Heterogeneous quantum dot lasers on low-confinement silicon nitride with reduced-bending architecture

Area of Science:

• Photonics and Optical Engineering
• Materials Science
• Semiconductor Lasers

Background:

• Silicon nitride (SiN) waveguides offer ultra-low optical losses but typically require large bend radii.
• Integrating SiN into heterogeneous lasers necessitates strategies to manage footprint and optical losses.
• Existing laser designs may not fully leverage the low-loss properties of SiN for compact devices.

Purpose of the Study:

• To demonstrate a compact heterogeneous laser utilizing silicon nitride waveguides.
• To overcome the wide bend radius limitation of SiN for small-footprint devices.
• To achieve high performance metrics including low threshold current, high output power, and narrow linewidth.

Main Methods:

• Fabrication of heterogeneous quantum dot lasers on SiN waveguides.
• Employment of metal-coated etched facets and transversely coupled Fabry-Perot resonators as mirrors.
• Integration of on-chip facets, adiabatic taper couplers, and distributed Bragg reflectors (DBRs).

Main Results:

• Achieved threshold current densities below 250 A/cm².
• Measured output power exceeding 15 mW in an integrating sphere.
• Observed a laser linewidth narrower than 5 MHz.
• Demonstrated a total device footprint of less than 1 mm².

Conclusions:

• The developed heterogeneous laser effectively utilizes silicon nitride waveguides for high performance in a compact form factor.
• Metal-coated etched facets and coupled resonators provide an effective mirroring solution for SiN-based lasers.
• The device shows promise for applications requiring low-loss, high-power, and narrow-linewidth lasers in a small footprint.