Explosive growth of datacenter traffic drives rapid scaling of optical interconnects architectures and technologies. We summarize the advancements in Intel’s heterogeneously integrated silicon photonics manufacturing platform enabling throughput scaling for IMDD and high-efficiency coherent links.

While compact and low-loss optical coupling to ultrahigh-quality-factor (Q) crystalline resonators is important for a wide range of applications, the major challenge for achieving this coupling stems from the relatively low refractive index of the crystalline resonator host material compared to those of the standard waveguide coupling materials. We report the first demonstration of a single-mode waveguide structure (prism-waveguide coupler) integrated on a low-loss compact silicon nitride platform resulting in low-loss and efficient coupling to magnesium fluoride crystalline resonators by achieving the phase-matched and the mode-matched evanescent wave coupling. The coupling is characterized with 1 dB loss at 1550 nm wavelength. We further present a photonic integrated chip containing a pair of waveguides successfully coupling light into and out of the resonator, demonstrating a planar-waveguide-coupled crystalline resonator with a loaded Q of 1.9 x 10(9). We assemble this waveguide-coupled resonator and a distributed- feedback-laser chip into a butterfly package to realize a miniature Kerr optical frequency comb source using self-injection locking of the distributed feedback laser to the waveguide-coupled crystalline resonator. (C) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

This paper reports design, fabrication, and experimental demonstration of a silicon nitride photonic integrated circuit (PIC). The PIC is capable of conducting one-dimensional interferometric imaging with twelve baselines near λ = 1100-1600 nm. The PIC consists of twelve waveguide pairs, each leading to a multi-mode interferometer (MMI) that forms broadband interference fringes or each corresponding pair of the waveguides. Then an 18 channel arrayed waveguide grating (AWG) separates the combined signal into 18 signals of different wavelengths. A total of 103 sets of fringes are collected by the detector array at the output of the PIC. We keep the optical path difference (OPD) of each interferometer baseline to within 1 µm to maximize the visibility of the interference measurement. We also constructed a testbed to utilize the PIC for two-dimension complex visibility measurement with various targets. The experiment shows reconstructed images in good agreement with theoretical predictions.

We design, fabricate and characterize first on-chip prism-like waveguide (prism-waveguide) coupler to high-Q (Q>1010) micro-resonator with record 1.1dB coupling loss at 1550nm and demonstrate an integrated optical frequency comb (OFC) generation unit based on this coupler.

We demonstrate hybrid integration of modified uni-traveling carrier photodiodes on a multi-layer silicon nitride platform using total internal reflection mirrors. Low-loss high-efficiency coupling of InGaAs detector on a silicon substrate has been realized.

The Lockheed Martin Advanced Technology Center and the University of California at Davis (UC Davis) has developed an interferometric imaging system based on photonic integrated circuits (PICs). This approach could enable a new hardware architecture with a 10x to 100x reduction in size and weight compared to traditional imaging systems, particularly targeted for space applications. The current PIC design consists of a three-layer system of waveguides, arrayed waveguide gratings (AWGs) and multi-mode interferometers (MMIs) that link 12 interferometric baselines to measure the phase and amplitude of the mutual intensity of an extended object. A series of lenslets couple light into 24 input waveguides on one edge of the PIC. On the opposite side there are 206 interferometer output ports that provide the fringe data for creating images. In this paper we will describe the photonic integrated circuit design and the testbed used to create the first images of extended scenes. We will also summarize the image reconstruction steps and present the final images.

This paper reports design, fabrication, and demonstration of a silica photonic integrated circuit (PIC) capable of conducting interferometric imaging with multiple baselines around λ = 1550 nm. The PIC consists of four sets of five waveguides (total of twenty waveguides), each leading to a three-band spectrometer (total of sixty waveguides), after which a tunable Mach-Zehnder interferometer (MZI) constructs interferograms from each pair of the waveguides. A total of thirty sets of interferograms (ten pairs of three spectral bands) is collected by the detector array at the output of the PIC. The optical path difference (OPD) of each interferometer baseline is kept to within 1 µm to maximize the visibility of the interference measurement. We constructed an experiment to utilize the two baselines for complex visibility measurement on a point source and a variable width slit. We used the point source to demonstrate near unity value of the PIC instrumental visibility, and used the variable slit to demonstrate visibility measurement for a simple extended object. The experimental result demonstrates the visibility of baseline 5 and 20 mm for a slit width of 0 to 500 µm in good agreement with theoretical predictions.

