Integrated optomechanical crystal (OMC) cavities provide a vital device prototype for highly efficient microwave to optical conversion in quantum information processing. In this work, we propose a novel heterogeneous OMC cavity consisting of a thin-film lithium niobate (TFLN) slab and chalcogenide (ChG) photonic crystal nanobeam coupled by a wavelength-scale mechanical waveguide. The optomechanical coupling rate of the heterogeneous OMC cavity is optimized up to 340 kHz at 1.1197 GHz. Combined with phononic band and power decomposition, 17.38% energy from the loaded RF power is converted into dominant fundamental horizontal shear mode (SH0) in the narrow LN mechanical waveguide. Based on this fraction, as a result, 3.51% power relative to the loaded RF energy is scattered into the fundamental longitudinal mode (L0) facing the TFLN-ChG heterogeneous waveguide. The acoustic breathing mode of the heterogeneous OMC is successfully excited under the driving of the propagating L0 mode in the heterogeneous waveguide, demonstrating the great potentials of the heterogeneous piezo-optomechanical transducer in high-performance photon–phonon interaction fields.
2023, 11(9): 1509
随着国家电网规模的不断扩大，架空导线作为电力系统的重要组成，对它的定期巡检变得极其重要，同时，随着低空飞行领域的开放，为了保证国家电网的正常运行及低空飞行的安全，架空导线的识别也变得极其重要。文中提出了一种使用Deeplabv3+语义分割网络模型对红外航拍图像架空导线进行识别的方法，并且针对红外架空导线图像目标的特征对该算法进行了改进。首先在原Deeplabv3+算法的特征提取主干网络ResNet50中加入注意力机制，使网络突出导线目标所在区域的特征，更加关注导线目标所在的位置，进而弱化背景等非主要区域的特征。然后对Deeplabv3+的编码器部分进行改进，在ResNet50模型中加入特征金字塔网络，可以将浅层和深层的特征进行融合，增强网络对不同大小目标属性的识别能力，及导线这种小目标的检测能力，进而提高网络的整体识别效果。实验结果表明：改进后的算法检测性能良好，均像素精度为93.52%，平均交并比为87.83%。Deeplabv3+ 特征金字塔 架空导线 注意力机制 ResNet50 Deeplabv3+ feature pyramid overhead wire attention mechanism ResNet50
2022, 51(11): 20220112
2022, 42(23): 2313001
Scattering-induced glares hinder the detection of weak objects in various scenarios. Recent advances in wavefront shaping show one can not only enhance intensities through constructive interference but also suppress glares within a targeted region via destructive interference. However, due to the lack of a physical model and mathematical guidance, existing approaches have generally adopted a feedback-based scheme, which requires time-consuming hardware iteration. Moreover, glare suppression with up to tens of speckles was demonstrated by controlling thousands of independent elements. Here, we reported the development of a method named two-stage matrix-assisted glare suppression (TAGS), which is capable of suppressing glares at a large scale without triggering time-consuming hardware iteration. By using the TAGS, we experimentally darkened an area containing 100 speckles by controlling only 100 independent elements, achieving an average intensity of only 0.11 of the original value. It is also noticeable that the TAGS is computationally efficient, which only takes 0.35 s to retrieve the matrix and 0.11 s to synthesize the wavefront. With the same number of independent controls, further demonstrations on suppressing larger scales up to 256 speckles were also reported. We envision that the superior performance of the TAGS at a large scale can be beneficial to a variety of demanding imaging tasks under a scattering environment.
2022, 10(12): 2693
针对跨海光通信系统，海岸两侧供电架构导致的能效问题是限制其容量的主要因素。多根单模光纤（M-SMF）复用是目前阶段提高通信海缆容量的主要解决方案。然而，海缆中可容纳的光纤数量往往受限于其机械特性和下缆难度，可容纳光纤数量目前通常限制在32以下。因此，高复用密度的空分复用技术有望在海缆通信领域中展现其优势。对基于多芯光纤（MCF）海缆的能效公式进行了理论推导，对比了MCF海缆与M-SMF海缆的能效特性，并分析多芯耦合器插损、芯间串扰等边际参数对系统总体能效的影响。结果证明：采用4芯光纤在跨大西洋海缆和跨太平洋海缆中的最优光纤数目分别为86和14；采用7芯光纤在跨大西洋海缆和跨太平洋海缆中的最优光纤数目分别为50和8。在海缆最大容纳光纤数目（32）情况下：4芯光纤在跨大西洋场景和跨太平洋场景中相比M-SMF海缆可以提升能效至2.50倍和1.13倍；7芯光纤在跨大西洋场景和跨太平洋场景中相比M-SMF海缆可以提升能效至3.20倍和1.13倍。光通信 光纤特征 光纤表征 光复用 optical communications fiber properties fiber characterization optical multiplexing
2022, 42(15): 1506005
We demonstrate a portable system integrated with time comparison, absolute distance ranging, and optical communication (TRC) to meet the requirements of space gravitational wave detection. A 1 km free-space asynchronous two-way optical link is performed. The TRC realizes optical communication with bit error rate with a Si avalanche photodiode single-photon detector, while the signal intensity is 1.4 photons per pulse with the background noise of counts per second. The distance measurement uncertainty is 48.3 mm, and time comparison precision is 162.4 ps. In this TRC system, a vertical-cavity surface-emitting laser diode with a power of 9.1 µW is used, and the equivalent receiving aperture is 0.5 mm. The TRC provides a miniaturization solution for ultra-long distance inter-satellite communication, time comparison, and ranging for space gravitational wave detectors.gravitational waves detection time comparison optical communication ranging
Chinese Optics Letters
2022, 20(10): 100601
2022, 51(5): 20220312
Mode-division multiplexing (MDM) can greatly improve the capacity of information transmission. The multimode waveguide bend (MWB) with small size and high performance is of great significance for the on-chip MDM integrated system. In this paper, an MWB with high performance based on double free-form curves (DFFCs) is proposed and realized. The DFFC is a combination of a series of arcs optimized by the inverse design method. The fabrication of this MWB only needs one-step lithography and plasma etching and has a large fabrication tolerance. MWBs with effective radii of 6 μm and 10 μm are designed to support three modes and four modes, respectively. The proposed method gives the best overall performance considering both the effective bending radius and the transmission efficiency. The fabricated MWB with four mode channels has low excess losses and crosstalks below in the wavelength range from 1520 to 1580 nm. It is expected that this design can play an important role in promoting the dense integration of multimode transmission systems.
2022, 10(6): 06001484
2022, 59(2): 0204001
We demonstrate a multi-channel pseudo-random coding single-photon ranging system. A pseudo-random multiplexing technique is proposed, which realizes multi-channel pseudo-random ranging only by using one single-photon detector and processing circuit. Compared with the time division multiplexing technique, it will not reduce the maximum unambiguous range while increasing the number of the ranging channel. Eight-channel pseudo-random coding single-photon ranging was realized with the ranging accuracy better than 2 cm. Moreover, photon counting imaging was realized through scanning the laser beams of the eight-channel pseudo-random ranging system. There is no crosstalk between channels, which is suitable for multi-beam long-distance single-photon Lidar.single-photon detection pseudo-random modulation laser ranging
Chinese Optics Letters
2022, 20(2): 021202