Free-space point-to-multiplepoint optical frequency transfer with lens assisted integrated beam steering

TL;DR

This paper demonstrates a novel lens-assisted beam-steering array enabling high-precision, multi-user free-space optical frequency transfer over 50 meters with low phase noise, advancing integrated optical communication and timing systems.

Contribution

It introduces a 2D LABS array capable of supporting up to 16 simultaneous links with simplified control, and achieves ultra-stable frequency transfer over significant distances.

Findings

Supports up to 16 simultaneous user nodes.

Achieves fractional frequency instability of 4.5×10⁻¹⁷ at 1 s.

Demonstrates stable transfer over 50 meters.

Abstract

We report on the realization of high-performance silica integrated two-dimensional lens assisted beam-steering (LABS) arrays along with the first-of-their-kind point-to-multiplepoint optical frequency transfer. {The LABS equips with $N$ antennas} and has the capability to produce arbitrary number of output beams with different output angles with the simple control complexity. We demonstrate that the LABS has 16 scanning angles, which can support {the access capability for the maximum of simultaneous 16 user nodes.} The coaxial configuration for transmitting and receiving the light as a monolithic transceiver allows us to reduce the out-of-loop phase noise significantly. Finally, the LABS-based non-blocking point-to-multiplepoint in-door free-space optical frequency transfer links with 24 m and 50 m free-space links are shown. After being compensated for the free-space link up to 50 m, the fractional frequency instability of $4.5\times10^{-17}$ and $7.7\times10^{-20}$ at the averaging time of 1 s and 20,000 s, respectively, can be achieved. The present work proves the potential application of the 2D LABS in free-space optical time-frequency transfer and provides a guidance for developing a chip-scale optical time-frequency transfer system.