Narrow linewidth VCSEL based on resonant optical feedback from an on-chip microring add-drop filter

Area of Science:

• Photonics and Optical Engineering
• Semiconductor Lasers
• Nanophotonics

Background:

• Vertical-cavity surface-emitting lasers (VCSELs) are crucial optoelectronic devices.
• Achieving narrow linewidth and frequency stability in VCSELs is essential for high-performance applications.
• Existing methods for linewidth reduction often involve complex external cavities.

Purpose of the Study:

• To demonstrate a narrow linewidth VCSEL by incorporating resonant optical feedback.
• To investigate the effectiveness of an on-chip microring add-drop filter for spectral purification.
• To analyze the impact of thermo-optic effects on laser frequency stabilization.

Main Methods:

• Injecting resonant optical feedback into the VCSEL cavity.
• Utilizing an on-chip microring add-drop filter with a high quality factor (1.36 million).
• Experimentally controlling the optical feedback level to -47.77 dB.

Main Results:

• A single longitudinal mode VCSEL with a Lorentzian linewidth of 32.6 kHz was achieved.
• A purified optical spectrum was obtained due to the microring filter.
• The thermo-optic effect in the microring resonator contributed to lasing frequency stabilization.

Conclusions:

• Optical feedback is an effective method for significantly reducing VCSEL linewidth.
• On-chip microring resonators can act as efficient filters for spectral purification.
• The demonstrated narrow linewidth and stable frequency VCSEL is suitable for advanced optical systems.