Coplanar electrode directly modulated lasers with different cavity length. Issue 5 (21st January 2021)

• Record Type: Journal Article
• Authors: Xu, Borui; Sun, Jiazheng; Xia, Shijun; Zhu, Sha; Liu, Yu; Zhu, Ninghua; Sun, Wenhui
• Is Part Of: Microwave and optical technology letters. Volume 63:Issue 5(2021)
• Page Start: 1434
• Page End: 1439
• Publication Date: 2021-01-21
• Subjects: bandwidth -- cavity length -- coplanar electrode -- directly modulated laser (DML) -- relaxation oscillation frequency; Microwaves -- Periodicals; Optics -- Periodicals; 621
• DOI: 10.1002/mop.32780
• Languages: English
• ISSNs: 0895-2477

Abstract

Abstract: A ridge‐waveguide (RW) directly modulated laser (DML) with a coplanar electrode structure is proposed and measured in this paper. Since utilizing the coplanar electrode can significantly reduce parasitic capacitance, the frequency responses of DMLs exhibit a quite low roll‐off. Shortening the cavity length L is attractive to enhance the high‐speed performance of DMLs, but it will increase the mirror loss and the chip resistance at the same time. We analyzed the static and dynamic characteristics of 200‐μm, 250‐μm, and 300‐μm lasers experimentally and theoretically to investigate the impact of L on the coplanar‐electrode DML. Shortening the cavity length can improve the relaxation oscillation frequency f r effectively. The 200‐μm DML achieves a bandwidth of 15.3 GHz. The f r is the most important limiting factor for the laser to obtain a wide bandwidth. Decreasing L and increasing the differential gain are promising for the further improvement of f r . However, shortening L causes a more severe thermal effect and the deterioration of the linearity. This trade‐off must be considered in the future study.