High-speed directly modulated widely tunable two-section InGaAlAs DBR lasers

Area of Science:

• Optoelectronics
• Semiconductor Lasers
• Materials Science

Background:

• Distributed Bragg Reflector (DBR) lasers are crucial for tunable light sources.
• Optimizing gain materials and DBR sections is key to enhancing laser performance.
• Temperature stability and modulation bandwidth are critical parameters for laser applications.

Purpose of the Study:

• To investigate the performance of widely tunable two-section DBR lasers utilizing InGaAlAs multiple quantum wells (MQWs).
• To compare the characteristics of InGaAlAs-based DBR lasers with traditional InGaAsP DBR lasers.
• To evaluate the impact of DBR current injection on wavelength tuning, modulation bandwidth, and side mode suppression ratio (SMSR).

Main Methods:

• Fabrication of two-section DBR lasers with InGaAlAs MQWs as the gain medium.
• Integration of an InGaAsP material (photoluminescence wavelength 1.4 μm) for the DBR section.
• Characterization of wavelength tuning range via current injection into the DBR section.
• Measurement of direct modulation bandwidth and side mode suppression ratio (SMSR) across the tuning range and temperature variations.

Main Results:

• Achieved a wavelength tuning range of 12 nm through current injection into the DBR section.
• Demonstrated direct modulation bandwidth exceeding 10 GHz across the entire tuning range, even up to 40°C.
• Observed significantly smaller variations in threshold current and slope efficiency with temperature for InGaAlAs lasers compared to InGaAsP lasers, attributed to better electron confinement.
• Reported notably smaller decreases in modulation bandwidth and SMSR due to DBR current injection for InGaAlAs lasers versus InGaAsP lasers.

Conclusions:

• InGaAlAs MQWs offer superior temperature stability and electron confinement in DBR lasers compared to InGaAsP.
• The developed InGaAlAs DBR lasers provide a wider tuning range and maintain high modulation bandwidth and SMSR under DBR current injection.
• These findings highlight the potential of InGaAlAs-based DBR lasers for advanced optoelectronic applications requiring tunable and stable light sources.