Integrated Si₃N₄ microresonator-based quantum light sources with high brightness using a subtractive wafer-scale...

Area of Science:

• Integrated quantum photonics
• Materials science for photonics
• Quantum optics

Background:

• Silicon nitride (Si3N4) offers advantages over silicon for integrated quantum photonics due to moderate optical nonlinearity and low optical loss.
• Developing wafer-scale, crack-free, thick Si3N4 films using CMOS-compatible processes for quantum light sources remains a challenge.

Purpose of the Study:

• To demonstrate a unique subtractive fabrication process for a high-quality, thick silicon nitride platform.
• To enable the development of dispersion-engineered quantum light sources on chip.

Main Methods:

• Introduction of a stress-release pattern before single Si3N4 film deposition.
• Fabrication of 950 nm-thick, 8 μm-wide microring resonators supporting whispering-gallery modes.
• Characterization of photon-pair generation rate, spectral brightness, and heralded single-photon measurements.

Main Results:

• Achieved a high photon-pair generation rate of approximately 1.03 MHz/mW².
• Reported a high spectral brightness of approximately 5×10⁶ pairs/s/mW²/GHz.
• Demonstrated the first heralded single-photon measurement on a Si3N4 platform with a high-quality conditional self-correlation gH⁽²⁾(0) of 0.008 ± 0.003.

Conclusions:

• The developed subtractive fabrication process enables high-performance silicon nitride integrated photonic circuits.
• The Si3N4 platform is suitable for creating efficient quantum light sources, including heralded single-photon sources.
• This work paves the way for advanced quantum photonic applications using silicon nitride.