Silicon photonics has emerged as the leading candidate for implementing ultralow power wavelength–division–multiplexed communication networks in high-performance computers, yet current components (lasers, modulators, filters and detectors) consume too much power for the high-speed femtojoule-class links that ultimately will be required. Here we demonstrate and characterize the first modulator to achieve simultaneous high-speed (25 Gb s−1), low-voltage (0.5 VPP) and efficient 0.9 fJ per bit error-free operation. This low-energy high-speed operation is enabled by a record electro-optic response, obtained in a vertical p–n junction device that at 250 pm V−1 (30 GHz V−1) is up to 10 times larger than prior demonstrations. In addition, this record electro-optic response is used to compensate for thermal drift over a 7.5 °C temperature range with little additional energy consumption (0.24 fJ per bit for a total energy consumption below 1.03 J per bit). The combined results of highly efficient modulation and electro-optic thermal compensation represent a new paradigm in modulator development and a major step towards single-digit femtojoule-class communications.

Accurate conversion of wideband multi-GHz analog signals into the digital domain has long been a target of analog-to-digital converter (ADC) developers, driven by applications in radar systems, software radio, medical imaging, and communication systems. Aperture jitter has been a major bottleneck on the way towards higher speeds and better accuracy. Photonic ADCs, which perform sampling using ultra-stable optical pulse trains generated by mode-locked lasers, have been investigated for many years as a promising approach to overcome the jitter problem and bring ADC performance to new levels. This work demonstrates that the photonic approach can deliver on its promise by digitizing a 41 GHz signal with 7.0 effective bits using a photonic ADC built from discrete components. This accuracy corresponds to a timing jitter of 15 fs -a 4-5 times improvement over the performance of the best electronic ADCs which exist today. On the way towards an integrated photonic ADC, a silicon photonic chip with core photonic components was fabricated and used to digitize a 10 GHz signal with 3.5 effective bits. In these experiments, two wavelength channels were implemented, providing the overall sampling rate of 2.1 GSa/s. To show that photonic ADCs with larger channel counts are possible, a dual 20-channel silicon filter bank has been demonstrated. 289-296 (1992). 11. J. Kim, J. Chen, J. Cox, and F. X. Kärtner, "Attosecond-resolution timing jitter characterization of free-running mode-locked lasers using balanced optical cross-correlation," Opt. Lett. microwave signals at 40-GHz with higher than 7-ENOB resolution," Opt. ©2012 Optical Society of America

Integrated photonics will play a key role in quantum systems as they grow from few-qubit prototypes to tens of thousands of qubits. The underlying optical quantum technologies can only be realized through the integration of these components onto quantum photonic integrated circuits (QPICs) with accompanying electronics. In the last decade, remarkable advances in quantum photonic integration have enabled table-top experiments to be scaled down to prototype chips with improvements in efficiency, robustness, and key performance metrics. These advances have enabled integrated quantum photonic technologies combining up to 650 optical and electrical components onto a single chip that are capable of programmable quantum information processing, chip-to-chip networking, hybrid quantum system integration, and high-speed communications. In this roadmap article, we highlight the status, current and future challenges, and emerging technologies in several key research areas in integrated quantum photonics, including photonic platforms, quantum and classical light sources, quantum frequency conversion, integrated detectors, and applications in computing, communications, and sensing. With advances in materials, photonic design architectures, fabrication and integration processes, packaging, and testing and benchmarking, in the next decade we can expect a transition from single- and few-function prototypes to large-scale integration of multi-functional and reconfigurable devices that will have a transformative impact on quantum information science and engineering.

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We present a low-loss integrated photonics platform in the visible and near ultraviolet regime. Fully-etched waveguides based on atomic layer deposition (ALD) of aluminum oxide operate in a single transverse mode with <3 dB/cm propagation loss at a wavelength of 371 nm. Ring resonators with intrinsic quality factors exceeding 470,000 are demonstrated at 405 nm, and the thermo optic coefficient of ALD aluminum oxide is estimated to be 2.75 × 10 −5 [RIU/ • C]. Absorption loss is sufficiently low to allow on-resonance operation with intracavity powers up to at least 12.5 mW, limited by available laser power. Experimental and simulated data indicates the propagation loss is dominated by sidewall roughness, suggesting lower loss in the blue and UV is achievable. I. INTRODUCTIONThe success of silicon photonics in telecommunications has lead to the application of nano-scale photonics in a variety of fields including computing, nonlinear optics, quantum information processing, and biochemical sensing 1-5 . Compact device footprints and an ability to leverage the same manufacturing techniques employed in the semiconductor industry are strong incentives both for systems designers and in applications where low cost is necessary. Label-free biosensors, optical interconnects for computers and datacenters, integrated lasers with III-V gain media, and phased arrays consisting of thousands of elements have all been demonstrated using the same basic silicon photonic technology 1,5-8 . However, with a bandgap at 1.1 um, silicon is unsuitable for applications which require visible or ultraviolet light, such as optogenetics 9,10 , protein sensing 11,12 , and atom-based sensing, time-keeping, and information processing [13][14][15][16] . A straightforward way of bypassing this limitation is to use silicon nitride, commonly integrated alongside silicon, which has transparency into the visible. Waveguide platforms based on silicon nitride are quite mature, particularly for red and near infrared (NIR) wavelengths. Less progress has been made for devices operating in the blue and near ultraviolet (UV, NUV). This is predominantly due to the high material absorption (>20 dB/cm) that begins in the low 400 nm wavelength range 17 .The most common alternative to silicon nitride for ultraviolet photonics are the III-V nitride materials, particularly aluminum nitride (AlN) and aluminum-gallium nitride alloys (AlGaN) 18 . AlN has a bandgap corresponding to λ ∼ 200 nm and exhibits second-order nonlinearities, making it attractive for integrated nonlinear optics and electrical tuning of reso-2 nant structures. Early demonstrations of ultraviolet waveguides in AlN suffered extremely high loss (389 dB/cm at a wavelength λ = 450 nm) due to a combination of bulk (polycrystalline) material loss and high sidewall roughness 19 . More recent work using nanocrystalline AlN has brought the loss coefficient down by an order of magnitude (∼50 dB/cm at λ = 405 nm) but in a regime where device size is restricted to sub-centimeter or sub-millimeter lengths when s...

We present a Cadence toolkit library written in VerilogA for simulation of electro-optical systems. We have identified and described a set of fundamental photonic components at the physical level such that characteristics of composite devices (e.g. ring modulators) are created organically - by simple instantiation of fundamental primitives. Both the amplitude and phase of optical signals as well as optical-electrical interactions are simulated. We show that the results match other simulations and analytic solutions that have previously been compared to theory for both simple devices, such as ring resonators, and more complicated devices and systems such as single-sideband modulators, WDM links and Pound Drever Hall Locking loops. We also illustrate the capability of such toolkit for co-simulation with electronic circuits, which is a key enabler of the electro-optic system development and verification.

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