Broadband Quantum Dot Superluminescent Diode with Simultaneous Three-State Emission

Area of Science:

• Optoelectronics
• Materials Science
• Quantum Dot Technology

Background:

• Semiconductor superluminescent light-emitting diodes (SLEDs) are crucial broadband light sources for applications in sensing, imaging, and optical systems.
• Self-assembled quantum dots (SAQDs) offer intrinsic spectral broadening for SLEDs, but typically limited to ground state (GS) or GS and first excited state (ES1) emission.
• Expanding emission to higher excited states (ESs) is key to achieving wider spectral bandwidths in quantum dot (QD) SLEDs.

Purpose of the Study:

• To engineer a broadband quantum dot SLED capable of simultaneous emission from multiple energy states (GS, ES1, and ES2).
• To enhance the spectral width and output power of QD-based SLEDs beyond current limitations.
• To establish a new fabrication technique for high-performance QD-based low-coherent light sources.

Main Methods:

• Optimized molecular beam epitaxy (MBE) to grow multiple five-QD-layer structures with large, inhomogeneously distributed dot sizes.
• Developed a precise mirror-coating process to independently control cavity mirror loss for GS and ES emissions.
• Fabricated and characterized the broadband QD-SLED, analyzing its spectral width, spectral dip, and continuous wave (CW) output power.

Main Results:

• Successfully realized a broadband QD-SLED exhibiting simultaneous emission from GS, ES1, and ES2.
• Achieved a large spectral width of 91 nm with a minimal spectral dip of 1.3 dB.
• Demonstrated a high continuous wave (CW) output power of 40 mW.

Conclusions:

• The developed QD-SLED architecture effectively leverages multiple excited states for broadband emission.
• The optimized MBE growth and mirror-coating techniques enable enhanced performance in QD-based SLEDs.
• This work presents a promising fabrication approach for advanced QD-based low-coherent light sources.