Ding Zi-xuan   Huang Zi-nan   Chen Ye   Mou Chengbo   Lu Yanqing   Xu Fei  

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Ultrafast lasers generating high repetition rate ultrashort pulses through various mode-locking methods can benefit many important applications including communication, materials processing, astronomical observation, etc. For decades, mode-locking based on dissipative four-wave-mixing (DFWM) has been fundamental in producing pulses with repetition rates on the order of gigahertz (GHz), where multiwavelength comb filters and long nonlinear components are elemental. Recently, this method has been improved using filter-driven DFWM, which exploits both the filtering and nonlinear features of silica microring resonators. However, the fabrication complexity and coupling loss between waveguides and fibers are problematics. In this study, we demonstrate a tens to hundreds of gigahertz stable pulsed all-fiber laser based on the hybrid plasmonic microfiber knot resonator device. Unlike previously reported pulse generation mechanisms, the operation utilizes the nonlinear-polarization-rotation (NPR) effect introduced by the polarization-dependent feature of the device to increase intracavity power for boosting DFWM mode-locking, which we term NPR -stimulated DFWM. The easily-fabricated versatile device acts as a polarizer, comb filter, and nonlinear component simultaneously, thereby introducing a novel application of microfiber resonator devices in ultrafast and nonlinear photonics. We believe that our work underpins a significant improvement in achieving practical low-cost ultrafast light sources.

       PDF全文 (下载：0)        Advanced Photonics ，年第卷第期 pp.      

Lim Joowon   Ayoub Ahmed   Psaltis Demetri  

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We accurately reconstruct 3D refractive index (RI) distributions from highly ill-posed 2D measurements using a deep neural network (DNN). Strong distortions are introduced on reconstructions obtained by the Wolf transform inversion method due to the ill-posed measurements acquired from the limited numerical apertures (NAs) of the optical system. Despite the recent success of DNNs on solving ill-posed inverse problems, the application to 3D optical imaging is particularly challenging due to the lack of ground truth. We overcome this limitation by generating digital phantoms which serve as samples for the discrete dipole approximation (DDA) to generate multiple 2D projection maps for a limited range of illumination angles. The samples presented in this work are red blood cells (RBCs), which are highly affected by the ill-posedness due to their morphology. The trained network using synthetic measurements from the digital phantoms successfully eliminates the introduced distortions. Most importantly, we obtained high fidelity reconstructions from experimentally recorded projections of real RBC sample using the network that was trained on digitally generated RBC phantoms. Finally, we confirmed the reconstruction accuracy using the DDA to calculate the 2D projections of the 3D reconstructions and compared them to the experimentally recorded projections.

       PDF全文 (下载：0)        Advanced Photonics ，年第卷第期 pp.      

Zhu Tengfeng   Huang Junyi   Ruan Zhichao  

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Phase is a fundamental resource for optical imaging but cannot be directly observed with intensity measurements. The existing methods to quantify a phase distribution rely on complex devices and structures and lead to the difficulties of optical alignment and adjustment. Here we experimentally demonstrate a phase mining method based on so-called adjustable spatial differentiation, just generally by analyzing the polarization in light reflection on a single planar dielectric interface. With introducing an adjustable bias, we create a virtual light source to render the measured images with a shadow-cast effect. From the virtual shadowed images, we can further recover the phase distribution of a transparent object with the accuracy of 0.05λ RMS. Without any dependence on resonance or material dispersion, this method directly stems from the intrinsic properties of light and can be generally extended to a board frequency range.

       PDF全文 (下载：1)        Advanced Photonics ，年第卷第期 pp.      

Song yufeng   Wang Zhenhong   wang cong   Panajotov Krassimir   Zhang Han  

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Rogue waves (RWs) are considered as rare extreme localized wave packets, which has received much interest in recent decade. Optical RWs are extreme and rare optical waves appear suddenly in an optical system. Owing to the abundant nonlinear dynamics, dissipative RWs generation in fiber lasers were recently numerically predicted and experimentally verified. In this contribution, we presented a brief review on the experimental study of optical RWs generation, especially in the fiber lasers. Rogue wave generation in fiber lasers attributed to different mechanism was summarized and study of optical rogue wave in the future is also introduced.

       PDF全文 (下载：0)        Advanced Photonics ，年第卷第期 pp.      

Jin Qi   E Yiwen   Gao Shenghan   Zhang XiCheng  

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Optically induced terahertz wave generation from air plasma generally requires a short temporal laser pulse. In contrast, it was observed that terahertz radiation from water prefers a longer pulse, wherein the mechanism remains unclear. Here, we attribute the preference toward longer pulse duration to the process of plasma formation in water, which is supported by a numerical simulation result showing that the highest electron density is achieved with a sub-picosecond pulse. The explanation is further verified by the coincidence of our experimental result and the simulation when the thickness of the water is varied. Other liquids are also tested to assure the preference for such a pulse is not exclusive to water.

       PDF全文 (下载：0)        Advanced Photonics ，年第卷第期 pp.      

