Cheryl Sorace-Agaskar

Photonic ADC: overcoming the bottleneck of electronic jitter

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.

An Interior-Ridge Silicon Microring Modulator

We design and demonstrate a new microring modulator geometry utilizing low-resistance interior ridge contacts and a hard outer waveguide wall to achieve high-speed operation in a device with a large free spectral range (FSR). The depletion-mode silicon microring modulator utilizes a hybrid vertical-horizontal junction to maximize the frequency response for a given voltage within a compact 2.5 μm radius. The 2.5-μm radius microring modulator demonstrates low energy (4.5 fJ/bit) error-free (bit error rate <;10 -12) operation for 30 Gb/s nonreturn-to-zero data transmission without utilizing preemphasis or equalization. The modulator exhibits single mode operation over a wide, uncorrupted FSR of 5.3 THz, the largest reported in a high-speed (>25 Gb/s) modulator. The resulting combination of high-speed, low-energy operation, and a wide FSR offers the potential for very high bandwidth densities in future femtojoule-class communication links.

Electro-optical co-simulation for integrated CMOS photonic circuits with VerilogA

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.

Integrated mode-locked lasers in a CMOS-compatible silicon photonic platform

Integrated components necessary for a mode-locked laser are demonstrated on a platform that allows for monolithic integration with active silicon photonics and CMOS circuitry. CW lasing and Q-switched mode-locking are observed in the full structures.

L-shaped resonant microring (LRM) modulator

A high-speed silicon L-shaped resonant microring modulator, enables directly integrated electrical contacts, 5-μm diameter, 5.3-THz free spectral range, is demonstrated error-free operation up to 30-Gb/s with 1.76-dB insertion loss and 2.8-dB power penalty.

Adiabatic Resonant Microring (ARM) Modulators with Integrated Thermal Tuner

We integrate an efficient thermal tuner (6.2-µW/GHz) within ARM modulators for the first time, yielding 5-THz uncorrupted FSR. The 5.4-um diameter modulator achieves low-power (9-fJ/bit) and high-speed (13-Gb/s) operation with 5.9dB extinction ratio.

Multi-layer integrated photonics from the ultraviolet to the infrared

We demonstrate a scalable multi-layer integrated photonics platform that operates over a multi-octave wavelength range, from the near-ultraviolet (NUV) to the near-infrared (NIR). The platform is CMOS compatible and consists of silicon nitride (Si3N4) and alumina (Al2O3) optical waveguides cladded with silicon dioxide (SiO2). We demonstrate low-loss waveguides and passive components including diffractive vertical grating couplers for input/output (I/O). The multilayer nature of the platform enables complex routing of multiple wavelengths, making it useful for a variety of applications including integrated atomic-molecular-optical (AMO) and biophotonic systems.

Multi-level photonics for trapped-ion quantum computing

A scalable trapped-ion-based quantum-computing architecture requires the capability to optically address individual ions at several wavelengths. We demonstrate a dual-layered silicon nitride photonic platform for integration into planar ion traps designed for trapped-ion control in a 400 to 1100 nm wavelength range.

Electronic-photonic integration for government applications

We provide an overview of electronic-photonic integration techniques and describe our recent work to develop monolithic and hybrid photonic components and integrated circuits (PICS) realized in several material platforms (silicon, silicon nitride, compound semiconductors) for a variety of government applications.

Very Large Scale Silicon Photonics Integration

We present on the demonstration of a number of critical device technologies including record low power modulators, tunable filters, and integrated lasers, along with the worlds largest silicon photonic circuit, integrated on a 300mm platform.