This paper demonstrates rapidly reconfigurable, high-fidelity optical arbitrary waveform generation (OAWG) in a heterogeneous photonic integrated circuit (PIC). The heterogeneous PIC combines advantages of high-speed indium phosphide (InP) modulators and low-loss, high-contrast silicon nitride (Si3N4) arrayed waveguide gratings (AWGs) so that high-fidelity optical waveform syntheses with rapid waveform updates are possible. The generated optical waveforms spanned a 160 GHz spectral bandwidth starting from an optical frequency comb consisting of eight comb lines separated by 20 GHz channel spacing. The Error Vector Magnitude (EVM) values of the generated waveforms were approximately 16.4%. The OAWG module can rapidly and arbitrarily reconfigure waveforms upon every pulse arriving at 2 ns repetition time. The result of this work indicates the feasibility of truly dynamic optical arbitrary waveform generation where the reconfiguration rate or the modulator bandwidth must exceed the channel spacing of the AWG and the optical frequency comb.

We demonstrate a three spectral band splitter that separates the wavelength bands of 1292nm, 1550nm and 1937nm. The device is fabricated using silicon nitride photonic integrated circuit platform. Optical characterization shows <;3 dB loss for the three channels, and 11 ~ 30 dB inter-channel crosstalk.

We present design, fabrication and characterization of a compact photonic integrated circuit consisting of tri-layer Si 3 N 4 platform including path-length-matching waveguides, multi-layer vertical couplers, arrayed waveguide gratings as demultiplexers, multimode interferometers and heater based phase tuner for long-baseline interferometric imaging.

We present a free-space coherent communication link employing orbital angular momentum (OAM) multiplexing using polarization diversified 2D-3D hybrid photonic integrated circuits (PICs). The PICs support multiplexing/demultiplexing of up to 15-OAM states with dual polarizations. We characterize the hybrid device, including phase errors and crosstalk performance. Then, we use two hybrid PICs for a free-space coherent communication link demonstration. We utilize polarization, frequency, quadrature, and space dimensions to achieve a 1.68-Tb/s link bandwidth and a 9.6-b/s/Hz spectral efficiency.

We demonstrate a hybrid integrated optical phased array (OPA) based on a 2D photonic integrated circuit and 3D waveguides. The 4×4 OPA supports 4.93° horizontal and vertical beam steering near 1550 nm with 7.1-dB loss.

Conventional elastic optical networking, EON, uses elasticity in two domains, time and frequency, to optimize utilization of optical network resources in the presence of fluctuating traffic demand and link quality. Currently, networking exploiting a third domain, space, is the focus of significant research efforts since space-division multiplexing, SDM, has the potential to substantially improve future network capacity and spectral efficiency. This article extends 2D-EON to include elasticity in all three domains: time, frequency, and space. We introduce enabling technologies, architectures, and algorithms for 3D-EONs. Based on sample network topologies, we investigate algorithms for routing, spectrum, spatial mode, and modulation format assignment - RSSMA. In particular, we investigate fragmentation-aware RSSMA and how the constraints in the formation of super-channels in MIMO-based SDM systems can impact the network performance in terms of blocking probability.

We demonstrate free-space space-division-multiplexing (SDM) with 15 orbital angular momentum (OAM) states using a three-dimensional (3D) photonic integrated circuit (PIC). The hybrid device consists of a silica planar lightwave circuit (PLC) coupled to a 3D waveguide circuit to multiplex/demultiplex OAM states. The low excess loss hybrid device is used in individual and two simultaneous OAM states multiplexing and demultiplexing link experiments with a 20 Gb/s, 1.67 b/s/Hz quadrature phase shift keyed (QPSK) signal, which shows error-free performance for 379,960 tested bits for all OAM states.

This paper discusses design, fabrication, and characterization of a 512 × 512 arrayed waveguide grating router (AWGR) with a channel spacing of 25 GHz. The dimensions of the AWGR is 16 mm × 11 mm and is fabricated on a 250 nm silicon-on-insulator platform. The measured channel crosstalk is approximately -4 dB without any compensation for the phase errors in the arrayed waveguides. The AWGR spectrum in the arrayed waveguide grating arms were characterized by using an optical vector network analyzer. Fabrication details of obtaining low loss silicon ridge waveguides are also discussed.

We demonstrate orbital angular momentum state conversion using two 3D photonic integrated circuits for free-space communication of 20-Gb/s QPSK signals. Different combinations of OAM states show error-free performance with 379,960 bits tested.

We present a silica photonic integrated circuit that includes the pathlength-matched photonic delay lines, spectral demultiplexers, phase modulators, and beam combiners needed for a thin form factor computational imaging system based on long baseline interferometry.

We present dual-polarization QPSK link transmission performance below the FEC limit with simultaneous transmission of three OAM states carrying 14×10-GBd WDM channels using silica 2D-3D hybrid integrated devices for OAM state multiplexing/demultiplexing capacity of 1.68 Tb/s.

We demonstrate a low-loss hybrid-integrated device based on a silica planar lightwave circuit (PLC) coupled to a 3-D photonic circuit that efficiently generates and multiplexes 15 optical orbital angular momentum (OAM) modes in free space.