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  • RESEARCH ARTICLE
    Novel elastomeric spiropyran-doped poly(dimethylsiloxane) optical waveguide for UV sensing
    Camila Aparecida Zimmermann, Koffi Novignon Amouzou, Dipankar Sengupta, Aashutosh Kumar, Nicole Raymonde Demarquette, Bora Ung
    Frontiers of Optoelectronics, 2024, 17(3): 21. https://doi.org/10.1007/s12200-024-00124-4

    Novel poly(dimethylsiloxane) (PDMS) doped with two different spiropyran derivatives (SP) were investigated as potential candidates for the preparation of elastomeric waveguides with UV-dependent optical properties. First, free-standing films were prepared and evaluated with respect to their photochromic response to UV irradiation. Kinetics, reversibility as well as photofatigue and refractive index of the SP-doped PDMS samples were assessed. Second, SP-doped PDMS waveguides were fabricated and tested as UV sensors by monitoring changes in the transmitted optical power of a visible laser (633 nm). UV sensing was successfully demonstrated by doping PDMS using one spiropyran derivative whose propagation loss was measured as 1.04 dB/cm at 633 nm, and sensitivity estimated at 115% change in transmitted optical power per unit change in UV dose. The decay and recovery time constants were measured at 42 and 107 s, respectively, with an average UV saturation dose of 0.4 J/cm2. The prepared waveguides exhibited a reversible and consistent response even under bending. The sensor parameters can be tailored by varying the waveguide length up to 21 cm, and are affected by white light and temperatures up to 70 ℃. This work is relevant to elastomeric optics, smart optical materials, and polymer optical waveguide sensors.

  • REVIEW ARTICLE
    Information processing at the speed of light
    Muhammad AbuGhanem
    Frontiers of Optoelectronics, 2024, 17(4): 33. https://doi.org/10.1007/s12200-024-00133-3

    In recent years, quantum computing has made significant strides, particularly in light-based technology. The introduction of quantum photonic chips has ushered in an era marked by scalability, stability, and cost-effectiveness, paving the way for innovative possibilities within compact footprints. This article provides a comprehensive exploration of photonic quantum computing, covering key aspects such as encoding information in photons, the merits of photonic qubits, and essential photonic device components including light squeezers, quantum light sources, interferometers, photodetectors, and wave-guides. The article also examines photonic quantum communication and internet, and its implications for secure systems, detailing implementations such as quantum key distribution and long-distance communication. Emerging trends in quantum communication and essential reconfigurable elements for advancing photonic quantum internet are discussed. The review further navigates the path towards establishing scalable and fault-tolerant photonic quantum computers, highlighting quantum computational advantages achieved using photons. Additionally, the discussion extends to programmable photonic circuits, integrated photonics and transformative applications. Lastly, the review addresses prospects, implications, and challenges in photonic quantum computing, offering valuable insights into current advancements and promising future directions in this technology.

  • RESEARCH ARTICLE
    Pulsed THz radiation under ultrafast optical discharge of vacuum photodiode
    Aleksandr Ushakov, Kseniia Mamaeva, Leonid Seleznev, Georgy Rizaev, Vladimir Bukin, Timophey Dolmatov, Pavel Chizhov, Vladimir Bagdasarov, Sergey Garnov
    Frontiers of Optoelectronics, 2024, 17(2): 20. https://doi.org/10.1007/s12200-024-00123-5

    In this paper, we first present an experimental demonstration of terahertz radiation pulse generation with energy up to 5 pJ under the electron emission during ultrafast optical discharge of a vacuum photodiode. We use a femtosecond optical excitation of metallic copper photocathode for the generation of ultrashort electron bunch and up to 45 kV/cm external electric field for the photo-emitted electron acceleration. Measurements of terahertz pulses energy as a function of emitted charge density, incidence angle of optical radiation and applied electric field have been provided. Spectral and polarization characteristics of generated terahertz pulses have also been studied. The proposed semi-analytical model and simulations in COMSOL Multiphysics prove the experimental data and allow for the optimization of experimental conditions aimed at flexible control of radiation parameters.

  • RESEARCH ARTICLE
    Information-entropy enabled identifying topological photonic phase in real space
    Rui Ma, Qiuchen Yan, Yihao Luo, Yandong Li, Xingyuan Wang, Cuicui Lu, Xiaoyong Hu, Qihuang Gong
    Frontiers of Optoelectronics, 2024, 17(2): 11. https://doi.org/10.1007/s12200-024-00113-7

    The topological photonics plays an important role in the fields of fundamental physics and photonic devices. The traditional method of designing topological system is based on the momentum space, which is not a direct and convenient way to grasp the topological properties, especially for the perturbative structures or coupled systems. Here, we propose an interdisciplinary approach to study the topological systems in real space through combining the information entropy and topological photonics. As a proof of concept, the Kagome model has been analyzed with information entropy. We reveal that the bandgap closing does not correspond to the topological edge state disappearing. This method can be used to identify the topological phase conveniently and directly, even the systems with perturbations or couplings. As a promotional validation, Su–Schrieffer–Heeger model and the valley-Hall photonic crystal have also been studied based on the information entropy method. This work provides a method to study topological photonic phase based on information theory, and brings inspiration to analyze the physical properties by taking advantage of interdisciplinarity.

