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Fiber Optics and Optical Communications
Kang-Jie Lim
Samuel Kai-Wen Seah
Joash Yong’En Ye
Wendy Weiying Lim
Chu-Perng Seah
Yunn-Boon Tan
Suting Tan
Huiting Lim
Raghuraman Sidharthan
Arumugam Rajendra Prasadh
Chen-Jian Chang
Seongwoo Yoo
Song-Liang Chua
摘要 + 此论文可免费阅读 (可能需要登录) A short absorption length ytterbium (Yb)-doped large-mode area (LMA) fiber is presented as a step forward to mitigate the stern problem of nonlinear scatterings in a tandem pumping scheme adopted for high-power fiber laser. The short absorption length was realized by incorporating high Yb concentration in the fiber core. Furthermore, by replacing the inherent silica cladding with a Ge-doped cladding, we were able to obtain low core numerical aperture (NA) and negate the detrimental effect of index-raising by high Yb concentrations. This overcomes the long-standing limitation in step-index Yb-doped fibers (YDFs) where high cladding absorption inevitably results in high NA, thus hampering single-mode operation. We report an LMA () YDF with NA of 0.04 and absorption of 27 dB/m at 976 nm—both traits promote power scaling of single-mode tandem pumped fiber lasers. To our knowledge, this is the highest cladding absorption attained in a low-NA step-index fiber to date. An all-fiber tandem-pumped amplifier was built using only of the YDF. The amplifier delivered a near-Gaussian beam () at 836 W output power (pump power limited) with a high slope efficiency of . Thanks to the short length and the tandem pumping, no indication of limiting factors such as stimulated Raman scattering, photodarkening, and transverse mode instability was observed. PDF全文   HTML全文 Photonics Research, 2020年第8卷第10期 pp.1599-1604   
Image Processing and Image Analysis
Zhenyu Zhou
Jun Xia
Jun Wu
Chenliang Chang
Xi Ye
Shuguang Li
Bintao Du
Hao Zhang
Guodong Tong
摘要 + 此论文可免费阅读 (可能需要登录) Phase imaging always deals with the problem of phase invisibility when capturing objects with existing light sensors. However, there is a demand for multiplane full intensity measurements and iterative propagation process or reliance on reference in most conventional approaches. In this paper, we present an end-to-end compressible phase imaging method based on deep neural networks, which can implement phase estimation using only binary measurements. A thin diffuser as a preprocessor is placed in front of the image sensor to implicitly encode the incoming wavefront information into the distortion and local variation of the generated speckles. Through the trained network, the phase profile of the object can be extracted from the discrete grains distributed in the low-bit-depth pattern. Our experiments demonstrate the faithful reconstruction with reasonable quality utilizing a single binary pattern and verify the high redundancy of the information in the intensity measurement for phase recovery. In addition to the advantages of efficiency and simplicity compared to now available imaging methods, our model provides significant compressibility for imaging data and can therefore facilitate the low-cost detection and efficient data transmission. PDF全文   HTML全文 Photonics Research, 2020年第8卷第10期 pp.1624-1633   
Imaging Systems, Microscopy, and Displays
Luocheng Huang
James Whitehead
Shane Colburn
Arka Majumdar
摘要 + 此论文可免费阅读 (可能需要登录) Metasurface optics have demonstrated vast potential for implementing traditional optical components in an ultracompact and lightweight form factor. Metasurfaces, however, suffer from severe chromatic aberrations, posing serious limitations on their practical use. Existing approaches for circumventing this involving dispersion engineering are limited to small apertures and often entail multiple scatterers per unit cell with small feature sizes. Here, we present an alternative technique to mitigate chromatic aberration and demonstrate high-quality, full-color imaging using extended depth of focus (EDOF) metalenses and computational reconstruction. Previous EDOF metalenses have relied on cubic phase masks, where the image quality suffers from asymmetric artefacts. Here we demonstrate the use of rotationally symmetric masks, including logarithmic-aspherical, and shifted axicon masks, to mitigate this problem. Our work will inspire further development in achromatic metalenses beyond dispersion engineering and hybrid optical–digital metasurface systems. PDF全文   HTML全文 Photonics Research, 2020年第8卷第10期 pp.1613-1623   
