Monolithic photonic chips for multi-channel frequency mixers and single photon detectors

TL;DR

This paper presents a monolithic lithium niobate photonic chip capable of multi-channel sum-frequency conversion and single-photon detection, demonstrating high efficiency, low noise, and excellent channel isolation for advanced optical applications.

Contribution

The work introduces a robust, fiber-coupled monolithic photonic chip with uniform multi-channel sum-frequency conversion and integrated single-photon detection, advancing integrated quantum and optical communication technologies.

Findings

Average detection efficiency of 23.2% across 30 channels

Noise count rate of 557 cps with low variation

Optical isolation exceeding 71 dB between channels

Abstract

Lithium niobate photonic chip could realize diverse optical engineering for various applications benefiting from its excellent optical performances. In this letter, we demonstrate monolithic photonic chips for multi-channel sum-frequency conversion based on reverse-proton-exchange periodically poled lithium niobate waveguides, with the different channels showing uniform and excellent conversion efficiencies. To obtain a robust device and provide a convenient interface for applications, the integrated chip is fiber coupled with two fiber arrays. The packaged chip then forms the core of a multi-channel up conversion single photon detector. In each channel the input signal interacts with a 1950-nm single frequency pump laser and the sum frequency output is spectrally filtered and detected by a silicon avalanche photodiode. Average detection efficiency (DE) of 23.2 % and noise count rate (NCR) of 557 counts per second (cps) are achieved, with a standard deviation of 2.73 % and 48 cps over the 30 channels, as well as optical isolation (OI) between nearby channels of more than 71 dB, which are excellent for the extensive applications of monolithic photonic chips in fields including deep space laser communication, high-rate quantum key distribution and single-photon imaging.