  • REVIEW ARTICLE
    Contactless integrated photonic probes: fundamentals, characteristics, and applications
    Guangze Wu, Yuanjian Wan, Zhao Wang, Xiaolong Hu, Jinwei Zeng, Yu Zhang, Jian Wang
    Frontiers of Optoelectronics, 2024, 17(3): 26. https://doi.org/10.1007/s12200-024-00127-1

    On-chip optical power monitors are indispensable for functional implementation and stabilization of large-scale and complex photonic integrated circuits (PICs). Traditional on-chip optical monitoring is implemented by tapping a small portion of optical power from the waveguide, which leads to significant loss. Due to its advantages like non-invasive nature, miniaturization, and complementary metal-oxide-semiconductor (CMOS) process compatibility, a transparent monitor named the contactless integrated photonic probe (CLIPP), has been attracting great attention in recent years. The CLIPP indirectly monitors the optical power in the waveguide by detecting the conductance variation of the local optical waveguide caused by the surface state absorption (SSA) effect. In this review, we first introduce the fundamentals of the CLIPP including the concept, the equivalent electric model and the impedance read-out method, and then summarize some characteristics of the CLIPP. Finally, the functional applications of the CLIPP on the identification and feedback control of optical signal are discussed, followed by a brief outlook on the prospects of the CLIPP.

  • RESEARCH ARTICLE
    Harnessing sub-comb dynamics in a graphene-sensitized microresonator for gas detection
    Yupei Liang, Mingyu Liu, Fan Tang, Yanhong Guo, Hao Zhang, Shihan Liu, Yanping Yang, Guangming Zhao, Teng Tan, Baicheng Yao
    Frontiers of Optoelectronics, 2024, 17(2): 12. https://doi.org/10.1007/s12200-024-00115-5

    Since their inception, frequency combs generated in microresonators, known as microcombs, have sparked significant scientific interests. Among the various applications leveraging microcombs, soliton microcombs are often preferred due to their inherent mode-locking capability. However, this choice introduces additional system complexity because an initialization process is required. Meanwhile, despite the theoretical understanding of the dynamics of other comb states, their practical potential, particularly in applications like sensing where simplicity is valued, remains largely untapped. Here, we demonstrate controllable generation of sub-combs that bypasses the need for accessing bistable regime. And in a graphene-sensitized microresonator, the sub-comb heterodynes produce stable, accurate microwave signals for high-precision gas detection. By exploring the formation dynamics of sub-combs, we achieved 2 MHz harmonic comb-to-comb beat notes with a signal-to-noise ratio (SNR) greater than 50 dB and phase noise as low as – 82 dBc/Hz at 1 MHz offset. The graphene sensitization on the intracavity probes results in exceptional frequency responsiveness to the adsorption of gas molecules on the graphene of microcavity surface, enabling detect limits down to the parts per billion (ppb) level. This synergy between graphene and sub-comb formation dynamics in a microcavity structure showcases the feasibility of utilizing microcombs in an incoherent state prior to soliton locking. It may mark a significant step toward the development of easy-to-operate, systemically simple, compact, and high-performance photonic sensors.

  • RESEARCH ARTICLE
    Dual-functional application of Ca2Ta2O7: Bi3+/Eu3+ phosphors in multicolor tunable optical thermometry and WLED
    Jingjing Ru, Bing Zhao, Fan Zeng, Feiyun Guo, Jinhua Liu, Jianzhong Chen
    Frontiers of Optoelectronics, 2024, 17(3): 31. https://doi.org/10.1007/s12200-024-00134-2

    A series of Bi3+/Eu3+ co-doped Ca2Ta2O7 (CTO:Bi3+/Eu3+) phosphors were prepared by high-temperature solid-state method for dual-emission center optical thermometers and white light-emitting diode (WLED) device. By modulating the doping ratio of Bi3+/Eu3+ and utilizing the energy transfer from Bi3+ to Eu3+, the tunable color emission ranging from green to reddish-orange was realized. The designed CTO:0.04Bi3+/Eu3+ optical thermometers exhibit significant thermochromism, superior stability, and repeatability, with maximum sensitivities of Sa = 0.055 K-1 (at 510 K) and Sr = 1.298% K-1 (at 480 K) within the temperature range of 300–510 K, owing to the different thermal quenching behaviors between Bi3+ and Eu3+ ions. These features indicate the potential application prospects of the prepared samples in visualized thermometer or high-temperature safety marking. Furthermore, leveraging the excellent zero-thermal-quenching performance, outstanding acid/alkali resistance, and color stability of CTO:0.04Bi3+/0.16Eu3+ phosphor, a WLED device with a high Ra value of 95.3 has been realized through its combination with commercially available blue and green phosphors, thereby demonstrating the potential application of CTO:0.04Bi3+/0.16Eu3+ in near-UV pumped WLED devices.

