Subjects: Optics >> Quantum optics submitted time 2023-02-19
Abstract： We present a technique for coherence transfer of laser light through a branching fiber link, where the optical phase noise induced by environmental perturbations via the fiber link is passively compensated by remote users without the requirements of any active servo components. At each remote site, an acousto-optic modulator (AOM) is simultaneously taken as a frequency distinguisher for distinguishing its unique frequency from other sites' and as an optical actuator for compensating the phase noise coming from the optical fiber. With this configuration, we incorporate a long outside loop path consisting of a fiber-pigtailed AOM into the loop, enabling the significant reduction of the outside loop phase noise in the passive way. To further address the residual out-of-loop phase noise coming from the interferometer and the two-way optical frequency comparison setup, we design a low-noise active temperature stabilization system. Measurements with a back-to-back system show that the stability in our stabilization system is $2\times10^{-16}$ at 1 s, reaching $2\times10^{-20}$ after 10,000 s. Adopting these techniques, we demonstrate transfer of a laser light through a branching fiber network with 50 km and 145 km two fiber links. After being compensated for the 145 km fiber link, the relative frequency instability is $3.4\times10^{-15}$ at the 1 s averaging time and scales down to $3.7\times10^{-19}$ at the 10,000 s averaging time. This proposed technique is suitable for the simultaneous transfer of an optical signal to a number of independent users within a local area.
Peer Review Status:
Awaiting Review
Subjects: Optics >> Quantum optics submitted time 2023-02-19
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.
Peer Review Status:Awaiting Review
Subjects: Optics >> Quantum optics submitted time 2023-02-19
Abstract： High-stability optical frequency comparison over fiber link enables the establishment of ultrastable optical clock networks, having the potential to promote a series of applications, including metrology, geodesy, and astronomy. In this article, we theoretically analyze and experimentally demonstrate a timedelayed local two-way (TD-LTW) optical frequency comparison scheme with improved comparison stability, showing that the fractional instability of optical frequency comparison over a 50- km transfer link can be reduced from $1.30\times10^{-15}$ to $5.25\times10^{-16}$ at the 1 s integration time with an improvement factor of 2.48. Additionally, we also for the first time model and experimentally verify the effect of the inhomogeneous phase noise along the fiber link on the system performance. We believe that the theory and technique proposed here will be helpful in developing the high-stability optical clock networks over large-area fiber links.
Peer Review Status:Awaiting Review
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