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

Paper Details

Date Published: 15 November 2018
PDF: 7 pages
Proc. SPIE 10964, Tenth International Conference on Information Optics and Photonics, 109640A (15 November 2018); doi: 10.1117/12.2504064
Show Author Affiliations
Guangzheng Zhou, Beijing Univ. of Technology (China)
Ying Li, Beijing Univ. of Technology (China)
Hongyan Yu, Beijing Univ. of Technology (China)
Zhaochen Lv, Beijing Univ. of Technology (China)
Tian Lan, Beijing Univ. of Technology (China)
Luguang Lang, Beijing Univ. of Technology (China)
Xuesheng Liu, Beijing Univ. of Technology (China)
Zhiyong Wang, Beijing Univ. of Technology (China)


Published in SPIE Proceedings Vol. 10964:
Tenth International Conference on Information Optics and Photonics
Yue Yang, Editor(s)

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