12.5 Gbit/s directly modulated InAs/GaAs quantum dot lasers grown on Si (001) substrate with strong optical feedback...

Area of Science:

• Materials Science
• Optoelectronics
• Semiconductor Physics

Background:

• Silicon photonics offers a low-cost, scalable platform for integrated circuits.
• Directly modulated lasers are crucial for high-speed optical communication.
• Quantum dot (QD) lasers grown on silicon substrates are highly desirable but challenging.

Purpose of the Study:

• To demonstrate a high-performance directly modulated InAs/GaAs quantum dot (QD) laser epitaxially grown on a Si (001) substrate.
• To investigate the laser's operational characteristics, including continuous-wave (CW) performance, modulation bandwidth, and optical feedback resistance.
• To assess the potential of these QD lasers for silicon photonics integrated circuits (PICs).

Main Methods:

• Epitaxial growth of InAs/GaAs quantum dots on a Si (001) substrate.
• Fabrication of a ridge waveguide laser structure (3×600 µm²).
• Characterization using continuous-wave (CW) operation, small-signal modulation, non-return-to-zero (NRZ) large-signal modulation, and dynamic optical feedback measurements.

Main Results:

• Achieved 12.5 Gbit/s modulation rate at room temperature (RT).
• Demonstrated CW operation from 25°C to 75°C with a maximum output power of 16.9 mW at RT.
• Exhibited strong optical feedback tolerance with a low bit error ratio (BER) of 6×10⁻⁶ at -9 dB feedback intensity.
• Measured 3 dB bandwidth of 3.8 GHz at 25°C and 2.7 GHz at 55°C.

Conclusions:

• The developed InAs/GaAs QD laser on Si (001) shows excellent performance and strong optical feedback resistance.
• These lasers are suitable for high-speed, isolator-free silicon photonics applications.
• The results highlight the potential for large-scale, low-cost silicon photonics integrated circuits.