Blue Lasing at Room Temperature Based on a Quasi-Bound State in the Continuum.

Area of Science:

• Optoelectronics
• Materials Science
• Photonics

Background:

• Gallium nitride (GaN)-based materials are crucial for optoelectronic devices.
• Achieving efficient blue lasing at room temperature remains a challenge.
• Subwavelength gratings offer unique optical properties for light manipulation.

Purpose of the Study:

• To demonstrate room-temperature lasing in the blue spectral range (440-460 nm).
• To utilize indium gallium nitride (InGaN) quantum wells coupled to quasi-bound states in the continuum (quasi-BICs).
• To develop compact and tunable monolithic GaN-based photonic devices.

Main Methods:

• Designing and fabricating monolithic GaN-based subwavelength gratings with sub-10 nm precision.
• Employing electrochemical etching to create a nanoporous GaN layer for substrate mode suppression.
• Utilizing e-beam lithography and dry etching for high-precision fabrication.
• Confirming quasi-BICs through angle-resolved reflectivity and polarization vortex observation.

Main Results:

• Demonstrated room-temperature blue lasing (440-460 nm) with InGaN quantum wells.
• Achieved a low lasing threshold of 0.16 mJ cm^-2 pulse^-1.
• Observed a narrow spectral bandwidth (<0.04 nm) and strongly linearly polarized emission.
• Confirmed efficient tunability of the lasing wavelength by adjusting grating geometry.

Conclusions:

• Successfully demonstrated room-temperature blue lasing using InGaN quantum wells coupled to quasi-BICs in GaN subwavelength gratings.
• The integration of a nanoporous GaN layer effectively suppresses substrate leakage.
• The developed structures offer a promising platform for compact, tunable, and efficient monolithic GaN-based photonic devices.