Integrated Optics
Jinfeng Mu
Meindert Dijkstra
Jeroen Korterik
Herman Offerhaus
Sonia M. García-Blanco
摘要 + 此论文可免费阅读 (可能需要登录) Silicon nitride attracts increasing interest in integrated photonics owing to its low propagation loss and wide transparency window, extending from to 2350 nm. Scalable integration of active devices such as amplifiers and lasers on the platform will enable applications requiring optical gain and a much-needed alternative to hybrid integration, which suffers from high cost and lack of high-volume manufacturability. We demonstrate a high-gain optical amplifier in monolithically integrated on the platform using a double photonic layer approach. The device exhibits a net gain of at 1532 nm, and a broadband gain operation over 70 nm covering wavelengths in the S-, C- and L-bands. This work shows that rare-earth-ion-doped materials and in particular, rare-earth-ion-doped , can provide very high net amplification for the platform, paving the way to the development of different active devices monolithically integrated in this passive platform. PDF全文   HTML全文 Photonics Research, 2020年第8卷第10期 pp.1634-1641   
Lasers and Laser Optics
Yi Zhou
Yu-Xuan Ren
Jiawei Shi
Kenneth K. Y. Wong
摘要 + 此论文可免费阅读 (可能需要登录) Soliton explosions, among the most exotic dynamics, have been extensively studied on parameter invariant stationary solitons. However, the explosion dynamics are still largely unexplored in breathing dissipative solitons as a dynamic solution to many nonlinear systems. Here, we report on the first observation of a breathing dissipative soliton explosion in a net-normal-dispersion bidirectional ultrafast fiber laser. The breathing soliton explosions could be stimulated by the soliton buildup process or alteration of polarization settings. Transient breathing soliton pairs with intensive repulsion that is sensitive to initial conditions can also be triggered by multiple soliton explosions in the soliton buildup process instead of being triggered by varying polarization settings. The high behavior similarity also exists in the breathing soliton buildup and explosion process owing to the common gain and loss modulation. In addition, dissipative rogue waves were detected in the breathing soliton explosion, and the collision of breathing soliton significantly enhanced the amplitude of rogue waves, which is characteristic of the breathing solitons in a bidirectional fiber laser. These results shed new insights into complex dissipative soliton dynamics. PDF全文   HTML全文 Photonics Research, 2020年第8卷第10期 pp.1566-1572  
Yuwei Zhao
Jintao Fan
Youjian Song
Uwe Morgner
Minglie Hu
摘要 + 此论文可免费阅读 (可能需要登录) Internal motions in femtosecond soliton molecules provide insight into universal collective dynamics in various nonlinear systems. Here we introduce an orbital-angular-momentum (OAM)-resolved method that maps the relative phase motion within a femtosecond soliton molecule into the rotational movement of the interferometric beam profile of two optical vortices. By this means, long-term relative phase evolutions of doublet and triplet soliton molecules generated in an all-polarization-maintaining mode-locked Er-fiber laser are revealed. This simple and practical OAM-resolved method represents a promising way to directly visualize the complex phase dynamics in a diversity of multisoliton structures. PDF全文   HTML全文 Photonics Research, 2020年第8卷第10期 pp.1580-1585  
Xin-Xia Gao
Jin-Ming Cui
Zhi-Hao Hu
Chun-Hua Dong
Jian Wang
Yun-Feng Huang
Chuan-Feng Li
Guang-Can Guo
