Reliability and manufacturability of 850 nm 50 Gbit/s PAM-4 vertical-cavity surface-emitting lasers

Guangzheng Zhou; Ying Li; Hongyan Yu; Zhaochen Lv; Tian Lan; Luguang Lang; Xuesheng Liu; Zhiyong Wang

doi:10.1117/12.2504064

15 November 2018 Reliability and manufacturability of 850 nm 50 Gbit/s PAM-4 vertical-cavity surface-emitting lasers

Guangzheng Zhou, Ying Li, Hongyan Yu, Zhaochen Lv, Tian Lan, Luguang Lang, Xuesheng Liu, Zhiyong Wang

Proceedings Volume 10964, Tenth International Conference on Information Optics and Photonics; 109640A (2018) https://doi.org/10.1117/12.2504064
Event: Tenth International Conference on Information Optics and Photonics (CIOP 2018), 2018, Beijing, China

Abstract

Reliability and characterization of 850 nm 50 Gbit/s PAM-4 vertical-cavity surface-emitting lasers (VCSELs) are presented. These VCSELs have demonstrated a threshold current of 0.8 mA and a slope efficiency of 0.95 W/A. The maximum optical output power of 9 mW is achieved at a thermal rollover current of 13.5 mA. The optical power is up to 5 mW and the -3dB bandwidth is in excess of 17 GHz at 25°C and 6 mA bias. The current density and power dissipation density are low to 15 kA/cm² and 25.5 kJ/cm² , respectively. The standard deviations of photoluminescence peak wavelength and Fabry-Perot cavity wavelength of epitaxial wafer are 0.75 nm and 2.2 nm, respectively. After 1500 h of the reliability study no degradation or failures of the 22 VCSELs are observed at 80°C in a heating chamber at a bias of 6 mA. Considering high optical absorption of DX center, the impurity doping concentration of 3 pairs of N-DBRs that were adjacent to active region are optimized. The additional SiO₂ passivation layer not only can provide moisture resistance but also provide a photon lifetime tuning. The output power increases by optimizing thickness of SiO₂ layer reducing power dissipation density. Single thin oxide aperture is employed by slowing down the oxidizing rate and improving temperature during a VCSEL oxidation process to thereby reduce stress concentration of an oxidation. Single thin oxide aperture may limit the -3dB bandwidth, but the modulation characteristics can be improved by adopting advanced modulation techniques such as 4-level pulse amplitude modulation (PAM-4).

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Guangzheng Zhou, Ying Li, Hongyan Yu, Zhaochen Lv, Tian Lan, Luguang Lang, Xuesheng Liu, and Zhiyong Wang "Reliability and manufacturability of 850 nm 50 Gbit/s PAM-4 vertical-cavity surface-emitting lasers", Proc. SPIE 10964, Tenth International Conference on Information Optics and Photonics, 109640A (15 November 2018); https://doi.org/10.1117/12.2504064

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