分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： 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.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： We characterize the frequency response of channel-interleaved photonic analog-to-digital converters (CI-PADCs) theoretically and experimentally. The CI-PADC is composed of a photonic frontend for photonic sampling and an electronic backend for quantization. The photonic frontend includes a photonic sampling pulse generator for directly high-speed sampling and an optical time-division demultiplexer (OTDM) for channel demultiplexing. It is found that the frequency response of the CI-PADC is influenced by both the photonic sampling pulses and the OTDM, of which the combined impact can be characterized through demultiplexed pulse trains. First, the frequency response can be divided into multiple frequency intervals and the range of the frequency interval equals the repetition rate of demultiplexed pulse trains. Second, the analog bandwidth of the CI-PADC is determined by the optical spectral bandwidth of demultiplexed pulse trains which is broadened in the OTDM. Further, the effect of the OTDM is essential for enlarging the analog bandwidth of the CI-PADC employing the photonic sampling pulses with a limited optical spectral bandwidth.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Erbium-doped lithium niobate on insulator (Er:LNOI) is a promising platform for photonic integrated circuits as it adds gain to the LNOI system and enables on-chip lasers and amplifiers. A challenge for Er:LNOI laser is to increase its output power while maintaining single-frequency and single (-transverse)-mode operation. In this work, we demonstrate that single-frequency and single-mode operation can be achieved even in a single multi-mode Er:LNOI microring by introducing mode-dependent loss and gain competition. In a single microring with a free spectral range of 192 GHz, we have achieved single-mode lasing with an output power of 2.1 microwatt, a side-mode suppression of 35.5 dB, and a linewidth of 1.27 MHz.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： 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.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： We report on the realization of a long-haul radio frequency (RF) transfer scheme by using multiple-access relay stations (MARSs). The proposed scheme with independent link noise compensation for each fiber sub-link effectively solves the limitation of compensation bandwidth for long-haul transfer. The MARS can have the capability to share the same modulated optical signal for the front and rear fiber sub-links, simplifying the configuration at the repeater station and enabling the transfer system to have the multiple-access capability. At the same time, we for the first time theoretically model the effect of the MARS position on the fractional frequency instability of the fiber-optic RF transfer, demonstrating that the MARS position has little effect on system's performance when the ratio of the front and rear fiber sub-links is around $1:1$. We experimentally demonstrate a 1 GHz signal transfer by using one MARS connecting 260 and 280 km fiber links with the fractional frequency instabilities of less than $5.9\times10^{-14}$ at 1 s and $8.5\times10^{-17}$ at 10,000 s at the remote site and of $5.6\times10^{-14}$ and $6.6\times10^{-17}$ at the integration times of 1 s and 10,000 s at the MARS. The proposed scalable technique can arbitrarily add the same MARSs in the fiber link, which has great potential in realizing ultra-long-haul RF transfer.
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