  • RESEARCH ARTICLE
    Coherent beam combining of two all-PM thulium-doped fiber chirped pulse amplifiers
    Bo Ren, Hongxiang Chang, Can Li, Tao Wang, Kaikai Jin, Jiayi Zhang, Kun Guo, Rongtao Su, Jinyong Leng, Pu Zhou
    Frontiers of Optoelectronics, 2024, 17(2): 14. https://doi.org/10.1007/s12200-024-00117-3

    In this paper, we report a coherent beam combining (CBC) system that involves two thulium-doped all-polarization maintaining (PM) fiber chirped pulse amplifiers. Through phase-locking the two channels via a fiber stretcher by using the stochastic parallel gradient descent (SPGD) algorithm, a maximum average power of 265 W is obtained, with a CBC efficiency of 81% and a residual phase error of λ/17. After de-chirping by a pair of diffraction gratings, the duration of the combined laser pulse is compressed to 690 fs. Taking into account the compression efficiency of 90% and the main peak energy proportion of 91%, the corresponding peak power is calculated to be 4 MW. The laser noise characteristics before and after CBC are examined, and the results indicate that the CBC would degrade the low frequency relative intensity noise (RIN), of which the integration is 1.74% in [100 Hz, 2 MHz] at the maximum combined output power. In addition, the effects of the nonlinear spectrum broadening during chirped pulse amplification on the CBC efficiency are also investigated, showing that a higher extent of pulse stretching is effective in alleviating the spectrum broadening and realizing a higher output power with decent combining efficiency.

  • RESEARCH ARTICLE
    MEMS-actuated terahertz metamaterials driven by phase-transition materials
    Zhixiang Huang, Weipeng Wu, Eric Herrmann, Ke Ma, Zizwe A. Chase, Thomas A. Searles, M. Benjamin Jungfleisch, Xi Wang
    Frontiers of Optoelectronics, 2024, 17(2): 13. https://doi.org/10.1007/s12200-024-00116-4

    The non-ionizing and penetrative characteristics of terahertz (THz) radiation have recently led to its adoption across a variety of applications. To effectively utilize THz radiation, modulators with precise control are imperative. While most recent THz modulators manipulate the amplitude, frequency, or phase of incident THz radiation, considerably less progress has been made toward THz polarization modulation. Conventional methods for polarization control suffer from high driving voltages, restricted modulation depth, and narrow band capabilities, which hinder device performance and broader applications. Consequently, an ideal THz modulator that offers high modulation depth along with ease of processing and operation is required. In this paper, we propose and realize a THz metamaterial comprised of microelectromechanical systems (MEMS) actuated by the phase-transition material vanadium dioxide (VO2). Simulation and experimental results of the three-dimensional metamaterials show that by leveraging the unique phase-transition attributes of VO2, our THz polarization modulator offers notable advancements over existing designs, including broad operation spectrum, high modulation depth, ease of fabrication, ease of operation condition, and continuous modulation capabilities. These enhanced features make the system a viable candidate for a range of THz applications, including telecommunications, imaging, and radar systems.

  • COMMUNICATION
    Circularly polarized light emission and detection by chiral inorganic semiconductors
    Zha Li, Wancai Li, Dehui Li, Wei Tang, Huageng Liang, Huaibing Song, Chao Chen, Liang Gao, Jiang Tang
    Frontiers of Optoelectronics, 2024, 17(2): 15. https://doi.org/10.1007/s12200-024-00120-8

    Chiral inorganic semiconductors with high dissymmetric factor are highly desirable, but it is generally difficult to induce chiral structure in inorganic semiconductors because of their structure rigidity and symmetry. In this study, we introduced chiral ZnO film as hard template to transfer chirality to CsPbBr3 film and PbS quantum dots (QDs) for circularly polarized light (CPL) emission and detection, respectively. The prepared CsPbBr3/ZnO thin film exhibited CPL emission at 520 nm and the PbS QDs/ZnO film realized CPL detection at 780 nm, featuring high dissymmetric factor up to around 0.4. The electron transition based mechanism is responsible for chirality transfer.

  • RESEARCH ARTICLE
    Low-light enhancement method with dual branch feature fusion and learnable regularized attention
    Yixiang Sun, Mengyao Ni, Ming Zhao, Zhenyu Yang, Yuanlong Peng, Danhua Cao
    Frontiers of Optoelectronics, 2024, 17(3): 28. https://doi.org/10.1007/s12200-024-00129-z

    Restricted by the lighting conditions, the images captured at night tend to suffer from color aberration, noise, and other unfavorable factors, making it difficult for subsequent vision-based applications. To solve this problem, we propose a two-stage size-controllable low-light enhancement method, named Dual Fusion Enhancement Net (DFEN). The whole algorithm is built on a double U-Net structure, implementing brightness adjustment and detail revision respectively. A dual branch feature fusion module is adopted to enhance its ability of feature extraction and aggregation. We also design a learnable regularized attention module to balance the enhancement effect on different regions. Besides, we introduce a cosine training strategy to smooth the transition of the training target from the brightness adjustment stage to the detail revision stage during the training process. The proposed DFEN is tested on several low-light datasets, and the experimental results demonstrate that the algorithm achieves superior enhancement results with the similar parameters. It is worth noting that the lightest DFEN model reaches 11 FPS for image size of 1224×1024 in an RTX 3090 GPU.

