Mar 2022, Volume 15 Issue 1

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  • Silicon photonics is to study the use of CMOS process compatible silicon-based platform to realize the scale integration of photonic devices, electronic devices and optoelectronic devices. The applications of silicon photonics cover a wide range of fields, such as data center optical interconnection, optical computing, lidar, biochemical sensing, quantum communication and quantum computing.
    This special issue (Recent Advances in Silicon Photonics (Guest Editors: Dingsha [Detail] ...

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    Ciyuan Qiu, Huifu Xiao, Liheng Wang, Yonghui Tian

    Optical directed logic (DL) is a novel logic operation scheme that employs electrical signals as operands to control the working states of optical switches to perform the logic functions. This review first provides an overview of the concept and working principle of DL. The developing trends of DL computing are then discussed in detail, including the fundamental optical DL gates, combinational optical DL operations, reconfigurable logic computing, low power optical logic computing, and programmable photonic network. The concluding remarks provide an outlook on the DL future development and its impacts in optical computing.

    Haozhe Zhang, Zhe Wang, Zhixun Wang, Bing He, Mengxiao Chen, Miao Qi, Yanting Liu, Jiwu Xin, Lei Wei

    Wearable electronics on fibers or fabrics assembled with electronic functions provide a platform for sensors, displays, circuitry, and computation. These new conceptual devices are human-friendly and programmable, which makes them indispensable for modern electronics. Their unique properties such as being adaptable in daily life, as well as being lightweight and flexible, have enabled many promising applications in robotics, healthcare, and the Internet of Things (IoT). Transistors, one of the fundamental blocks in electronic systems, allow for signal processing and computing. Therefore, study leading to integration of transistors with fabrics has become intensive. Here, several aspects of fiber-based transistors are addressed, including materials, system structures, and their functional devices such as sensory, logical circuitry, memory devices as well as neuromorphic computation. Recently reported advances in development and challenges to realizing fully integrated electronic textile (e-textile) systems are also discussed.

    Jinmin Ding, Fanchao Meng, Xiaoting Zhao, Xin Wang, Shuqin Lou, Xinzhi Sheng, Luyun Yang, Guangming Tao, Sheng Liang

    In this paper, a novel all-solid anti-resonant single crystal fiber (AR-SCF) with high refractive index tubes cladding is proposed. By producing the cladding tubes with high refractive index material, the AR guiding mechanism can be realized for the SCF, which can reduce the mode number to achieve single-mode or few-mode transmission. The influences of different materials and structures on the confinement loss and effective guided mode number for wavelengths of 2–3 μm are investigated. Then, the optimal AR-SCF structures for different wavelengths are determined. Furthermore, the influences of different fabrication errors are analyzed. This work would provide insight to new opportunities in the novel design of SCFs by AR, which would greatly impact the fields of laser application, supercontinum generation, and SCF sensors.

    Clément Strutynski, Vincent Couderc, Tigran Mansuryan, Giorgio Santarelli, Philippe Thomas, Sylvain Danto, Thierry Cardinal

    Here we present the ability of Nd3+-doped zinc-phosphate glasses to be shaped into rectangular core fibers. At first, the physico-chemical properties of the developed P2O5-based materials are investigated for different concentrations of neodymium oxide and core and cladding glass compositions are selected for further fiber development. A modified stack-and-draw technique is used to produce multimode large rectangular-core optical fibers. Self-guided nonlinear effects acting as spatial beam reshaping processes occurring in these newly-developed photonic structures lead to the generation of spectral broadenings in the visible and near-infrared spectral domains.

    Zihan Tao, Bo Wang, Bowen Bai, Ruixuan Chen, Haowen Shu, Xuguang Zhang, Xingjun Wang

    Integrated waveguides with slot structures have attracted increasing attention due to their advantages of tight mode confinement and strong light-matter interaction. Although extensively studied, the issue of mode mismatch with other strip waveguide-based optical devices is a huge challenge that prevents integrated waveguides from being widely utilized in large-scale photonic-based circuits. In this paper, we demonstrate an ultra-compact low-loss slot-strip converter with polarization insensitivity based on the multimode interference (MMI) effect. Sleek sinusoidal profiles are adopted to allow for smooth connection between the slot and strip waveguide, resulting reflection reduction. By manipulating the MMI effect with structure optimization, the self-imaging positions of the TE0 and TM0 modes are aligned with minimized footprint, leading to low-loss transmission for both polarizations. The measurement results show that high coupling efficiencies of − 0.40 and − 0.64 dB are achieved for TE0 and TM0 polarizations, respectively. The device has dimensions as small as 1.1 μm × 1.2 μm and composed of factory-available structures. The above characteristics of our proposed compact slot-strip converter makes it a promising device for future deployment in multi-functional integrated photonics systems.

