Anna Tauke-Pedretti

Integrated Photonics for Low-Power Packet Networking

Communications interconnects and networks will continue to play a large role in contributing to the global carbon footprint, especially in data center and cloud-computing applications exponential growth in capacity. Key to maximizing the benefits of photonics technology is highly functional, lower power, and large-scale photonics integration. In this paper, we report on the latest advances in the photonic integration technologies used for asynchronous optical packet switching using an example photonic integrated switched optical router, the label switched optical router architecture. We report measurements of the power consumed by the photonic circuits in performing their intended function, the electronics required to bias the photonics, processing electronics, and required cooling technology. Data is presented to show that there is room (potentially greater than 10 ×) for improvement in the router packet-forwarding plane. The purpose of this exercise is not to provide a comparison of all-optical versus electronic routers, rather to present a data point on actual measurements of the power contributions for various photonic integration technologies of an all-optical packet router that has been demonstrated and conclude, where the technology can move to reduce power consumption for high-capacity packet routing systems.

High saturation power and high gain integrated photoreceivers

A novel monolithically integrated semiconductor optical amplifier (SOA) receiver is presented. This receiver implements a flared SOA and tapered quantum-well detector. SOAs exhibited 22-dB unsaturated gain and 15.7-dBm output power at the 1-dB gain compression point while the receiver demonstrated 15-GHz bandwidth and -10.5-dBm sensitivity.

Advanced integration schemes for high-functionality/high-performance photonic integrated circuits

The evolution of optical communication systems has facilitated the required bandwidth to meet the increasing data rate demands. However, as the peripheral technologies have progressed to meet the requirements of advanced systems, an abundance of viable solutions and products have emerged. The finite market for these products will inevitably force a paradigm shift upon the communications industry. Monolithic integration is a key technology that will facilitate this shift as it will provide solutions at low cost with reduced power dissipation and foot-print in the form of highly functional optical components based on photonic integrated circuits (PICs). In this manuscript, we discuss the advantages, potential applications, and challenges of photonic integration. After a brief overview of various integration techniques, we present our novel approaches to increase the performance of the individual components comprising highly functional PICs.

Mutual Injection Locking of Monolithically Integrated Coupled-Cavity DBR Lasers

We present a photonic integrated circuit (PIC) composed of two strongly coupled distributed Bragg reflector (DBR) lasers. This PIC utilizes the dynamics of mutual injection locking to increase the relaxation resonance frequency from 3 GHz to beyond 30 GHz. Mutual injection-locking and external injection-locking operation are compared.

Separate Absorption and Modulation Mach-Zehnder Wavelength Converter

A monolithic separate absorption and moduation region (SAM) wavelength converter is demonstrated. The transmitter consists of a sampled-grating DBR (SGDBR) laser and a series-push-pull Mach-Zehnder modulator. The preamplified receiver is composed of a flared semiconductor optical amplifier and a quantum-well pin photodetector. Integrated resistors and capacitors are used to minimize microwave losses and remove the need for external bias tees. The design, fabrication, and operation of this photonic integrated circuit is presented. Small-signal response measurements show a device bandwidth in excess of 20 GHz. Operation at 40 Gbps with NRZ data shows less than a 2.5-dB power penalty across the 32-nm laser tuning range with no additional power penalty for conversion to the input wavelength.

40 Gb/s Field-Modulated Wavelength Converters for All-Optical Packet Switching

We present a high-functionality photonic integrated circuit that performs field-modulated wavelength conversion. This device incorporates an on-chip sampled grating distributed Bragg reflector laser for wide tunability. Wavelength conversion is accomplished using a preamplified semiconductor optical amplifier photodiode receiver interconnected with a traveling-wave modulator to form a high-speed optical gate. This paper discusses the design and performance of this device, as well as its potential for optical packet switching applications. Error-free wavelength conversion is demonstrated at 40 Gb/s with 1-3 dB power penalty compared with back-to-back transmission over 22 nm of input and output tuning. Output extinction in all cases is greater than 9 dB, and conversion efficiency ranges from -2 to -6 dB over the tuning range. This device additionally demonstrates the capability for external 10 Gb/s modulation, which can be used for optical label encoding.

Widely Tunable Separate Absorption and Modulation Wavelength Converter With Integrated Microwave Termination

A widely tunable wavelength converter utilizing a separate absorption and modulation configuration and only dc bias connections is demonstrated. The device integrates an SG-DBR laser with a traveling-wave electroabsorption modulator and an optically pre-amplified receiver and introduces a simplified bias scheme by the inclusion of passive resistor and capacitor circuit elements. We discuss a the design of these passive elements and their compatibility with fabrication of photonic integrated circuits. The device demonstrates over 12 GHz optical bandwidth and error free 10 Gb/s wavelength conversion is achieved with less than 2.5 dB power penalty over 25 nm of output tuning.

Monolithically-integrated 40 Gbit/s widely-tunable transmitter using series push-pull Mach-Zehnder modulator SOA and sampled-grating DBR laser

A monolithically integrated widely-tunable transmitter using a series push-pull Mach-Zehnder electrode structure with a semiconductor optical amplifier and SGDBR laser is presented suitable for 40 Gbit/s systems with tuning over 34 nm.

Voltage Matching and Optimal Cell Compositions for Microsystem-Enabled Photovoltaic Modules

In this paper, we calculate optimal cell compositions and voltage-matching considerations for independently connected junctions, such as those proposed for microsystem-enabled photovoltaic modules. The calculations show that designs using voltage-matched independent junctions can achieve better yearly efficiency across temperature and spectrum than traditional monolithic cells. Voltage matching is shown to be relatively insensitive to temperature and spectrum but is dependent on open-circuit voltage as a measure of cell efficiency. If the efficiencies and, hence, maximum power point voltages are known a priori, voltage matching can usually yield yearly efficiencies of 98-99% of the efficiency of a system with each cell operating at its own maximum power point.

Optically Pumped Midinfrared Laser With Simultaneous Dual-Wavelength Emission

We demonstrate optically pumped semiconductor lasers that are capable of simultaneously emitting at two different midinfrared wavelengths. The wavelengths can be independently chosen and designed into the heterostructure. The epitaxial III-V antimonide structure employs two sets of type-II quantum wells in a waveguide that is partitioned by a thin electrical barrier that is transparent to the pump radiation. Two-color devices emitting at wavelengths as far apart as ~4.0 and ~5.4 mum are reported.