  • RESEARCH ARTICLE
    Monolayer graphene/GaN heterostructure photodetector with UV-IR dual-wavelength photoresponses
    Junjun Xue, Jiaming Tong, Zhujun Gao, Zhouyu Chen, Haoyu Fang, Saisai Wang, Ting Zhi, Jin Wang
    Frontiers of Optoelectronics, 2024, 17(2): 17. https://doi.org/10.1007/s12200-024-00121-7

    An ultraviolet-infrared (UV-IR) dual-wavelength photodetector (PD) based on a monolayer (ML) graphene/GaN heterostructure has been successfully fabricated in this work. The ML graphene was synthesized by chemical vapor deposition (CVD) and subsequently transferred onto GaN substrate using polymethylmethacrylate (PMMA). The morphological and optical properties of the as-prepared graphene and GaN were presented. The fabricated PD based on the graphene/GaN heterostructure exhibited excellent rectify behavior by measuring the current–voltage (I–V) characteristics under dark conditions, and the spectral response demonstrated that the device revealed an UV-IR dual-wavelength photoresponse. In addition, the energy band structure and absorption properties of the ML graphene/GaN heterostructure were theoretically investigated based on density functional theory (DFT) to explore the underlying physical mechanism of the two-dimensional (2D)/three-dimensional (3D) hybrid heterostructure PD device. This work paves the way for the development of innovative GaN-based dual-wavelength optoelectronic devices, offering a potential strategy for future applications in the field of advanced photodetection technology.

  • RESEARCH ARTICLE
    Polarization and wavelength routers based on diffractive neural network
    Xiaohong Lin, Yulan Fu, Kuo Zhang, Xinping Zhang, Shuai Feng, Xiaoyong Hu
    Frontiers of Optoelectronics, 2024, 17(3): 22. https://doi.org/10.1007/s12200-024-00126-2

    In the field of information processing, all-optical routers are significant for achieving high-speed, high-capacity signal processing and transmission. In this study, we developed three types of structurally simple and flexible routers using the deep diffractive neural network (D2NN), capable of routing incident light based on wavelength and polarization. First, we implemented a polarization router for routing two orthogonally polarized light beams. The second type is the wavelength router that can route light with wavelengths of 1550, 1300, and 1100 nm, demonstrating outstanding performance with insertion loss as low as 0.013 dB and an extinction ratio of up to 18.96 dB, while also maintaining excellent polarization preservation. The final router is the polarization-wavelength composite router, capable of routing six types of input light formed by pairwise combinations of three wavelengths (1550, 1300, and 1100 nm) and two orthogonal linearly polarized lights, thereby enhancing the information processing capability of the device. These devices feature compact structures, maintaining high contrast while exhibiting low loss and passive characteristics, making them suitable for integration into future optical components. This study introduces new avenues and methodologies to enhance performance and broaden the applications of future optical information processing systems.

  • RESEARCH ARTICLE
    Mode division multiplexing reconstructive spectrometer with an all-fiber photonics lantern
    Junrui Liang, Jun Ye, Xiaoya Ma, Yao Lu, Jun Li, Jiangming Xu, Zilun Chen, Jinyong Leng, Zongfu Jiang, Pu Zhou
    Frontiers of Optoelectronics, 2024, 17(3): 23. https://doi.org/10.1007/s12200-024-00130-6

    This study presents a high-accuracy, all-fiber mode division multiplexing (MDM) reconstructive spectrometer (RS). The MDM was achieved by utilizing a custom-designed 3 × 1 mode-selective photonics lantern to launch distinct spatial modes into the multimode fiber (MMF). This facilitated the information transmission by increasing light scattering processes, thereby encoding the optical spectra more comprehensively into speckle patterns. Spectral resolution of 2 pm and the recovery of 2000 spectral channels were accomplished. Compared to methods employing single-mode excitation and two-mode excitation, the three-mode excitation method reduced the recovered error by 88% and 50% respectively. A resolution enhancement approach based on alternating mode modulation was proposed, reaching the MMF limit for the 3 dB bandwidth of the spectral correlation function. The proof-of-concept study can be further extended to encompass diverse programmable mode excitations. It is not only succinct and highly efficient but also well-suited for a variety of high-accuracy, high-resolution spectral measurement scenarios.

