Effects of active section length on directly modulated 1.3 µm InGaAlAs/InP DFB lasers with a MQW-based passive DBR...

Area of Science:

• Optoelectronics
• Semiconductor Lasers
• Fiber Optic Communications

Background:

• Distributed feedback (DFB) lasers are crucial for optical communication systems.
• Integrated passive distributed Bragg reflector (DBR) sections simplify fabrication.
• Understanding current self-heating effects is vital for optimizing laser performance.

Purpose of the Study:

• To fabricate directly modulated 1.3µm InGaAlAs/InP DFB lasers with MQW-based passive DBR sections.
• To investigate the impact of DFB section length on device performance, focusing on self-heating effects.
• To demonstrate high-speed data transmission capabilities.

Main Methods:

• Fabrication of InGaAlAs/InP DFB lasers with integrated MQW DBR sections.
• Comparison of lasers with 150 µm and 200 µm DFB lengths.
• Characterization of optical spectra, side mode suppression ratio (SMSR), and modulation bandwidth.
• Testing of 50 Gb/s NRZ and PAM4 data transmission over 40 km SMF.

Main Results:

• Devices with identical MQWs in DFB and DBR sections simplify fabrication.
• A 200 µm DFB section yields a higher modulation bandwidth (29 GHz) compared to a 150 µm section.
• The longer DFB section shows less sensitivity to current-induced wavelength shift due to self-heating.
• Successful 50 Gb/s NRZ and PAM4 transmission demonstrated up to 40 km at 25°C and 50°C.

Conclusions:

• DFB laser design with integrated MQW DBR sections is effective for simplified fabrication.
• Longer DFB sections improve direct modulation bandwidth and data transmission performance.
• The fabricated lasers are suitable for high-speed, long-distance optical communication applications.