摘要 + 此论文可免费阅读 (可能需要登录) A narrow-linewidth laser operating at the telecommunications band combined with both fast and wide-band tuning features will have promising applications. Here we demonstrate a single-mode (both transverse and longitudinal mode) continuous microlaser around 1535 nm based on a fiber Fabry–Pérot microcavity, which achieves wide-band tuning without mode hopping to the 1.3 THz range and fast tuning rate to 60 kHz and yields a frequency scan rate of . Moreover, the linewidth of the laser is measured as narrow as 3.1 MHz. As the microlaser combines all these features into one fiber component, it can serve as the seed laser for versatile applications in optical communication, sensing, frequency-modulated continuous-wave radar, and high-resolution imaging. PDF全文   HTML全文 Photonics Research, 2020年第8卷第10期 pp.1642-1647   
Nanophotonics and Photonic Crystals
Zhexin Zhao
Dylan S. Black
R. Joel England
Tyler W. Hughes
Yu Miao
Olav Solgaard
Robert L. Byer
Shanhui Fan
摘要 + 此论文可免费阅读 (可能需要登录) To be useful for most scientific and medical applications, compact particle accelerators will require much higher average current than enabled by current architectures. For this purpose, we propose a photonic crystal architecture for a dielectric laser accelerator, referred to as a multi-input multi-output silicon accelerator (MIMOSA), that enables simultaneous acceleration of multiple electron beams, increasing the total electron throughput by at least 1 order of magnitude. To achieve this, we show that the photonic crystal must support a mode at the point in reciprocal space, with a normalized frequency equal to the normalized speed of the phase-matched electron. We show that the figure of merit of the MIMOSA can be inferred from the eigenmodes of the corresponding infinitely periodic structure, which provides a powerful approach to design such devices. Additionally, we extend the MIMOSA architecture to electron deflectors and other electron manipulation functionalities. These additional functionalities, combined with the increased electron throughput of these devices, permit all-optical on-chip manipulation of electron beams in a fully integrated architecture compatible with current fabrication technologies, which opens the way to unconventional electron beam shaping, imaging, and radiation generation. PDF全文   HTML全文 Photonics Research, 2020年第8卷第10期 pp.1586-1598   
Optical and Photonic Materials
Qionghua Mo
Tongchao Shi
Wensi Cai
Shuangyi Zhao
Dongdong Yan
Juan Du
Zhigang Zang
摘要 + 此论文可免费阅读 (可能需要登录) All-inorganic cesium lead bromide () perovskite quantum dots (QDs) with excellent optical properties have been regarded as good gain materials for amplified spontaneous emission (ASE). However, the poor stability as the results of the high sensitivity to heat and moisture limits their further applications. Here, we report a facile one-pot approach to synthesize QDs at room temperature. Due to the effective defects passivation using , as-prepared QDs present an enhanced photoluminescence quantum yield (PLQY) and chemical stability. The PLQY of QDs reaches 71.6% which is higher than 46% in pure QDs. The PL intensity of QDs maintains 84% while remaining 24% in pure after 80 min heating at 60°C. The ASE performance of the films is also studied under a two-photon-pumped laser. Compared with the films using pure QDs, those with as-prepared QDs exhibit a reduced threshold of ASE. The work suggests that room-temperature-synthesized -coated perovskites QDs are promising candidates for laser devices. PDF全文   HTML全文 Photonics Research, 2020年第8卷第10期 pp.1605-1612   
Optical Devices
Jun Ma
Yang He
Xue Bai
Li-Peng Sun
Kai Chen
Kyunghwan Oh
Bai-Ou Guan
摘要 + 此论文可免费阅读 (可能需要登录) Interaction of acoustic waves and microbubbles occurs in numerous biomedical applications including ultrasound imaging, drug delivery, lithotripsy treatment, and cell manipulation, wherein the acoustically driven microbubbles routinely act as active microscale oscillators or actuators. In contrast, microbubbles were utilized here as passive receivers to detect broadband ultrasound waves in aqueous environments. The microbubble was photothermally generated on a microstructured optical fiber (MOF) tip, forming a flexible Fabry–Pérot cavity whose gas–water interface was sensitive to ultrasound waves. The MOF severed as both a low-loss waveguide and a compact light condenser, allowing high-efficiency generation and stabilization of ultrasmall microbubbles. Integrated with all-fiber interferometry, a 10 μm diameter microbubble exhibited a low noise-equivalent pressure level of and a broad bandwidth of , capable of detecting weak ultrasounds emitted from red blood cells irradiated by pulsed laser light. With advantages of high sensitivity, compact size, and low cost, the microbubble-based ultrasound sensor has great potential in biomedical imaging and sensing applications. PDF全文   HTML全文 Photonics Research, 2020年第8卷第10期 pp.1558-1565   