  • RESEARCH ARTICLE
    Design and simulation investigations on charge transport layers-free in lead-free three absorber layer all-perovskite solar cells
    Guangdong Li, Mingxiang Xu, Zhong Chen
    Frontiers of Optoelectronics, 2024, 17(2): 18. https://doi.org/10.1007/s12200-024-00119-1

    The multiple absorber layer perovskite solar cells (PSCs) with charge transport layers-free (CTLs-free) have drawn widespread research interest due to their simplified architecture and promising photoelectric characteristics. Under the circumstances, the novel design of CTLs-free inversion PSCs with stable and nontoxic three absorber layers (triple Cs3Bi2I9, single MASnI3, double Cs2TiBr6) as optical-harvester has been numerically simulated by utilizing wxAMPS simulation software and achieved high power conversion efficiency (PCE) of 14.8834%. This is owing to the innovative architecture of PSCs favors efficient transport and extraction of more holes and the slender band gap MASnI3 extends the absorption spectrum to the near-infrared periphery compared with the two absorber layers architecture of PSCs. Moreover, the performance of the device with p-type-Cs3Bi2I9/p-type-MASnI3/n-type-Cs2TiBr6 architecture is superior to the one with the p-type-Cs3Bi2I9/n-type-MASnI3/n-type-Cs2TiBr6 architecture due to less carrier recombination and higher carrier life time inside the absorber layers. The simulation results reveal that Cs2TiF6 double perovskite material stands out as the best alternative. Additionally, an excellent PCE of 21.4530% can be obtained with the thicker MASnI3 absorber layer thickness (0.4 µm). Lastly, the highest-performance photovoltaic devices (28.6193%) can be created with the optimized perovskite doping density of around E15 cm3 (Cs3Bi2I9), E18 cm3 (MASnI3), and 1.5E19 cm3 (Cs2TiBr6). This work manifests that the proposed CTLs-free PSCs with multi-absorber layers shall be a relevant reference for forward applications in electro-optical and optoelectronic devices.

  • RESEARCH ARTICLE
    Real-time detection of aging status of methylammonium lead iodide perovskite thin films by using terahertz time-domain spectroscopy
    Jinzhuo Xu, Yinghui Wu, Shuting Fan, Xudong Liu, Zhen Yin, Youpeng Yang, Renheng Wang, Zhengfang Qian, Yiwen Sun
    Frontiers of Optoelectronics, 2024, 17(3): 24. https://doi.org/10.1007/s12200-024-00128-0

    The inadequate stability of organic–inorganic hybrid perovskites remains a significant barrier to their widespread commercial application in optoelectronic devices. Aging phenomena profoundly affect the optoelectronic performance of perovskite-based devices. In addition to enhancing perovskite stability, the real-time detection of aging status, aimed at monitoring the aging progression, holds paramount importance for both fundamental research and the commercialization of organic–inorganic hybrid perovskites. In this study, the aging status of perovskite was real-time investigated by using terahertz time-domain spectroscopy. Our analysis consistently revealed a gradual decline in the intensity of the absorption peak at 0.968 THz with increasing perovskite aging. Furthermore, a systematic discussion was conducted on the variations in intensity and position of the terahertz absorption peaks as the perovskite aged. These findings facilitate the real-time assessment of perovskite aging, providing a promising method to expedite the commercialization of perovskite-based optoelectronic devices.

  • RESEARCH ARTICLE
    Design of an on-chip wavelength conversion device assisted by an erbium-ytterbium co-doped waveguide amplifier
    Chen Zhou, Xiwen He, Mingyue Xiao, Deyue Ma, Weibiao Chen, Zhiping Zhou
    Frontiers of Optoelectronics, 2024, 17(2): 16. https://doi.org/10.1007/s12200-024-00118-2

    In current documented studies, it has been observed that wavelength converters utilizing AlGaAsOI waveguides exhibit suboptimal on-chip wavelength conversion efficiency from the C-band to the 2 µm band, generally falling below –20.0 dB. To address this issue, we present a novel wavelength conversion device assisted by a waveguide amplifier, incorporating both AlGaAs wavelength converter and erbium-ytterbium co-doped waveguide amplifier, thereby achieving a notable conversion efficiency exceeding 0 dB. The noteworthy enhancement in efficiency can be attributed to the specific dispersion design of the AlGaAs wavelength converter, which enables an upsurge in conversion efficiency to –15.54 dB under 100 mW of pump power. Furthermore, the integration of an erbium-ytterbium co-doped waveguide amplifier facilitates a loss compensation of over 15 dB. Avoiding the use of external optical amplifiers, this device enables efficient and high-bandwidth wavelength conversion, showing promising applications in various fields, such as optical communication, sensing, imaging, and beyond.

