Demonstration of InP-on-Si Self-Pulsating DFB Laser Diodes for Optical Microwave Generation

45 Gb/s Direct Modulation of Two-Section InP-on-Si DFB Laser Diodes

“…The laser structure was used previously to demonstrate selfpulsating laser diodes [3]. The two sections are designed to have different mesa width to obtain a difference in effective index, and thereby to control the spacing of the stop bands.…”

“…As the bonding layer thickness is very small (less than 10 nm), the silicon grating coupling is strong. The stop-band of each laser section is not clearly identified, but from characterization it is expected that each section has as stopband of around 5 nm [3] with the extracted coupling coefficient κ being ~ 150 cm -1 . This high coupling coefficient is the source of the multimode behavior observed in the spectrum.…”

“…4, which are separated by around 20 GHz (≈ 0.15 nm). If both modes are of similar strengths, there will be beating around the frequency difference [3]. As a result, the second resonance would be too strong and would lead to too strong distortion.…”

“…Therefore, the side-mode should be sufficiently weaker than the main mode, for the second resonance to be within the 3-dB small signal modulation range. As shown in [3], it is possible to tune the separation between the peaks, which controls the frequency at which the second resonance occurs, to fine tune the small signal modulation. Data transmission experiments were conducted to investigate the large signal modulation of the laser.…”

“…For example, for wavelength tuning, discrete wavelength tuning over 55 nm was demonstrated using sampled DFB gratings [2]. As for radioover-fiber applications, self-pulsating laser diodes with controlled frequency between 10 and 40 GHz were demonstrated using two-section DFB laser diodes [3]. Finally, for datacom applications, high-speed DFB laser diodes were recently demonstrated at 56 Gbps with direct modulation and 2 x 56 Gbps with electro-absorption modulation [4,5].…”