70 dB long-pass filter on a nanophotonic chip

Area of Science:

• Quantum information science
• Integrated photonics
• Optical filter technology

Background:

• Scalable quantum information processing relies on integrated quantum photonic chips.
• On-chip integration of quantum sources and detectors is limited by background photons from pump light.
• Existing methods struggle to effectively suppress strong classical pump light on-chip.

Purpose of the Study:

• To design and fabricate an on-chip long-pass filter for integrated quantum photonic circuits.
• To achieve high attenuation of visible pump light while maintaining low loss for telecom-band signals.
• To enable monolithic integration of quantum sources, filters, and detectors on a single chip.

Main Methods:

• Designed an on-chip adiabatic long-pass filter.
• Fabricated the filter on a material system compatible with spontaneous parametric down-conversion sources.
• Characterized the filter's performance in terms of attenuation and insertion loss.

Main Results:

• The fabricated filter provides 70 dB attenuation for visible light near 775 nm.
• The filter exhibits less than 3 dB insertion loss for light in the telecom C-band near 1550 nm.
• The adiabatic design ensures broadband operation and robustness against fabrication variations.

Conclusions:

• The on-chip long-pass filter effectively suppresses background pump light.
• This filter, combined with on-chip quantum sources, allows for 100 dB pump light suppression.
• The developed platform is promising for realizing fully integrated quantum photonic chips.