A Monolithically Integrated Optical Transmitter

This chapter covers the field of semiconductor photonic integrated circuits (PIC) used in access, metro, long-haul, and undersea telecommunication networks. Although there are many variants to implementing optical integration; the focus is on monolithic integration where multiple semiconductor devices, up to many hundreds in some cases, are integrated onto the same substrate. Monolithic integration poses the greatest technical challenge and the biggest opportunity for bandwidth and size scaling. The PICs discussed here are based on the two most popular semiconductor material systems: Groups III–V indium phosphide-based devices and Group IV silicon-based devices. The chapter also covers the historical evolution of the technology from the decades old original proposal to the current day terabit/s class, coherent PICs.

Integrated Photonics for Data Communications Applications reviews the key concepts, design principles, performance metrics and manufacturing processes from advanced photonic devices to integrated photonic circuits. The book presents an overview of the trends and commercial needs of data communication in data centers and high-performance computing, with contributions from end users presenting key performance indicators. In addition, the fundamental building blocks are reviewed, along with the devices (lasers, modulators, photodetectors and passive devices) that are the individual elements that make up the photonic circuits. These chapters include an overview of device structure and design principles and their impact on performance. Following sections focus on putting these devices together to design and fabricate application-specific photonic integrated circuits to meet performance requirements, along with key areas and challenges critical to the commercial manufacturing of photonic integrated circuits and the supply chains being developed to support innovation and market integration are discussed. This series is led by Dr. Lionel Kimerling Executive at AIM Photonics Academy and Thomas Lord Professor of Materials Science and Engineering at MIT and Dr. Sajan Saini Education Director at AIM Photonics Academy at MIT. Each edited volume features thought-leaders from academia and industry in the four application area fronts (data communications, high-speed wireless, smart sensing, and imaging) and addresses the latest advances. Includes contributions from leading experts and end-users across academia and industry working on the most exciting research directions of integrated photonics for data communications applications Provides an overview of data communication-specific integrated photonics starting from fundamental building block devices to photonic integrated circuits to manufacturing tools and processes Presents key performance metrics, design principles, performance impact of manufacturing variations and operating conditions, as well as pivotal performance benchmarks

Vertical-cavity surface-emitting lasers (VCSELs) emitting at 850 nm wavelength are known for their attractive optical features and a continuously growing range of applications. The main goal of the present thesis is to demonstrate the feasibility of a monolithical integration of VCSELs with PIN-type photodiodes (PDs) for the operation as transceiver (TRx) chips in optical data links. The project milestones comprise the chip and the epitaxial layer design of the VCSEL–PIN PD device based on a traditional AlGaAs/GaAs material system, its fabrication development, electro-optical characterizations, and data transmission in a bidirectional optical link over a single, two-side butt-coupled standard graded-index (GI) multimode fiber (MMF). The monolithic design lowers the costs in the semiconductor technology as well as in packaging and additionally avoids the use of external optics, even though it is employed with a single 50 μm core diameter GI MMF. Thus, the very compact optical link saves space, weight, and module cost. Deep insights into the electro-optical properties of VCSELs and PIN PDs are given by the theoretical description and measurements. The limitations of small-signal modulation responses are of main interest of this thesis. Thus, the dynamic characteristics including the extraction of modeled parasitics are presented. Also the electrical and optical crosstalk between the integrated devices and both transmission channels as well as the fiber alignment tolerances are covered. The results in optical data transmission consisting of various experiments in half-duplex and full-duplex mode, both free-space and fiber-coupled over a single MMF are comprised. The monolithic TRx design is well suited for low-cost, compact optical links over distances of a few hundred meters. Capable to handle data rates of up to 10 Gbit/s and more, these TRx chips can be employed, e.g., to upgrade existing standard MMF networks to bidirectional operation or in mobile, low-cost, automotive networks.

This document reports the results of a one-year program, based on a technical proposal submitted to and accepted by DARPA, to develop a technology for realizing a GaAlAs/GaAs monolithic integrated optoelectronic transmitter for high-speed fiber-optic communications applications. The primary objectives were to: (1) determine a suitable approach for integrating optical and electronic devices in terms of compatible device processing and fabrication, (2) design a simplified high-speed transmitter based on the integration approach which will serve as a building block for future more sophisticated designs, (3) develop the transmitter materials technology, (4) develop the transmitter device components, and (5) fabricate and demonstrate the integrated transmitter. At the end of the programs, all of the objectives were realized except for the demonstration of a functional transmitter. A selective epitaxial growth technique using a dielectric mask was developed for process/fabrication compatibility of the laser with planar ion-implanted GaAs electronic devices with 1 micron-type geometries. Based on this integration approach, a nominal 1-4 Gb/s transmitter set utilizing standard cleaved mirror lasers and field-effect transistor (FET)/Gunn logic drivers was designed, process/fabrication steps defined, and a fabrication mask set generated.

As we approach the end of the present century, the elementary particles of light (photons) are seen to be competing increasingly with the elementary particles of charge (electrons/holes) in the task of transmitting and processing the insatiable amounts of infonnation needed by society. The massive enhancements in electronic signal processing that have taken place since the discovery of the transistor, elegantly demonstrate how we have learned to make use of the strong interactions that exist between assemblages of electrons and holes, disposed in suitably designed geometries, and replicated on an increasingly fine scale. On the other hand, photons interact extremely weakly amongst themselves and all-photonic active circuit elements, where photons control photons, are presently very difficult to realise, particularly in small volumes. Fortunately rapid developments in the design and understanding of semiconductor injection lasers coupled with newly recognized quantum phenomena, that arise when device dimensions become comparable with electronic wavelengths, have clearly demonstrated how efficient and fast the interaction between electrons and photons can be. This latter situation has therefore provided a strong incentive to devise and study monolithic integrated circuits which involve both electrons and photons in their operation. As chapter I notes, it is barely fifteen years ago since the first demonstration of simple optoelectronic integrated circuits were realised using m-V compound semiconductors; these combined either a laser/driver or photodetector/preamplifier combination.