  • LETTER
    Quantitative modeling of perovskite-based direct X-ray flat panel detectors
    Zihao Song, Gaozhu Wang, Jincong Pang, Zhiping Zheng, Ling Xu, Ying Zhou, Guangda Niu, Jiang Tang
    Frontiers of Optoelectronics, 2024, 17(4): 32. https://doi.org/10.1007/s12200-024-00136-0

    Direct X-ray detectors based on semiconductors have drawn great attention from researchers in the pursuing of higher imaging quality. However, many previous works focused on the optimization of detection performances but seldomly watch them in an overall view and analyze how they will influence the detective quantum efficiency (DQE) value. Here, we propose a numerical model which shows the quantitative relationship between DQE and the properties of X-ray detectors and electric circuits. Our results point out that pursuing high sensitivity only is meaningless. To reduce the medical X-ray dose by 80%, the requirement for X-ray sensitivity is only at a magnitude of 103 µCGy-1·cm-2. To achieve the DQE = 0.7 at X-ray sensitivity air from 1248 to 8171 µCGy-1air·cm-2, the requirements on dark current density ranges from 10 to 100 nA·cm-2 and the fluctuation of current density should fall in 0.21 to 1.37 nA·cm-2.

  • REVIEW ARTICLE
    Effect of terahertz radiation on cells and cellular structures
    A. P. Rytik, V. V. Tuchin
    Frontiers of Optoelectronics, 2025, 18(1): 2. https://doi.org/10.1007/s12200-024-00146-y

    The paper presents the results of modern research on the effects of electromagnetic terahertz radiation in the frequency range 0.5-100 THz at different levels of power density and exposure time on the viability of normal and cancer cells. As an accompanying tool for monitoring the effect of radiation on biological cells and tissues, spectroscopic research methods in the terahertz frequency range are described, and attention is focused on the possibility of using the spectra of interstitial water as a marker of pathological processes. The problem of the safety of terahertz radiation for the human body from the point of view of its effect on the structures and systems of biological cells is also considered.

  • RESEARCH ARTICLE
    Impact of device resistances in the performance of graphene-based terahertz photodetectors
    O. Castelló, Sofía M. López Baptista, K. Watanabe, T. Taniguchi, E. Diez, J. E. Velázquez-Pérez, Y. M. Meziani, J. M. Caridad, J. A. Delgado-Notario
    Frontiers of Optoelectronics, 2024, 17(2): 19. https://doi.org/10.1007/s12200-024-00122-6

    In recent years, graphene field-effect-transistors (GFETs) have demonstrated an outstanding potential for terahertz (THz) photodetection due to their fast response and high-sensitivity. Such features are essential to enable emerging THz applications, including 6G wireless communications, quantum information, bioimaging and security. However, the overall performance of these photodetectors may be utterly compromised by the impact of internal resistances presented in the device, so-called access or parasitic resistances. In this work, we provide a detailed study of the influence of internal device resistances in the photoresponse of high-mobility dual-gate GFET detectors. Such dual-gate architectures allow us to fine tune (decrease) the internal resistance of the device by an order of magnitude and consequently demonstrate an improved responsivity and noise-equivalent-power values of the photodetector, respectively. Our results can be well understood by a series resistance model, as shown by the excellent agreement found between the experimental data and theoretical calculations. These findings are therefore relevant to understand and improve the overall performance of existing high-mobility graphene photodetectors.

  • RESEARCH ARTICLE
    Control of visible-range transmission and reflection haze by varying pattern size, shape and depth in flexible metasurfaces
    Avijit Maity, Vaswati Biswas, R. Vijaya
    Frontiers of Optoelectronics, 2024, 17(3): 25. https://doi.org/10.1007/s12200-024-00125-3

    Cost-effective soft imprint lithography technique is used to prepare flexible thin polymeric surfaces containing a periodic arrangement of nanodimples and nanobumps of sub-micron size. Using a single master mold of self-assembled colloidal crystal, metasurfaces with different depths and heights of patterns with a fixed pitch are possible, which makes the process inexpensive and simple. These metasurfaces are studied for their diffuse and total transmission and reflection spectra in the visible range. The transmission haze and reflection haze are calculated from the measurements. The surface containing nanobumps of lesser pattern height result in higher values of reflection and transmission haze than from surfaces containing nanodimples of much higher depth for the same pitch. The haze is more dependent on the pattern depth or height and less dependent on the pitch of the pattern. Far-field transmission profiles measured in the same wavelength range from the patterned surfaces show that the scattering increases with the increase of the ratio of pattern depth/height to pitch, similar to the haze measurements conducted with a closed integrating sphere. These profiles show that the angular spread of scattered light in transmission is within 10°, explaining the reason for the relatively low transmission haze in all the patterned surfaces. Simulation results confirm that the nanobump pattern gives higher transmission haze compared to nanodimple pattern. By controlling the ratio of pattern depth/height to pitch of the features on these surfaces, both an increase in optical haze and a balance between total reflection intensity and total transmission intensity can be achieved.

