Читать книгу VCSEL Industry - Babu Dayal Padullaparthi - Страница 33

In 1982, Iga and co‐workers made a VCSEL with 10 μm length cavity and confirmed the clear VCSEL oscillation [30]. In 1982, Iga’s group made a buried confinement VCSEL with a 6 mA threshold GaAs device using liquid phase epitaxy (LPE) [31]. A major breakthrough was the achievement of continuous‐wave (CW) operation at room temperature (RT) at 820 nm wavelength on GaAs substrate by Iga and Koyama (also from Tokyo Institute of Technology) in 1988 [32, 33]. The device structure is shown in Figure 1.15(a). The device was grown by metal organic chemical vapor deposition (MOCVD). With this achievement, global R&D of VCSELs has outperformed ordinary semiconductor lasers in the area of expertise. The concept of semiconductor DBR demonstration in 1988 [34] and the introduction of multi‐quantum wells into VCSEL [35] contributed to the improvement of VCSEL development in later years.

After this breakthrough from Tokyo Institute of Technology, continuous room‐temperature operation of the VCSEL, as shown in Figure 1.15(b), was also achieved by Jack Jewell and co‐workers at Bell Laboratories in 1989 [36, 37]. The concept of periodic gain or matched gain in quantum wells contributed to reduce the threshold by Larry Coldren and co‐workers [38, 39].

Figure 1.15 Initial VCSELs achieving room‐temperature continuous operation. (a) The VCSEL device that exhibited the first room‐temperature continuous‐wave operation by Koyama and Iga in 1988 [32].

Source: Copyright reserved by Fumio Koyama and Kenichi Iga

(b) A 2D micro‐post array by Jewell and Lee in 1989 [36, 37].

Source: Adapted from IEEE.