-silicon devices on CMOS electronics to create CMOS-compatible highbandwidth transceivers for ultra-low power Terabit-scale optical communications. An integrated graphene electro-optic modulator has been demonstrated with a bandwidth of 30 GHz. Graphene microring modulators are especially attractive for dense wavelength division multiplexed (DWDM) systems. For space-based optical communication and ranging we have demonstrated generating a variable number of channels from a single laser using breadboard components, using a single-sideband carrier-suppressed (SSBCS) modulator driven by an externally-supplied RF tone (arbitrary RF frequency), a tunable optical bandpass filter, and an optical amplifier which are placed in a loop. We developed a Return--to-Zero (RZ) Differential Phase Shift Keying (DPSK) laser transmitter PIC using an InP technology platform that includes a tunable laser, a Semiconductor Optical Amplifier (SOA), high-speed Mach-Zehnder Modulator (MZM), and an electroabsorption (EAM) modulator. A Silicon Nitride (SiN) platform integrated photonic circuit suitable for a spectrally pure chip-scale tunable opto-electronic RF oscillator (OEO) that can operate as a flywheel in high precision optical clock modules, as well as radio astronomy, spectroscopy, and local oscillator in radar and communications systems is needed. We have demonstrated a low noise optical frequency combs generation from a small OEO prototypes containing very low loss (~1 dB) waveguide couplers of various shapes and sizes integrated with an ultrahigh-Q MgF2 resonators. An innovative miniaturized lab-on-a-chip device is being developed to directly monitor astronaut health during missions using ~3 drops of body fluid sample like blood, urine, and potentially other body fluids like saliva, sweat or tears. The first-generation system comprises a miniaturized biosensor based on PICs (including Vertical Cavity Surface Emitting Laser – VCSEL, photodetector and optical filters and biochemical assay that generates a fluorescent optical signal change in response to the target analyte.
Ring resonators are used as photon pair sources by taking advantage of the materials second or third order non- linearities through the processes of spontaneous parametric downconversion and spontaneous four wave mixing respectively. Two materials of interest for these applications are silicon for the infrared and aluminum nitride for the ultraviolet through the infrared. When fabricated into ring type sources they are capable of producing pairs of indistinguishable photons but typically suffer from an effective 50% loss. By slightly decoupling the input waveguide from the ring, the drop port coincidence ratio can be significantly increased with the trade-off being that the pump is less efficiently coupled into the ring. Ring resonators with this design have been demonstrated having coincidence ratios of 96% but requiring a factor of ~10 increase in the pump power. Through the modification of the coupling design that relies on additional spectral dependence, it is possible to achieve similar coincidence ratios without the increased pumping requirement. This can be achieved by coupling the input waveguide to the ring multiple times, thus creating a Mach-Zehnder interferometer. This coupler design can be used on both sides of the ring resonator so that resonances supported by one of the couplers are suppressed by the other. This is the ideal configuration for a photon-pair source as it can only support the pump photons at the input side while only allowing the generated photons to leave through the output side. Recently, this device has been realized with preliminary results exhibiting the desired spectral dependence and with a coincidence ratio as high as ~ 97% while allowing the pump to be nearly critically coupled to the ring. The demonstrated near unity coincidence ratio infers a near maximal heralding efficiency from the fabricated device. This device has the potential to greatly improve the scalability and performance of quantum computing and communication systems.
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