  • RESEARCH ARTICLE
    Exceptional point enhanced nanoparticle detection in deformed Reuleaux-triangle microcavity
    Jinhao Fei, Xiaobei Zhang, Qi Zhang, Yong Yang, Zijie Wang, Chuanlu Deng, Yi Huang, Tingyun Wang
    Frontiers of Optoelectronics, 2024, 17(3): 27. https://doi.org/10.1007/s12200-024-00131-5

    In this paper, we propose a deformed Reuleaux-triangle resonator (RTR) to form exceptional point (EP) which results in the detection sensitivity enhancement of nanoparticle. After introducing single nanoparticle to the deformed RTR at EP, frequency splitting obtains an enhancement of more than 6 times compared with non-deformed RTR. In addition, EP induced a result that the far field pattern of chiral mode responses significantly to external perturbation, corresponding to the change in internal chirality. Therefore, single nanoparticle with far distance of more than 4000 nm can be detected by measuring the variation of far field directional emission. Compared to traditional frequency splitting, the far field pattern produced in deformed RTR provides a cost-effective and convenient path to detect single nanoparticle at a long distance, without using tunable laser and external coupler. Our structure indicates great potential in high sensitivity sensor and label-free detector.

  • RESEARCH ARTICLE
    Stereoscopic spatial graphical method of Mueller matrix: Global-Polarization Stokes Ellipsoid
    Xinxian Zhang, Jiawei Song, Jiahao Fan, Nan Zeng, Honghui He, Valery V. Tuchin, Hui Ma
    Frontiers of Optoelectronics, 2024, 17(3): 29. https://doi.org/10.1007/s12200-024-00132-4

    A Mueller matrix covers all the polarization information of the measured sample, however the combination of its 16 elements is sometimes not intuitive enough to describe and identify the key characteristics of polarization changes. Within the Poincaré sphere system, this study achieves a spatial representation of the Mueller matrix: the Global-Polarization Stokes Ellipsoid (GPSE). With the help of Monte Carlo simulations combined with anisotropic tissue models, three basic characteristic parameters of GPSE are proposed and explained, where the V parameter represents polarization maintenance ability, and the E and D parameters represent the degree of anisotropy. Furthermore, based on GPSE system, a dynamic analysis of skeletal muscle dehydration process demonstrates the monitoring effect of GPSE from an application perspective, while confirming its robustness and accuracy.

  • CORRECTION
    Correction: Control of visible-range transmission and reflection haze by varying pattern size, shape and depth in flexible metasurfaces
    Avijit Maity, Vaswati Biswas, R. Vijaya
    Frontiers of Optoelectronics, 2024, 17(3): 30. https://doi.org/10.1007/s12200-024-00135-1
  • RESEARCH ARTICLE
    Plasma photonic crystal ‘kaleidoscope’ with flexible control of topology and electromagnetism
    Jing Wang, Shuang Liu, Weili Fan, Shuo Wang, Cuicui Lu, Yafeng He, Fucheng Liu, Xiaoyong Hu
    Frontiers of Optoelectronics, 2024, 17(4): 34. https://doi.org/10.1007/s12200-024-00137-z

    Continuous development of photonic crystals (PCs) over the last 30 years has carved out many new scientific frontiers. However, creating tunable PCs that enable flexible control of geometric configurations remains a challenge. Here we present a scheme to produce a tunable plasma photonic crystal (PPC) ‘kaleidoscope’ with rich diversity of structural configurations in dielectric barrier discharge. Multi-freedom control of the PPCs, including the symmetry, dielectric constant, crystal orientation, lattice constant, topological state, and structures of scattering elements, has been realized. Four types of lattice reconfigurations are demonstrated, including transitions from periodic to periodic, disordered to ordered, non-topological to topological, and striped to honeycomb Moiré lattices. Furthermore, alterations in photonic band structures corresponding to the reconstruction of various PPCs have been investigated. Our system presents a promising platform for generating a PPC ‘kaleidoscope’, offering benefits such as reduced equipment requirements, low cost, rapid response, and enhanced flexibility. This development opens up new opportunities for both fundamental and applied research.

  • RESEARCH ARTICLE
    Mueller matrix polarimetry for quantitative evaluation of the Achilles tendon injury recovery
    Huibin Yang, Minhui Xu, Honghui He, Nan Zeng, Jiawei Song, Tongyu Huang, Ziyang Liang, Hui Ma
    Frontiers of Optoelectronics, 2024, 17(4): 39. https://doi.org/10.1007/s12200-024-00142-2

    Achilles tendon injuries, as a widely existing disease, have attracted a lot of research interest. Mueller matrix polarimetry, as a novel label-free quantitative imaging method, has been widely used in various applications of lesion identification and pathological diagnosis. However, focusing on the recovery process of Achilles tendon injuries, current optical imaging methods have not yet achieved the label-free precise identification and quantitative evaluation. In this study, using Mueller matrix polarimetry, various Achilles tendon injury samples were characterized specifically, and the efficacy of different recovery schemes was evaluated accordingly. Experiments indicate that injured Achilles tendons show less phase retardance, larger diattenuation, and relatively disordered orientation. The combination of experiments with Monte Carlo simulation results illustrate the microscopic mechanism of the Achilles tendon recovery process from three aspects, that is, the increased fiber diameter, a more consistent fiber orientation, and greater birefringence induced by more collagen protein. Finally, based on the statistical distribution of polarization measurements, a polarization specific characterization parameter was extracted to construct a label-free image, which cannot only intuitively show the injury and recovery of Achilles tendon samples, but also give a quantitative evaluation of the treatment.

