The surface emitting laser is brightening. Industrially, we are in a period of rapid growth: it is a light source that supports applications ranging from the physical layer of AI (artificial intelligence) to the IoT (internet of things). This book is a story about the invention of the surface emitting laser and its research and production up to now.
A laser is a device that emits a laser beam that is irradiated by projection mapping, but the laser we will talk about here is one made of a semiconductor smaller than a poppy seed. I invented the “surface emitting laser” in 1977; it is a surface-type laser made of a semiconductor, and its size is several mm, which is about two digits smaller than that of a normal semiconductor laser [1977 IGA]. It is so named because laser light is emitted from the surface of the semiconductor. In this new laser, since the light resonating direction is vertical, it is called a vertical cavity surface emitting laser (VCSEL, pronounced “viksel”). The term “odyssey” is used in the title to suggest a long journey or epic poem.
I continued basic research for a long time after inventing the VCSEL in 1977, but global mass production began around 1999, when the internet became popular rapidly. For example, the IIJ (Internet Initiative Japan) was started in 1995. The internet is a new communication method implemented by optical communication networks and computers. Surface emitting lasers have been adopted as light sources that make up the LANs (local area networks) of the internet.
On the other hand, information-related companies such as Google, Yahoo, Amazon, Gurunavi, and Rakuten have grown due to the internet. There is a huge information storage called “the cloud” (a mechanism for storing information in memory, such as hard disks, to read and use it). A huge optical fiber network sends information to data centers like the arteries and veins of blood vessels. One of the light sources used is a surface emitting laser. In addition, many computer users have a mouse, which uses a surface emitting laser as a sensor to track its position with coherent light. The number of units produced so far is more than 1.1 billion. In 2017, it was also adopted for iPhoneX face recognition.
Everybody is using it without recognizing it, but a small surface emitting laser is a powerful tool that supports the flow of information.
Why this book?
I studied at a national university called the Tokyo Institute of Technology, pursued education and research, and after retirement obtained the position of Executive Director to support research at the Japan Society for the Promotion of Science. After that, I served as the president of the Tokyo Institute of Technology. Free to apply myself to any interests, I can now see science and technology from a broader perspective. In addition, in return for studying and researching at the government expense, I want to leave some kind of archive for future young people, and so I have been writing and giving lectures.
In the current technological situation that has caused many paradigm shifts in the information communication world, I would like to look at the new world of optoelectronics centering on surface emitting lasers because it will be firmly rooted as hardware that embodies the IoT and AI. Instead of describing the theory and mechanism of the laser, let us make it a long journey of wandering—an epic, as the English title suggests.
The title has a background. As introduced by co-author Genichi Hatakoshi in “Treasure Micro-Box of Optoelectronics I” [2019 IGA], The Laser Odyssey was the autobiography of Theodore Maiman, who realized the laser for the first time, and A Jazz Odyssey was written by Oscar Peterson, a master of jazz piano—both books impressed us, and I would be extremely happy if I could borrow a book title from them. So I finally made up my mind to name my book The VCSEL Odyssey.
Whom is this book for?
Applications of surface emitting lasers are expanding; and the numbers of researchers, developers, and businesspeople who handle them are also increasing. The book is intended for a broad audience, because the research history of the surface emitting laser, the basic idea, and the scope of application were not necessarily written in academic papers. Of course, for all teachers who teach at universities and other educational institutions, and students, etc., this book may be a kind of break or supplement during research and study for teachers and students.
Also, it would be fortunate if it could be a milestone to reflect on the history of optoelectronics that has developed since the advent of surface emitting lasers.
November 30, 2018 (Original edition)
June 15, 2020 (1st English edition)