target="_blank" rel="nofollow" href="#uc0a45592-0799-5034-8355-9a21803db937">Chapter 4.
In addition to applications in data centers owned and operated by IT companies, national organizations and universities began to include optical interconnects in computing architectures. For the supercomputer TSUBAME 3.0 by Tokyo Institute of Technology more than 16 000 VCSELs were included in the system. More than 300 000 VCSELs are used in IBM’s top supercomputer. In the world’s fastest (2019 and 2020) supercomputer Fugaku of RIKEN of Japan, it was reported that the numbers of VCSEL chips used was 640 000.
https://www.r‐ccs.riken.jp/en/fugaku/project/outline.
https://www.fujitsu.com/downloads/SUPER/primehpc‐fx1000‐hard‐en.pdf.
1.3.3.2 Computer Mouse
A computer is one way to access the Internet, and a computer mouse is useful for operating a computer. Since around the year 2000, VCSELs have also been applied to computer mice by Hewlett‐Packard; this represented the first high volume use of VCSELs in a consumer market. The use of VCSELs in consumer electronics may be comparable to the development of electronic devices such as LSIs and semiconductor memories. VCSELs used in computer mice will be further discussed in Chapter 8.
1.3.3.3 Laser Printers
VCSEL arrays were introduced into laser printers in 2001 by companies such as Fuji Xerox, Ricoh, and Canon/Sony. Since then, VCSELs have largely replaced edge‐emitting lasers and LEDs in printers. The aforementioned companies have about 80% market share of integrated laser printers in the world. VCSELs in laser printing will be further discussed in Chapter 8.
1.3.4 Stage IV: Spread of VCSEL Photonics
In the fourth stage of VCSEL history, from 2010 to 2020, the true scaling of VCSEL production has been realized. In data communication, highly reliable 850 nm VCSELs are made using InGaAs quantum wells with 3 dB bandwidths exceeding 25 GHz and operated above 70 Gb/s NRZ. New modulation (PAM‐4) standards are made for higher speeds to meet the continued network demand. This is also supported by development of short wavelength WDM VCSELs (in the 850–980 nm band).
In the optical sensing area, high‐power 940 nm VCSELs arrays have been made with optimized designs with power conversion efficiency > 50%, slope efficiency = 1.0 W/A, and with new trends of using multi‐tunnel junctions that offer a power conversion efficiency > 60%, slope efficiency = 3.0 W/A, with power densities of 1 kW/mm2. This facilitated the use of VCSEL arrays in consumer devices (mobile/smart phones/smart homes), infrastructure and transport applications incorporating LiDAR, surveillance and night vision products, robots, drones, IoT, and so on. Further applications include multi‐mode VCSEL arrays in LiDARs at 905 nm, 850 nm, and 1060 nm; large‐scale 940 nm arrays in industrial heating systems. On the other hand, single‐mode VCSELs are being applied to optical coherence tomography (1060 nm) and atomic clocks. Details and references can be found in related chapters.
The multi‐function ability of VCSELs further expanded manufacturing bases across the world with investments prompting high market demands never seen before. This also triggered high‐volume manufacturing from 4" (100 mm) to 6" (150 mm) for optical sensor products. All these items will be discussed in Chapters 3–9.
1.3.5 Stage V: VCSEL Industry
In the fifth stage (2020 onward) VCSELs will continue to expand in global volume production and find new application areas. The ever‐increasing demand for data communication and emerging technologies in machine vision, artificial intelligence (AI), augmented reality (AR), mixed reality (MR), and the Internet of Things (IoT) will drive global demand for VCSELs [52]. In this stage, VCSELs will affect nearly all aspects of human life. Details on computer vision (AR, MR, VR) will be introduced in Chapter 5. The application to automotive LiDARs and autonomous shuttles will be covered in Chapter 6.
1.4 Timeline and Milestones
1.4.1 Milestones of VCSEL Research and Development
In Table 1.2 we show a list of key benchmark events based on 44 years of basic research and commercial product developments on semiconductor lasers and VCSELs.
1.4.2 Single‐Mode and Multi‐Mode Behavior
Semiconductor lasers oscillate in different modes (power radiation patterns) that depend on the dimensions of the optical resonator. Especially for VCSELs, the mode structure or pattern depends on the size and shape of the oxide aperture (mode) diameter used for current and optical confinement [53, 54]. Several kinds of modes appear in the emission spectra, namely longitudinal, transverse, single, and multi‐modes. In Figure 1.16 we show how the behavior of VCSEL in single longitudinal and multi‐transverse (and longitudinal) operation. More details on the VCSEL mode structure will be discussed in Chapter 2.
Table 1.2 Milestones of surface emitting laser research and development.
| 1977 | Surface‐emitting laser concept proposed |
| 1979 | First device demonstrated (77 K, pulsed) |
| 1988 | First RT CW operation |
| 1988 | Semiconductor DBR |
| 1989 | QW VCSEL |
| 1989 | Micro‐post QW laser RT CW (Bell Labs) |
| 1989 | Periodic gain proposed (UCSB) |
| 1990 | AlGaAs hydro‐oxidization (UIUC) |
| 1992 | VCSEL mechanical tuning demonstrated |
| 1995‐ | Low threshold device competition Ith < 0.1 mA |
| 1995 | MEMS tunable VCSEL (USB) |
| 1996 | VCSEL commercialization (Honeywell) |
| 1999 | VCSEL LAN |
| 2000 | Oxide aperture device reliability |
| 2001 | VCSEL printer (Fuji, Xerox), |
| 2001 | Computer mouse (HP) |