System-On-Chip Photonic Integrated Circuits (Invited)
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System-On-Chip Photonic Integrated Circuits (Invited) Fred Kish, Fellow IEEE, Vikrant Lal, Peter Evans, Scott Corzine, Mehrdad Ziari, Tim Butrie, Mike Reffle, Huan-Shang Tsai, Andrew Dentai, Fellow IEEE, Jacco Pleumeekers, Mark Missey, Matt Fisher, Sanjeev Murthy, Randal Salvatore, Parmijit Samra, Scott Demars, Naksup Kim, Adam James, Amir Hosseini, Pavel Studenkov, Matthias Lauermann, Ryan Going, Mingzhi Lu, Jiaming Zhang, Jie Tang, Jeff Bostak, Thomas Vallaitis, Matthias Kuntz, Don Pavinski, Andrew Karanicolas, Babak Behnia, Darrell Engel, Omer Khayam, Nikhil Modi, Mohammad R. Chitgarha, Pierre Mertz, Wilson Ko, Robert Maher, John Osenbach, Jeff Rahn, Han Sun, Kuang-Tsan Wu, Matthew Mitchell, David Welch, Fellow IEEE electronic IC concept to photonics. This photonic integrated Abstract—Key advances which enabled the InP photonic circuit, or PIC, was first proposed by Miller [6] in 1969. Over integrated circuit (PIC) and the subsequent progression of InP the past 47 plus years since this publication, there have been PICs to fully integrated multi-channel DWDM system-on-chip numerous research demonstrations of PICs; however, the (SOC) PICs are described. Furthermore, the current state-of-the- ability for the economic value derived from an integrated art commercial multi-channel SOC PICs are reviewed as well as key trends and technologies for the future of InP-based PICs in component to outweigh the cost of the integration itself has optical communications. limited their commercial success as well as the investment in their development. To date, the application that has primarily Index Terms— Photonic Integrated Circuit, optical receivers, driven the introduction and scaling of PICs has been their use optical transmitters. for optical communications. This paper will review the many seminal contributions, inventions and discoveries that were critical to the development I. INTRODUCTION of PICs in the field of optical communications. The progression he modern electronics era began with the invention of the from the first PICs to today’s fully integrated system-on-chip Ttransistor and the discovery of minority carrier injection (SOC) state-of-the-art devices used in optical communications [1]. The amazing advances of modern electronics are applications will also be examined. Furthermore, promising underpinned by the scalable nature of semiconductor technologies for future generations of PICs will be discussed to technology and the invention of the integrated circuit (IC) further enable PIC scaling and more ubiquitous use of PICs in [2, 3]. The IC has had unparalleled impact on our modern world optical communications. as a result of the ability of semiconductor and transistor II. PRE-HISTORY OF PHOTONIC INTEGRATED CIRCUITS technology to continually increase the functionality, performance, and reliability of solid-state circuits, while A. Foundational Work reducing their size, power, and costs. This IC scaling has been The invention of the transistor [1] and electronic IC [2,3] laid exponential, resulting in chips today that contain over a billion the foundation for the photonic IC. In this section, we recognize transistors at a cost per transistor of <0.1 microcents. An the essential role of many contributions in science and essential value of the IC is the ability to realize many of the technology that built upon this foundation to realize the first aforementioned improvements by eliminating the need to photonic IC and the progression of PICs used in optical discretely package and assemble individual devices or smaller communications. circuits by providing the device and circuit connections via Table I shows a list of some key foundational advances that semiconductor batch and wafer scale processing. enabled photonic ICs. One of the most significant such The development of the semiconductor laser [4], the advances was the invention of the laser in 1960 [7]. As semiconductor alloy laser [5], and the associated viability of referenced previously, the transistor enabled the discovery of compound semiconductor alloys [5] (which enabled device minority carrier injection. This phenomenon, applied to direct structures with “tunable” bandgaps), led the groundwork for gap semiconductors [8], led to the study of band-to-band light modern optoelectronics and the possibility of extending the generation from carrier recombination, and ultimately, in Manuscript received September 22, 2016. Authors are with Infinera Corporation, Sunnyvale, CA 94089 USA (corresponding author: Fred A. Kish: 408-572-5200; e-mail: [email protected]). Digital Object Identifier 10.1109/JSTQE.2017.2717863 1077-260X © 2017 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission. See