Compact high-extinction tunable CROW filters for integrated quantum photonic circuits

Area of Science:

• Photonics
• Quantum Optics
• Integrated Optics

Background:

• Spontaneous four-wave mixing (SFWM) is a key process for generating quantum-correlated photons.
• Efficiently filtering out strong pump photons is crucial for detecting these generated photons.
• Existing filtering techniques often lack the required extinction ratios or compactness.

Purpose of the Study:

• To demonstrate the effectiveness of cascaded second-order coupled-resonator optical waveguide (CROW) tunable filters for high-extinction ratio filtering.
• To utilize these filters for pump photon removal in SFWM experiments.
• To assess the suitability of CROW filters for integrated quantum photonic circuits.

Main Methods:

• Fabrication and characterization of cascaded second-order CROW tunable filters.
• Integration of CROW filters with a silicon waveguide for SFWM experiments.
• Measurement of extinction ratios and detection of quantum-correlated photons post-filtering.

Main Results:

• Achieved measured extinction ratios greater than 110 dB, among the highest reported.
• Successfully suppressed pump photons from the SFWM process.
• Enabled the measurement of quantum-correlated photons generated via SFWM.

Conclusions:

• Cascaded second-order CROW tunable filters provide exceptional extinction ratios for quantum optics applications.
• These filters are highly effective for isolating quantum-correlated photons from pump light in SFWM.
• The compact nature of CROW filters makes them suitable for monolithic quantum photonic integrated circuits.