Down-converted photon pairs in a high-Q silicon nitride microresonator

Area of Science:

• Quantum Optics
• Materials Science
• Integrated Photonics

Background:

• Entangled photon pairs from spontaneous parametric down-conversion (SPDC) are crucial for quantum applications.
• SPDC traditionally requires non-centrosymmetric materials with second-order nonlinearity (χ(2)).
• Silicon nitride (Si3N4) is ideal for integrated photonics due to low loss but lacks intrinsic χ(2).

Purpose of the Study:

• To demonstrate strong narrowband SPDC in silicon nitride (Si3N4).
• To overcome the lack of intrinsic nonlinearity in amorphous Si3N4 for quantum applications.
• To develop a high-brightness entangled photon source based on Si3N4 integrated photonics.

Main Methods:

• Utilized spontaneous parametric down-conversion (SPDC) in a silicon nitride (Si3N4) platform.
• Combined strong light-field enhancement within a high Q-factor microcavity.
• Employed an optically induced space-charge field to enable nonlinear interaction.

Main Results:

• Achieved strong narrowband SPDC with an on-chip rate of 0.8 million pairs per second.
• Generated photon pairs with high spectral brightness.
• Verified the quantum nature of the generated photon pairs through coincidence measurements.

Conclusions:

• Demonstrated a viable method for SPDC in silicon nitride (Si3N4) by overcoming its amorphous nature.
• Established a high-performance entangled photon source leveraging Si3N4 integrated photonics.
• Unlocked new possibilities for on-chip quantum systems using a low-loss material.