Ultra-compact and low-threshold thulium microcavity laser monolithically integrated on silicon

Area of Science:

• Photonics and Optical Engineering
• Materials Science
• Integrated Optics

Background:

• Silicon photonics is a rapidly advancing field for integrated optical circuits.
• Thulium-doped materials are essential for lasers operating in the 2-micron wavelength range.
• On-chip laser integration faces challenges in miniaturization and efficiency.

Purpose of the Study:

• To demonstrate an ultra-compact and low-threshold thulium microcavity laser monolithically integrated on a silicon chip.
• To enable efficient on-chip pump input and laser output coupling.
• To explore the potential of on-chip thulium lasers for silicon microphotonic systems.

Main Methods:

• Fabrication of a thulium-doped aluminum oxide microcavity monolithically integrated with a silicon nitride bus waveguide.
• Characterization of lasing performance under resonant pumping at 1.6 μm.
• Analysis of lasing wavelength, threshold power, and slope efficiency at varying waveguide-microcavity gap sizes.

Main Results:

• Observation of lasing in the 1.8-1.9 μm wavelength range.
• Achieved a low threshold power as low as 773 μW (226 μW).
• Demonstrated high slope efficiency up to 24% (48%) with respect to coupled pump power.

Conclusions:

• The integrated thulium microcavity laser is ultra-compact and operates with low threshold and high efficiency.
• The silicon nitride waveguide enables efficient on-chip coupling for pump input and laser output.
• This silicon-compatible thulium laser is a promising light source for advanced silicon microphotonic systems.