Quantum Optics
Kaimin Zheng
Minghao Mi
Ben Wang
Liang Xu
Liyun Hu
Shengshuai Liu
Yanbo Lou
Jietai Jing
Lijian Zhang
摘要 + 此论文可免费阅读 (可能需要登录) Quantum stochastic phase estimation has many applications in the precise measurement of various physical parameters. Similar to the estimation of a constant phase, there is a standard quantum limit for stochastic phase estimation, which can be obtained with the Mach–Zehnder interferometer and coherent input state. Recently, it has been shown that the stochastic standard quantum limit can be surpassed with nonclassical resources such as squeezed light. However, practical methods to achieve quantum enhancement in the stochastic phase estimation remain largely unexplored. Here we propose a method utilizing the SU(1,1) interferometer and coherent input states to estimate a stochastic optical phase. As an example, we investigate the Ornstein–Uhlenback stochastic phase. We analyze the performance of this method for three key estimation problems: prediction, tracking, and smoothing. The results show significant reduction of the mean square error compared with the Mach–Zehnder interferometer under the same photon number flux inside the interferometers. In particular, we show that the method with the SU(1,1) interferometer can achieve fundamental quantum scaling, achieve stochastic Heisenberg scaling, and surpass the precision of the canonical measurement. PDF全文   HTML全文 Photonics Research, 2020年第8卷第10期 pp.1653-1661   
Research Articles
JungYun Han
Andrey A. Sukhorukov
Daniel Leykam
摘要 + 此论文可免费阅读 (可能需要登录) We predict the preservation of temporal indistinguishability of photons propagating through helical coupled-resonator optical waveguides (H-CROWs). H-CROWs exhibit a pseudospin-momentum locked dispersion, which we show suppresses on-site disorder-induced backscattering and group velocity fluctuations. We simulate numerically the propagation of two-photon wave packets, demonstrating that they exhibit almost perfect Hong–Ou–Mandel dip visibility and then can preserve their quantum coherence even in the presence of moderate disorder, in contrast with regular CROWs, which are highly sensitive to disorder. As indistinguishability is the most fundamental resource of quantum information processing, H-CROWs may find applications for the implementation of robust optical links and delay lines in the emerging quantum photonic communication and computational platforms. PDF全文   HTML全文 Photonics Research, 2020年第8卷第10期 pp.B15-24  
Yang Li
Chao Liang
Gaopeng Wang
Jielei Li
Shi Chen
Shihe Yang
Guichuan Xing
Hui Pan
摘要 + 此论文可免费阅读 (可能需要登录) Modifying the surface of poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA) with toluene during the high-speed spin-coating process of dimethylformamide considerably improves the wettability and morphology of PTAA and results in improvement of the crystallinity and absorption of perovskite film. The hole mobility and ohm contact have also been improved accordingly. Combined with these improved parameters, inverted perovskite solar cells with high efficiency of 19.13% and long-term stability could be achieved, which are much better than those with untreated PTAA. Importantly, our devices can keep 88.4% of the initial power conversion efficiency after 30 days of storage in ambient air. PDF全文   HTML全文 Photonics Research, 2020年第8卷第10期 pp.A39-49  
Michal Baranowski
Paulina Plochocka
Rui Su
Laurent Legrand
Thierry Barisien
Frederick Bernardot
Qihura Xiong
Christophe Testelin
Maria Chamarro
