High external feedback resistance of laterally loss-coupled distributed feedback quantum dot semiconductor lasers

• Published in: IEEE photonics technology letters Vol. 15; no. 11; pp. 1504 - 1506
• Main Authors: Su, H., Zhang, L., Gray, A.L., Wang, R., Newell, T.C., Malloy, K.J., Lester, L.F.
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.11.2003; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Distributed feedback devices; Electrical resistance measurement; Feedback; Laser feedback; Lasers; Modulation; Noise levels; Optical feedback; Optical losses; Optical modulation; Quantum dot lasers; Quantum dots; Quantum wells; Semiconductor lasers; Signal resolution; Spectra; Spectral analysis
• ISSN: 1041-1135; 1941-0174
• DOI: 10.1109/LPT.2003.818627

External optical feedback effects on quantum dot (QD) laterally loss-coupled (LLC) distributed feedback (DFB) lasers are reported for the first time in this letter. The critical external feedback ratio that causes coherence collapse of the QD DFB is measured to be -14 dB. No spectral broadening at this feedback level is observed within the 0.06-nm resolution of the optical spectrum analyzer (OSA). Self-homodyne measurements also confirm that the rebroadened linewidth of the QD DFB under -14-dB feedback is still much smaller than the feedback-free linewidth. Under 2.5-Gb/s modulation, eye-diagram measurements show that the signal-to-noise ratio starts to degrade at a feedback ratio of -30 dB in the QD LLC-DFB, about 20 dB higher than a typical quantum-well DFB at the same output power and extinction ratio.