ranging or object detection (~250 m or longer) can also be done using the sensing concept shown in Figure 1.16 for automobile by using LiDARs. This is sometimes known as vehicle‐to‐everything (V2X). LiDARs use individually or row/column addressable arrays of VCSELs or edge‐emitting laser arrays to illuminate the scene either through a single flash, sequential flashes by selectively addressing the emitters, or scan functions, and the object image is created through powerful signal processing and artificial intelligence (AI).
Besides ToF, more precise object measurement techniques such as optical phased arrays (OPA) or frequency modulations (FMCW) are also used for advanced driver‐assistance systems (ADAS). Details of other applications are discussed in Chapters 6–9.
To facilitate comprehension, supplementary information is given as appendices on generic VCSEL design (Appendix A), epitaxial growth (Appendix B), wafer processing (Appendix C), testing (Appendix D), reliability and qualification (Appendix E), and eye‐safety issues (Appendix F). Special notes on display (Appendix G), red VCSELs (Appendix H), photodetectors (Appendix J), and GaN VCSELs (Appendix I) and are also provided.
Figure 1.18 Published papers on VCSEL.
Source: Data taken from Google Scholar on November 2, 2020. (Searching key words: “VCSEL” OR “vertical‐cavity surface‐emitting laser” OR “surface emitting laser” in the text or title.) [Image courtesy of Tomoyuki Miyamoto, Tokyo Institute of Technology.]
1.5 State of VCSEL Development
1.5.1 Published Papers
Figure 1.18 shows the number of published papers per year and accumulated statistics. Note that the total number of related papers has reached about 50,000 as of 2020. The yearly publications have skyrocketed over the last decade, indicating that commercialization is taking place.
1.5.2 Toward VCSEL Photonics
Ever since Honeywell started VCSEL commercialization and introduced the first reliable product in around 1996 [57], VCSEL technology has made a huge impact on several key industries with multiple growth windows. Thanks to several commercial epi‐houses, III‐V opto‐foundries, and other equipment vendors, researchers and engineers have overcome great challenges to make VCSEL‐based commercial products a practical reality since the beginning of 2021.
After 44 years of VCSEL invention [25] and the marathon industry efforts to realize volume manufacturing, it is not surprising that most people carry a VCSEL device along with them, if not a few! This means VCSELs have rapidly grown up, fully matured, and penetrated into commercial products that affect the daily lives of humans.
Four major industries dominate most of the VCSEL applications space (called core products), while few other neighboring fields are also emerging in the entire VCSEL application seabed. On core applications, the first is high‐speed VCSELs for data communications and data center applications. There is a steady demand for 100 to 300 m active optical cables in 100–400 Gb/s data center needs, HDMI AOC, USB‐3 (c‐type), and so on. The world’s fastest (as of 2019 and 2020) high‐performance computer, Fugaku, uses more than 6 400 000 chips of VCSELs for AOCs.
The second and biggest opportunity is high‐power VCSEL arrays for consumer electronics (3D sensing and imaging up to 10 m), including illumination, face recognition (FR), and augmented reality (AR) needs. This extends to object detection for autonomous vehicles and intelligent transport through powerful long‐range LiDARs up to 250 m or beyond. Further high‐power VCSEL arrays (where 100 000 to a few million units of emitters are needed) find applications in industrial heating.
Furthermore, we find VCSEL applications in neighboring areas such as coherent communication, laser printers, additive manufacturing, gas sensing and spectroscopy, biometrics such as optical coherence tomography (OCT) and iris scans, gaming (VR and MR), robotics, and drones attracting considerable investments, particularly on AI programming, smart home and IoT, and automotive Ethernet and even to quantum computing.
1.5.3 Toward VCSEL High‐Volume Manufacturing
The proliferation of VCSELs into several industries and their use in countless commercial products make the VCSEL industry bright and vibrant. In Figure 1.19 we show the market of VCSELs estimated in 2021. It is quite amazing to realize that hundreds of millions of VCSELs have been deployed. The overall market is forecast to continue to grow in current core applications, and it is expected that even more areas will be uncovered to edge areas in the future. The large shipping volume has created an ecosystem of vertically integrated manufacturers as well as robust foundry vendors. With millions of epi‐wafers processed, multibillion‐dollar market forecasts, and nearly a trillion of VSCEL units shipped, undoubtedly VCSELs are the future optical components of choice and are cementing their presence in the photonics industry!
Figure 1.19 Application fields of VCSEL market as of 2021; data taken from various sources.
Source: Figure by B. D. Padullaparthi and K. Iga [copyright reserved by authors].
In Figure 1.20, we show a modified hype cycle of VCSEL industrialization. This shows the timeline of VCSEL industrialization based on Iga’s personal limited knowledge. In Chapter 10, we will discuss this matter after reviewing all the items in technical chapters by all the authors and editor by including other applications.
Figure 1.20 The modified hype cycle of VCSEL industrialization.
Source: K. Iga’s observation in the middle of 2020 [copyright reserved by author].
