A Cascaded Tunable DFB Semiconductor Laser With Compact Structure

• Published in: IEEE journal of quantum electronics Vol. 54; no. 4; pp. 1 - 11
• Main Authors: Zhao, Yong, Shi, Yuechun, Li, Jia, Liu, Shengping, Xiao, Rulei, Li, Lianyan, Lu, Jun, Chen, Xiangfei
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.08.2018; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Bragg grating; Distributed feedback devices; Gratings; Laser modes; Laser theory; Laser tuning; Lasers; optical communication; phase shift; Quantum cascade lasers; tunable laser; Tunable lasers; Wave division multiplexing; Wavelength division multiplexing
• ISSN: 0018-9197; 1558-1713
• DOI: 10.1109/JQE.2018.2837752

A compact cascaded tunable distributed feedback semiconductor laser is proposed and theoretically analyzed. Each laser section (LS) is formed by two adjacent grating sections (GSs) with slightly different Bragg wavelengths and a π phase shift in the joint between them. A step-wise grating period profile is designed to realize multi-channel lasing. Since two LSs share a common GS, the total cavity length of the tunable laser is significantly reduced. As an example, a tunable laser with six GSs and five π phase shifts was designed and analyzed, resulting in a continuous tuning range of 12 nm. The total length of the laser is reduced by 40% compared with the conventional structure. Furthermore, an improved structure with apodized grating in each GS is also proposed. The single mode stability and fabrication tolerance are significantly improved. Due to the compact structure, the cost of the proposed laser can be highly reduced. Therefore, we think the proposed structure would benefit the practical applications to the low cost tunable lasers in wavelength-division multiplexing systems.