    Seyedeh Leila Mortazavifar, Mohammad Reza Salehi, Mojtaba Shahraki, Ebrahim Abiri

    This paper investigates how the dimensions and arrangements of stadium silicon nanowires (NWs) affect their absorption properties. Compared to other NWs, the structure proposed here has a simple geometry, while its absorption rate is comparable to that of very complex structures. It is shown that changing the cross-section of NW from circular (or rectangular) to a stadium shape leads to change in the position and the number of absorption modes of the NW. In a special case, these modes result in the maximum absorption inside NWs. Another method used in this paper to attain broadband absorption is utilization of multiple NWs which have different geometries. However, the maximum enhancement is achieved using non-close packed NW. These structures can support more cavity modes, while NW scattering leads to broadening of the absorption spectra. All the structures are optimized using particle swarm optimizations. Using these optimized structures, it is viable to enhance the absorption by solar cells without introducing more absorbent materials.

    Jeremy C. Adcock, Yunhong Ding

    Photonics is poised to play a unique role in quantum technology for computation, communications and sensing. Meanwhile, integrated photonic circuits—with their intrinsic phase stability and high-performance, nanoscale components—offer a route to scaling. However, each integrated platform has a unique set of advantages and pitfalls, which can limit their power. So far, the most advanced demonstrations of quantum photonic circuitry has been in silicon photonics. However, thin-film lithium niobate (TFLN) is emerging as a powerful platform with unique capabilities; advances in fabrication have yielded loss metrics competitive with any integrated photonics platform, while its large second-order nonlinearity provides efficient nonlinear processing and ultra-fast modulation. In this short review, we explore the prospects of dynamic quantum circuits—such as multiplexed photon sources and entanglement generation—on hybrid TFLN on silicon (TFLN/Si) photonics and argue that hybrid TFLN/Si photonics may have the capability to deliver the photonic quantum technology of tomorrow.

    Han Gao, Miao Yang, Xing Liu, Xianglong Dai, Xiao-Qing Bao, Dehua Xiong

    Hydrogen production from water splitting provides an effective method to alleviate the ever-growing global energy crisis. In this work, delafossite CuGaO2 (CGO) crystal was synthesized through hydrothermal routes with Cu(NO3)2·3H2O and Ga(NO3)3·xH2O used as reactants. The addition of cetyltrimethylammonium bromide (CTAB) was found to play an important role in modifying the morphology of CuGaO2 (CGO-CTAB). With the addition of CTAB, the morphology of CGO-CTAB samples changed from irregular flake to typical hexagonal sheet microstructure, with an average size of 1–2 µm and a thickness of around 100 nm. Furthermore, the electrocatalytic activity of CGO-CTAB crystals for oxygen evolution reaction (OER) was also studied and compared with that of CGO crystals. CGO-CTAB samples exhibited better activity than CGO. An overpotential of 391.5 mV was shown to be able to generate a current density of 10 mA/cm2. The as-prepared samples also demonstrate good stability for water oxidation and relatively fast OER kinetics with a Tafel slope of 56.4 mV/dec. This work highlights the significant role of modification of CTAB surfactants in preparing CGO related crystals, and the introduction of CTAB was found to help to improve their electrocatalytic activity for OER.

    Shengping Liu, Junbo Feng, Ye Tian, Heng Zhao, Li Jin, Boling Ouyang, Jiguang Zhu, Jin Guo

    Silicon photonic platforms offer relevance to large markets in many applications, such as optical phased arrays, photonic neural networks, programmable photonic integrated circuits, and quantum computation devices. As one of the basic tuning devices, the thermo-optic phase shifter (TOPS) plays an important role in all these applications. A TOPS with the merits of easy fabrication, low power consumption, small thermal time constant, low insertion loss, small footprint, and low crosstalk, is needed to improve the performance and lower the cost of the above applications. To meet these demands, various TOPS have been proposed and experimentally demonstrated on different foundry platforms In this paper, we review the state-of-the-art of TOPS, including metal heater, doped silicon, silicide, with silicon substrate undercut for heat insulation, folded waveguide structure, and multi-pass waveguide structure. We further compare these TOPSs and propose the directions of the future developments on TOPS.

