Unidirectional emission of GaN-based eccentric microring laser with low threshold

Area of Science:

• Optics and Photonics
• Materials Science

Background:

• Whispering gallery mode (WGM) microcavities are crucial for laser applications.
• Achieving low lasing thresholds and unidirectional emission in microcavities remains a challenge.

Purpose of the Study:

• To propose and demonstrate a novel GaN-based eccentric microring structure.
• To reduce the lasing threshold and achieve unidirectional emission in WGM microcavities.

Main Methods:

• Fabrication of an eccentric microring with an off-center inner hole in Gallium Nitride (GaN).
• Characterization of lasing properties, including threshold, unidirectionality, and Q factor.
• Finite-difference time-domain (FDTD) numerical simulations to analyze field distribution and far-field profiles.

Main Results:

• The eccentric microring demonstrated a reduction in lasing threshold by up to 53% compared to a microdisk.
• High unidirectionality of laser emission was achieved with a far-field divergence angle of approximately 40°.
• A high Q factor of 6388 was maintained for the whispering gallery modes.
• FDTD simulations confirmed that hole position and size control the far-field emission profile.

Conclusions:

• The eccentric microring structure significantly enhances the performance of WGM microcavity lasers.
• This simple yet effective design offers important guidance for developing advanced microcavity lasers.
• The ability to control far-field emission through structural modifications opens new avenues for laser design.