can be said that most of us are using VCSELs even without recognizing them. This small device is becoming a powerful tool that supports the flow of information in everyday life.
The current technological progress has caused many paradigm‐shifts in the information communication world, and we look at the new world of optoelectronics centering on VCSELs because they will be firmly rooted as the devices that enable the IoT and AI smarter. As for the descriptions of the theory and mechanism of the laser, we discuss the VCSEL from the industrial point of view in this book.
Applications of surface‐emitting lasers are expanding, and the numbers of researchers, developers, and manufacturers who handle them are also increasing. The book is intended for a broader audience in industry and introduces the basic ideas and the scope of applications that have not necessarily been written in most of academic papers and textbooks.
We would be extremely pleased if this book could serve as an opening gate for emerging new VCSEL industries.
Kenichi Iga
Tokyo, Japan
July 11, 2021
Introduction
VCSEL, or vertical‐cavity surface‐emitting laser is now a buzzword in the science and engineering community. The excitement is driven by the promise of 3D applications everywhere, including smart phones, cars, gaming, and other forms of augmented or virtual reality. The new era for VCSELs was ushered in with the introduction of face recognition technology in the iPhone X. Since commercial introduction in 1996, VCSELs have long been the workhorse of data communication and data centers. As global Internet connectivity has grown, so has the VCSEL industry, expanded from producing a few tens of 75 mm wafers per year to thousands of 150 mm wafers today. Speeds have grown from 1 Gbps to over 56 Gbps in commercial data center products. VCSELs also found success in optical mice, autofocus assist, atomic clocks, and many other applications. But all of these taken together still did not drive interest of large‐scale industrial production that consumer electronics could demand. In fact, despite the success of VCSELs, it was still considered a cottage industry until just a few years ago. One of the key advantages of VCSELs—small size—was limiting the wafer volume production to small boutique fabs. Early applications did not take advantage of another key attribute of VCSELs, scalability into 2D arrays of emitters. The typical VCSEL die used in a 3D sensing application is more than 20x the size of one used in data communications! This scaling of chip size and market opportunity has caused a huge surge in VCSEL wafer demand. Today high‐volume applications in the consumer, automotive, and industrial sectors have driven VCSELs to become a multi‐billion‐dollar market, and that excludes traditional datacom and data center interconnects. With all of the activity around VCSELs, several engineering textbooks and references of VCSEL technology have been written, but none has focused on the basic operating principles, and none included aspects of manufacturing challenges and market dynamics.
This book is targeted to young entrepreneurs, managers, engineers, and researchers in a wide range of industries to understand how VCSELs are used in high‐volume communication and sensing applications, to identify key manufacturing challenges, and future market prospects. In contrast to traditional academic textbooks, the technical content is focused on engineering design and the application of VCSELs with few mathematical expressions. The authors use a unique style of illustrations and practical engineering tenets to describe VCSEL operating principles and how they are used in a variety of applications. The book is a collection of experiences and the authors’ views on topics that have and will drive the continued expansion of the VCSEL market. In other words, the book gives clear insight to understanding the overall landscape of the VCSEL industry and helps readers access the risks and rewards of the many segments. Readers are introduced to the basic operating principles of VCSELs that are relevant to application design, and a specific background in semiconductor lasers is not necessarily required. The book is focused on engineering understanding and industrial production of VCSELs and their applications. We are proud to include the historical perspectives and future insight in this book from Professor Kenichi Iga, the inventor of the VCSEL, and the 50th anniversary of the birth of VCSEL on March 22, 2027!
Chapter 1 introduces the history of semiconductor lasers, in particular VCSELs, and the potential of VCSELs as major components of choice in photonic applications. Chapter 2 describes the basic structure of a VCSEL and its fundamental operating characteristics. Chapter 3 describes the landscape of the VCSEL industry including leading participants, market size, chip demand, manufacturing challenges, and a few commercial products as examples. Chapter 4 deals with the high‐speed multi‐mode VCSELs for datacom applications and its potential for 100G and 400G networks. Chapter 5 focuses on multi‐mode VCSEL arrays for short‐range 3D sensing (up to 10 m) applications including proximity sensing in automobiles, autofocus functions for augmented reality, and facial recognition. Chapter 6 considers multi‐mode VCSEL array chips as light sources for flash‐ and scan‐based LiDARs for long‐distance ranging (up to 250 m) in the automotive industry. Chapter 7 describes multi‐mode VCSEL‐based illuminators in night vision and security systems and continues the scaling of VCSELs to kW levels used in industrial heating modules. Chapter 8 focuses on single‐mode VCSELs for sensing applications, and Chapter 9 deals with single‐mode communications applications that will be the starting point for single‐ and entangled‐photon sources for many quantum applications. Chapter 10 summarizes the present trends and provides insight into the future directions for VCSELs and their impact on commercial products. The authors also provide several topics that are closely connected to the aforementioned chapters and cover some of the other considerations of VCSEL industrial production as appendices. These include design, epi‐structure growth, wafer fab, testing, reliability, eye‐safety, short (GaN and display), and visible‐wavelength VCSEL applications, as well as photodetectors.
Babu Dayal Padullaparthi Hong Kong, July 31, 2021
Jim Tatum Celina, Texas/USA, July 30, 2021
Acknowledgments
The authors express their sincere gratitude to all who made this book possible in one of the most turbulent times in decades. Firstly, thanks to Dr. Nim K Cheung, IEEE Series Editor for inviting us to write a book on VCSELs in November 2019. Secondly, to the IEEE Press and Wiley Publishing staff, especially to Ms. Mary Hatcher and Ms. Teresa Netzler for their support in accepting our regular book proposal on July 2020 from multiple authors for a VCSEL industry reference that initially started as a short e‐book! We thank all the reviewers of the proposal and manuscript production stages; without their timely support, the authors could not have completed this book in such a short period of time. The authors also sincerely thank all of the image contributors (companies and professional societies listed in page xxv, 311–312) in this book for their copyright permissions.
The authors would also like to thank the many co‐workers, students, and colleagues that we have worked with over the years. We have learned a lot about VCSELs and especially have learned that these are one of the most complicated two‐terminal devices ever manufactured. Writing this book has reinforced the breadth and depth of understanding needed in multi‐disciplinary physics to design and manufacture VCSELs. They encompass aspects of mechanical, electrical, thermal, optical and solid‐state physics are truly remarkable devices. Along with the technical challenges, the realization of market forces, the drive of standardization, and the necessity of meeting commercial objectives have been an amazing journey for all of us. The advances in so many interdisciplinary aspects of engineering have enabled more than 1 billion devices manufactured since its invention in 1977.
Babu Dayal