http://www.ieee.org/publications standards/publications/rights/index.html for more information. JSTQE-INV-IPIP2018-06851-2017 2 conjunction with the invention of the laser, led to the realization Several points were essential in the statement of the proposal of the semiconductor laser [4]. Almost coincidentally, the first for the photonic IC by Stewart. First, was the statement “…if III-V alloy laser was demonstrated by Holonyak and Bevaqua realized”. This is important to underscore as by 1969, while the [5]. This work was foundational in that it demonstrated alloy most of the key science concepts were established, many of the disorder and defects were not intrinsic to III-V alloys. Thus, underlying technologies to realize a photonic IC had not been III-V alloy materials were viable to make semiconductor developed. Secondly, was the phrase “….economy should devices (including optoelectronic devices) wherein the bandgap ultimately result”. Even after their realization, PICs have been could be “tuned’ by varying the alloy composition. A further generally economically challenged to provide the same value seminal invention in the development of semiconductor lasers proposition as electronic integrated circuits for a number of was the proposal to utilize heterojunctions to simultaneously reasons as described by Kaminow [14], including: provide optical and carrier confinement [9]. This advance enabled the development of the first room-temperature (RT) 1) Active photonic devices require a much more diverse set continuous wave (cw) operation of a semiconductor laser [10] of semiconductor materials (binary, ternary, quaternary) by virtue of employing a double heterostructure (DH) device that are harder to control and manufacture than electronic design. The III-V alloy and hetorojunction are the basis for ICs; virtually all III-V optoelectronic commercial devices deployed 2) The fundamental size limit for photonic device sizes is today. significantly larger than that of electrical devices (photon versus electron wavelength) and hence are not subject to TABLE I the same level of dimensional scaling; SOME KEY FOUNDATIONAL ADVANCES ENABLING PHOTONIC ICS (PICS) 3) PICs require a more diverse set of building blocks than electronic ICs (lasers, detectors, modulators, Year Technology Break-Through Reference multiplexers, demultiplexers, attenuators, amplifiers, 1883 Light detection in a semiconductor [12] polarization management devices, phase adjusters, etc.); 1947 Transistor (including the discovery of minority [1] 4) Applications and circuit designs are not as scalable (using carrier injection) repeated blocks); 1959 Electronic integrated circuit (IC) [2], [3] 5) Progressively complex and sizeable applications have not 1960 Invention of the LASER [7] 1961 Light modulation in a III-V semiconductors [11] emerged to fund continuous investment in the technology 1962 Semiconductor injection laser [4] and manufacturing. 1962 III-V alloy injection laser [5] 1963 Heterojunction semiconductor laser proposal [9] In order to overcome these challenges, a new set of fabrication 1966 Low-loss fiber-optic transmission [13] processes and set of optical device building blocks needed to be 1969 Double heterojunction injection laser (RT, cw) [10] 1969 Photonic IC proposal [6] developed to realize practical photonic ICs. Table II shows some of the key process technologies that were required to be RT = room temperature; cw = continuous wave. developed to realize viable photonic ICs for optical communications. Around this time, it was also shown that a III-V semiconductor could modulate [11] light with an external TABLE II applied voltage. This phenomenon, combined with the ESSENTIAL NEW FABRICATION PROCESSES FOR PHOTONIC ICS previously known light-detectivity of semiconductors [12] laid Year Technology Break-Through Reference the science foundation for the key functionality required to 1956 Bulk Czochralski crystal growth of III-V materials [15] build a photonic IC. The invention of low-loss glass fibers in 1961 Vapor phase epitaxy (VPE) of III-V alloys [18] the optical frequency spectrum by Kao and Hockham [13] 1962 Bulk crystal growth of InP [16] 1962 Cleaved optical facets [27] established the application space for what has been the “killer 1970 Viability of III-V quaternary alloys [29] application” for photonic ICs: optical communications. The (III-V quaternary alloy injection laser) culmination of these seminal advances was the proposal of the 1974 DFB injection laser demonstration [28] (integrated mirrors) photonic IC by Miller [6] in The Bell System Technical Journal: 1976 InGaAsP / InP laser demonstration (RT, cw) [30] 1977 Viability of Metal Organic Vapor Phase Epitaxy [19] “This paper outlines a proposal for a miniature form of (MOVPE) laser beam circuitry…Photolithographic