    Shihao Xu, Xiaowei Liu, Zehua Yu, Kang Liu

    Negative pressure in water under tension, as a thermodynamic non-equilibrium state, has facilitated the emergence of innovative technologies on microfluidics, desalination, and thermal management. However, the lack of a simple and accurate method to measure negative pressure hinders further in-depth understanding of the properties of water in such a state. In this work, we propose a non-contact optical method to quantify the negative pressure in micron-sized water voids of a hydrogel film based on the microscale mechanical deformation of the hydrogel itself. We tested three groups of hydrogel samples with different negative pressure inside, and the obtained results fit well with the theoretical prediction. Furthermore, we demonstrated that this method can characterize the distribution of negative pressure, and can thus provide the possibility of investigation of the flow behavior of water in negative pressure. These results prove this technique to be a promising approach to characterization of water under tension and for investigation of its properties under negative pressure.

    Xianfeng Qiao, Shu Xiao, Peisen Yuan, Dezhi Yang, Dongge Ma

    The transient electroluminescence (EL) technique is widely used to evaluate the carrier mobility in the field of organic light emitting diodes. The traditional analog detection strategy using oscilloscopes is generally limited since the background noise causes an underestimation of the mobility value. In this paper, we utilize time-correlated single-photon counting (TCSPC) to probe the transient EL for mobility calculation. The measurements on tris(8-hydroxyquinoline) aluminum (Alq3) show that the electron mobilities obtained using the TCSPC technique are slightly higher than those obtained from the analog method at all the investigated voltages. Moreover, the TCSPC mobilities demonstrate weaker dependence on the root of electrical field compared to the oscilloscope mobilities. These improvements are attributed to the unique principle of TCSPC, which quantifies the EL intensity by counting the number of single-photon pulses, improving its single-photon sensitivity and eliminating the negative impacts of electrical noise. These advantages make TCSPC a powerful technique in the characterization of time-resolved electroluminescence.

    Peiyan Li, Shaojie Liu, Xinhou Chen, Chunyan Geng, Xiaojun Wu

    Highly efficient generation and arbitrary manipulation of spin-polarized terahertz (THz) radiation will enable chiral lightwave driven quantum nonequilibrium state regulation, induce new electronic structures, consequently provide a powerful experimental tool for investigation of nonlinear THz optics and extreme THz science and applications. THz circular dichromic spectroscopy, ultrafast electron bunch manipulation, as well as THz imaging, sensing, and telecommunication, also need chiral THz waves. Here we review optical generation of circularly-polarized THz radiation but focus on recently emerged polarization tunable spintronic THz emission techniques, which possess many advantages of ultra-broadband, high efficiency, low cost, easy for integration and so on. We believe that chiral THz sources based on the combination of electron spin, ultrafast optical techniques and material structure engineering will accelerate the development of THz science and applications.

    Galina Georgieva, Christian Mai, Pascal M. Seiler, Anna Peczek, Lars Zimmermann

    In this paper, we report on polarization combining two-dimensional grating couplers (2D GCs) on amorphous Si:H, fabricated in the backend of line of a photonic BiCMOS platform. The 2D GCs can be used as an interface of a hybrid silicon photonic coherent transmitter, which can be implemented on bulk Si wafers. The fabricated 2D GCs operate in the telecom C-band and show an experimental coupling efficiency of − 5 dB with a wafer variation of ± 1.2 dB. Possibilities for efficiency enhancement and improved performance stability in future design generations are outlined and extension toward O-band devices is also investigated.

    Jianxing Pan, Chaoyu Xu, Zhichao Wu, Jing Zhang, Tianye Huang, Perry Ping Shum

    Recent researches have demonstrated that pulsed driving is an effective method to increase the temporal overlap between cavity soliton (CS) and pump field, thereby increasing the pump-to-comb conversion efficiency. The amplitude-modulated inhomogeneity of the background wave causes the solitons to drift toward edges of the driving pulse. To eliminate the multiple temporal trapping positions, induced by the spontaneous symmetry breaking, we propose the chirped pulse driving for deterministic single soliton generation. We theoretically explain the physical mechanism of the chirp pulse driving, as the combination of amplitude and phase modulation. Our numerical simulations demonstrate the chirp is responsible for the single soliton generation. A detailed investigation for dynamics of CSs sustained by chirped pulses, shows the recovery of spontaneous symmetry breaking. In addition, the desynchronized chirped pulse driving is also considered here. Considering a weak chirp parameter, the desynchronization-dependent trapping position diagram is divided into multiple areas including two CSs, a single CS, two oscillating CSs, and no CS. With a sufficient chirp parameter considered, the trapping position curve becomes a monotonous function of the desynchronized drift velocity, which indicates deterministic single soliton generation.