  • RESEARCH ARTICLE
    Vehicular Mini-LED backlight display inspection based on residual global context mechanism
    Guobao Zhao, Xi Zheng, Xiao Huang, Yijun Lu, Zhong Chen, Weijie Guo
    Frontiers of Optoelectronics, 2024, 17(4): 35. https://doi.org/10.1007/s12200-024-00140-4

    Mini-LED backlight has emerged as a promising technology for high performance LCDs, yet the massive detection of dead pixels and precise LEDs placement are constrained by the miniature scale of the Mini-LEDs. The high-resolution network (Hrnet) with mixed dilated convolution and dense upsampling convolution (MDC-DUC) module and a residual global context attention (RGCA) module has been proposed to detect the quality of vehicular Mini-LED backlights. The proposed model outperforms the baseline networks of Unet, Pspnet, Deeplabv3+, and Hrnet, with a mean intersection over union (Miou) of 86.91%. Furthermore, compared to the four baseline detection networks, our proposed model has a lower root-mean-square error (RMSE) when analyzing the position and defective count of Mini-LEDs in the prediction map by canny algorithm. This work incorporates deep learning to support production lines improve quality of Mini-LED backlights.

  • RESEARCH ARTICLE
    Multi-octave two-color soliton frequency comb in integrated chalcogenide microresonators
    Huanjie Cheng, Guosheng Lin, Di Xia, Liyang Luo, Siqi Lu, Changyuan Yu, Bin Zhang
    Frontiers of Optoelectronics, 2024, 17(4): 36. https://doi.org/10.1007/s12200-024-00139-x

    Mid-infrared (MIR) Kerr microcombs are of significant interest for portable dual-comb spectroscopy and precision molecular sensing due to strong molecular vibrational absorption in the MIR band. However, achieving a compact, octave-spanning MIR Kerr microcomb remains a challenge due to the lack of suitable MIR photonic materials for the core and cladding of integrated devices and appropriate MIR continuous-wave (CW) pump lasers. Here, we propose a novel slot concentric dual-ring (SCDR) microresonator based on an integrated chalcogenide glass chip, which offers excellent transmission performance and flexible dispersion engineering in the MIR band. This device achieves both phase-matching and group velocity matching in two separated anomalous dispersion regions, enabling phase-locked, two-color solitons in the MIR region with a commercial 2-μm CW laser as the pump source. Moreover, the spectral locking of the two-color soliton enhances pump wavelength selectivity, providing precise control over soliton dynamics. By leveraging the dispersion characteristics of the SCDR microresonator, we have demonstrated a multi-octave-spanning, two-color soliton microcomb, covering a spectral range from 1156.07 to 5054.95 nm (200 THz) at a -40 dB level, highlighting the versatility and broad applicability of our approach. And the proposed multi-octave MIR frequency comb is relevant for applications such as dual-comb spectroscopy and trace-gas sensing.

  • COMMENT
    Optical logic array: a photonic solution towards universal computing
    Lu Fang
    Frontiers of Optoelectronics, 2024, 17(4): 40. https://doi.org/10.1007/s12200-024-00145-z
  • RESEARCH ARTICLE
    Influence of the homotopy stability perturbation on physical variations of non-local opto-electronic semiconductor materials
    A. El-Dali, Mohamed I. A. Othman
    Frontiers of Optoelectronics, 2024, 17(4): 38. https://doi.org/10.1007/s12200-024-00141-3

    In the current work, we investigate a novel technique specialized in stability perturbation theory to analyze the primary variations such as thermal, carrier, elastic, and mechanical waves in photothermal theory. The interface of the non-local semiconductor material is utilized to study the stability analysis. The problem is established using a 1D opto-electronic-thermoelastic deformation in the context of the photo-thermoelasticity (PTE) framework. The Laplace transform method is used to convert the system from the time domain into the frequency domain, and the boundary conditions for the thermal, elastic, and plasma waves are applied to the interface of the medium. The homotopy perturbation method was used as an innovative approach to analyze the stability of the non-local silicon’s primary physical fields. The numerical inversion method is applied, yielding many graphs focusing on important numerical factors such as non-local effects, thermo-energy, and thermo-electric coupling parameters. Investigating dual solutions between stable and unstable regions for critical parameters like thermo-electric and thermo-energy coupling factors demonstrates that the homotopy perturbation technique can effectively analyze the stability analysis. The comparison between silicon and germanium is illustrated graphically. Utilizing the homotopy perturbation technique, we can effectively examine the stability of the primary physical variations with the effect of some values for eigenvalues approaches.