Characterization of a multifunctional active demultiplexer for optical frequency combs

• Published in: Optics and laser technology 2021-02, Vol.134, p.106637, Article 106637
• Main Authors: Lakshmijayasimha, Prajwal D., Kaszubowska-Anandarajah, Aleksandra, Martin, Eamonn P., Hammad, Mohab N., Landais, Pascal, Anandarajah, Prince M.
• Format: Article
• Language: English
• Subjects: Active demultiplexer; Amplification; Demultiplexers; Demultiplexing; Frequency drift; Frequency locking; Gain; Gain-switched lasers; Injection locking; Optical frequency; Optical frequency comb
• ISSN: 0030-3992; 1879-2545
• DOI: 10.1016/j.optlastec.2020.106637

•Active demultiplexer solution for optical frequency combs especially with low-FSR.•Multifunctional device: demultiplexer, ultra-low noise amplifier, and gain-equalizer.•Flexible: demultiplexing of frequency combs with arbitrary FSR (from 1.25 to 15 GHz).•Photonically integratable architecture: offers smaller footprint and lower cost. We report on a multifunctional active demultiplexer for optical frequency combs. The proposed technique, based on injection locking, combines the functionality of a tunable demultiplexer, gain equalizer and an optical amplifier, all in one device. Validation of the concept is experimentally demonstrated through simultaneous demultiplexing and amplification of combs with various free spectral ranges (2.5 to 15 GHz), achieving an adjacent channel suppression ratio > 35 dB and an output power of 7.5 dBm. The functionality of the demultiplexer is extended to that of a gain equalizer, by filtering comb tones with powers 10 dB below the spectral peak, whilst maintaining a suppression ratio > 30 dB and a constant output power. This feature increases the number of comb lines suited for data modulation (i.e. usable lines), by a factor of ~1.7. Finally, we test the stability of such a demultiplexer, by measuring the frequency drift, beat tone power variations and phase correlation between demultiplexed tones.