Efficient and low-noise single-photon-level frequency conversion interfaces using silicon nanophotonics (1510.02527v1)

Abstract: Optical frequency conversion has applications ranging from tunable light sources to telecommunications-band interfaces for quantum information science. Here, we demonstrate efficient, low-noise frequency conversion on a nanophotonic chip through four-wave-mixing Bragg scattering in compact (footprint < 0.5 x 10^-4 cm^2) Si3N4 microring resonators. We investigate three frequency conversion configurations: (1) spectral translation over a few nanometers within the 980 nm band, (2) upconversion from 1550 nm to 980 nm, and (3) downconversion from 980 nm to 1550 nm. With conversion efficiencies ranging from 25 % for the first process to > 60 % for the last two processes, a signal conversion bandwidth > 1 GHz, < 60 mW of continuous-wave pump power needed, and background noise levels between a few fW and a few pW, these devices are suitable for quantum frequency conversion of single photon states from InAs quantum dots. Simulations based on coupled mode equations and the Lugiato-Lefever equation are used to model device performance, and show quantitative agreement with measurements.

• The paper demonstrates low-noise, efficient frequency conversion at the single-photon level using Si₃N₄ microring resonators in a compact design.
• It employs four-wave mixing Bragg scattering in intraband, upconversion, and downconversion configurations to achieve conversion efficiencies from 25% to over 60% at pump powers below 60 mW.
• Numerical simulations based on coupled mode equations and modified Lugiato-Lefever models corroborate experimental results, underscoring the technique's potential for scalable quantum photonic systems.

Overview of Single-Photon-Level Frequency Conversion Interfaces Using Silicon Nanophotonics

The paper presents advancements in the field of optical frequency conversion using silicon nanophotonics. It particularly focuses on the application of low-noise, efficient frequency conversion at the single-photon level, which is critical for both classical photonics and quantum information science applications. The authors demonstrate a frequency conversion mechanism using silicon nitride ($\text{Si}_3\text{N}_4$) microring resonators to efficiently translate optical signals between wavelengths.

Experimental Setup and Results

The paper investigates frequency conversion across three configurations: intraband conversion within the 980 nm band, upconversion from the telecommunication band (1550 nm) to the 980 nm band, and downconversion from the 980 nm to the 1550 nm band. The experimental approach harnesses four-wave-mixing Bragg scattering (FWM-BS), which is operationalized through these microring resonators with high quality factors and demonstrated conversion efficiencies ranging from 25% to over 60%.

Significantly, these devices achieve such conversion efficiencies at pump powers below 60 mW, with background noise levels between a few femtowatts to a few picowatts, making them suitable for quantum frequency conversion (QFC) of single-photon states, notably for use with quantum dot emitters.

Numerical Simulations and Theoretical Modeling

To model and predict device performance, the authors employed numerical simulations based on coupled mode equations and modifications to the Lugiato-Lefever equation specific to the FWM-BS process. The simulations provide insights into the frequency conversion process's efficiency and noise characteristics, corroborating the experimental results.

Implications and Future Work

The demonstrated frequency conversion interfaces are notable for their compact design and low power requirements, properties that are crucial for their integration into scalable quantum photonic systems. The ability to convert frequencies with a controllable spectral translation is pertinent for both classical multiplexing and bridging gaps between dissimilar quantum systems at varying operational wavelengths.

Future advancements could focus on extending the operational bandwidth and investigating methods for quelling the background noise further, a critical factor for quantum applications. Improvements in material quality, such as reduced microscale absorption, could enhance device performance. Furthermore, there is a potential to explore these devices' utility in telecommunications, particularly where integration with existing optical fiber infrastructures is desired.

These findings open pathways to interface various quantum light sources with telecommunications bands and highlight the potential of silicon nanophotonics as versatile platforms for routing and manipulating quantum information at the photonic level.