摘要 + 此论文可免费阅读 (可能需要登录) High magnetic field spectroscopy has been performed on lead chloride-based perovskite, a material that attracts significant interest for photovoltaic and photonic applications within the past decades. Optical properties being mainly driven by the exciton states, we have measured the fundamental parameters, such as the exciton binding energy, effective mass, and dielectric constant. Among the inorganic halide perovskites, owns the largest exciton binding energy and effective mass. This blue emitting compound has also been compared with lower band gap energy perovskites and other semiconducting phases, showing comparable band gap dependences for binding energy and Bohr radius. PDF全文   HTML全文 Photonics Research, 2020年第8卷第10期 pp.A50-55   
Silicon Photonics
Aditya Malik
Joel Guo
Minh A. Tran
Geza Kurczveil
Di Liang
John E. Bowers
摘要 + 此论文可免费阅读 (可能需要登录) Heterogeneously integrated lasers in the O-band are a key component in realizing low-power optical interconnects for data centers and high-performance computing. Quantum-dot-based materials have been particularly appealing for light generation due to their ultralow lasing thresholds, small linewidth enhancement factor, and low sensitivity to reflections. Here, we present widely tunable quantum-dot lasers heterogeneously integrated on silicon-on-insulator substrate. The tuning mechanism is based on Vernier dual-ring geometry, and a 47 nm tuning range with 52 dB side-mode suppression ratio is observed. These parameters show an increase to 52 nm and 58 dB, respectively, when an additional wavelength filter in the form of a Mach–Zehnder interferometer is added to the cavity. The Lorentzian linewidth of the lasers is measured as low as 5.3 kHz. PDF全文   HTML全文 Photonics Research, 2020年第8卷第10期 pp.1551-1557  
Zhi Liu
Xiuli Li
Chaoqun Niu
Jun Zheng
Chunlai Xue
Yuhua Zuo
Buwen Cheng
摘要 + 此论文可免费阅读 (可能需要登录) A high-speed evanescent-coupled Ge waveguide electro-absorption modulator (EAM) with simple fabrication processes was realized on a silicon-on-insulator platform with a 220 nm top Si layer. Selectively grown Ge with a triangle shape was directly used for Ge waveguides of the EAM. An asymmetric p-i-n junction was designed in the Ge waveguide to provide a strong electric field for Franz–Keldysh effect. The insertion loss of the Ge EAM was 6.2 dB at 1610 nm. The EAM showed the high electro-optic bandwidth of 36 GHz at . Clear open 56 Gbps eye diagrams were observed at 1610 nm with a dynamic extinction ratio of 2.7 dB and dynamic power consumption of 45 fJ/bit for voltage swing of 3Vpp. PDF全文   HTML全文 Photonics Research, 2020年第8卷第10期 pp.1648-1652   
Surface Optics and Plasmonics
Li Long
Jianfeng Chen
Huakang Yu
Zhi-Yuan Li
摘要 + 此论文可免费阅读 (可能需要登录) Tip-enhanced Raman spectroscopy (TERS) offers a powerful means to enhance the Raman scattering signal of a molecule as the localized surface plasmonic resonance will induce a significant local electric field enhancement in the nanoscale hot spot located within the nanogap of the TERS system. In this work, we theoretically show that this nanoscale hot spot can also serve as powerful optical tweezers to tightly trap a molecule. We calculate and analyze the local electric field and field gradient distribution of this nanogap plasmon hot spot. Due to the highly localized electric field, a three-dimensional optical trap can form at the hot spot. Moreover, the optical energy density and optical force acting on a molecule can be greatly enhanced to a level far exceeding the conventional single laser beam optical tweezers. Calculations show that for a single organic molecule, which is modeled as a spherical molecule with a radius of , a dielectric coefficient , and a polarizability , the stiffness of the hot-spot trap can reach a high value of about and in the direction perpendicular and parallel to the TERS tip axis, which is far larger than the stiffness of single-beam tweezers, . This hard-stiffness will enable the molecules to be stably captured in the plasmon hot spot. Our results indicate that TERS can become a promising tool of optical tweezers for trapping a microscopic object like molecules while implementing Raman spectroscopic imaging and analysis at the same time. PDF全文   HTML全文 Photonics Research, 2020年第8卷第10期 pp.1573-1579   |