Cryogenic-compatible ultrahigh rejection and narrowband sinusoidal Bragg filter for integrated quantum photonics

Area of Science:

• Quantum Photonics
• Cryogenic Engineering
• Nanophotonics

Background:

• Cryogenic environments are ideal for integrated quantum photonic systems due to low noise and component compatibility.
• High-performance on-chip optical filters are essential for isolating single photons from pump light in nonlinear processes.
• Existing filters often lack the necessary performance for demanding cryogenic quantum applications.

Purpose of the Study:

• To develop and demonstrate a cryogenic-compatible optical filter for integrated quantum photonic circuits.
• To achieve ultrahigh rejection and narrowband filtering for efficient single-photon extraction.
• To suppress background noise in cryogenic quantum photonic systems.

Main Methods:

• Designed a Bragg filter with a sinusoidal coherency-broken cascaded architecture.
• Incorporated subwavelength gratings to mitigate transverse magnetic mode photons.
• Utilized a niobium nitride film as a light absorption layer for noise suppression.

Main Results:

• Achieved an 82 dB rejection ratio at room temperature and 76 dB at 2.2 K.
• Demonstrated narrow bandwidths of 0.9 nm at room temperature and 0.8 nm at 2.2 K.
• Confirmed the filter's suitability for cryogenic operation.

Conclusions:

• The developed Bragg filter meets the stringent requirements for cryogenic integrated quantum photonic circuits.
• This filter technology provides essential support for advancing cryogenic quantum information processing.
• The design offers a pathway to enhanced performance in low-noise quantum optical systems.