Qi Dalong   Yang Chengshuai   He Yilin   Cao Fengyan   Yao Jiali   Ding Pengpeng   Gao Liang   Jia Tianqing   Sun Zhenrong   Liang Jinyang   Zhang Shian   Wang Lihong  

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Compressed ultrafast photography (CUP) is a burgeoning single-shot computational imaging technique that provides an imaging speed as high as 10 trillion frames per second and a sequence depth of up to a few hundred frames. This technique synergizes compressed sensing and the streak camera technique to capture non-repeatable ultrafast transient events with a single shot. With recent unprecedented technical developments and extensions of this methodology, it has been widely used in ultrafast optical imaging and metrology, ultrafast electron diffraction and microscopy, and information security protection. Here, we review the basic principles of CUP, its recent advances in data acquisition and image reconstruction, its fusions with other modalities, and its unique applications in multiple research fields.

       PDF全文 (下载：1)        Advanced Photonics ，年第卷第期 pp.      

Zayats Anatoly   Yuan Xiao-Cong (Larry)  

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Advanced Photonics: one year on

       PDF全文 (下载：1)        Advanced Photonics ，年第卷第期 pp.      

yu yang   Xiao Ting- Hui   wu yunzhao   Li Wanjun   Zeng Qing-Guang   long li   Li Zhiyuan  

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Single-molecule surface-enhanced Raman spectroscopy (SERS) is a powerful vibrational spectroscopic technique that enables high-content chemical analysis of molecules with an ultrahigh sensitivity up to the single-molecule level. The last two decades have witnessed a great number of breakthroughs and advances in single-molecule SERS by virtue of rapid development of nanotechnology. Here we make a comprehensive and compact review of recent research progress on single-molecule SERS. Specifically, we discuss basic concepts and fundamental points that need to be taken care of for implementation of single-molecule SERS. The recently developed strategies for realizing single-molecule SERS as well as several novel applications of single-molecule SERS are also summarized and discussed. Finally, we clarify the challenges currently faced in single-molecule SERS and point out their perspectives of solution. We hope this review will provide a relatively complete picture of single-molecule SERS at the current stage and inspire the future advancement of single-molecule SERS.

       PDF全文 (下载：3)        Advanced Photonics ，年第卷第期 pp.      

Qin Zhipeng   Xie Guoqiang   Gu Hongan   Hai Ting   Yuan Peng   Ma Jingui   Qian Liejia  

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The mode-locked fluoride fiber laser (MLFFL) is an exciting platform for directly generating ultra-short pulses in the mid-infrared (mid-IR). However, owing to difficulty in managing the dispersion in fluoride fiber lasers, MLFFLs are restricted to the soliton regime, hindering pulse-energy scaling. Here, we overcame the problem of dispersion management by utilizing the huge normal dispersion generated near the absorption edge of an infrared-bandgap semiconductor, and promoted MLFFL from soliton to breathing-pulse mode-locking. In the breathing-pulse regime, the accumulated nonlinear phase shift can be significantly reduced in the cavity, and the pulse-energy-limitation effect is mitigated. The breathing-pulse MLFFL directly produced a pulse energy of 9.3 nJ and pulse duration of 215 fs, with a record peak power of 43.3 kW at 2.8 μm. Our work paves the way for the pulse-energy and peak-power scaling of mid-IR fluoride fiber lasers, enabling a wide range of applications.

       PDF全文 (下载：3)        Advanced Photonics ，年第卷第期 pp.      

Zhang Xueqian   Xu Quan   Xia Lingbo   Li Yanfeng   Gu Jianqiang   Tian zhen   Ouyang Chunmei   Han JiaGuang   Zhang Weili  

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Terahertz science and technology promise many cutting-edge applications. Terahertz surface plasmonic waves that propagate at metal-dielectric interfaces deliver a potential and effective way in realizing integrated terahertz devices and systems. Previous concern on terahertz surface plasmonic waves lied on their highly delocalized feature. However, recent advances in plasmonics indicate that the confinement of terahertz surface plasmonic waves, as well as their propagating behaviors, can also be engineered by designing the surface environments, shapes, structures, and materials, etc., enabling a unique and fascinating regime of plasmonic waves. Together with the essential spectral property of terahertz radiation, as well as the increasingly developed materials, micro-fabrication and time-domain spectroscopy technologies, devices and systems based on terahertz surface plasmonic waves may pave the way toward highly integrated platforms for multifunctional operation, implementation and processing of terahertz waves in both fundamental science and practical applications. Here, we present a review on terahertz surface plasmonic waves on various types of supports in a sequence of properties, excitation and detection, and applications. The current research trend and outlook of possible research directions of terahertz surface plasmonic waves are also outlined.

       PDF全文 (下载：0)        Advanced Photonics ，年第卷第期 pp.      

Rubin Shimon   Fainman Yeshaiahu  

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Optical metamaterials and metasurfaces which emerged in the course of the last few decades have revolutionized our understanding of light and light-matter interaction. While solid materials are naturally employed as key building elements for construction of optical metamaterials mainly due to their structural stability, practically no attention was given to study of liquid-made optical 2D metasurfaces and the underlying interaction regimes between surface optical modes and liquids. In this work, we theoretically demonstrate that surface plasmon polaritons and slab waveguide modes that propagate within a thin liquid dielectric film, trigger optical self-induced interaction facilitated by surface tension effects, which lead to formation of 2D optical liquid-made lattices/metasurfaces with tunable symmetry and which can be leveraged for tuning of lasing modes. Furthermore, we show that the symmetry breaking of the 2D optical liquid lattice leads to phase transition and tuning of its topological properties which allows to form, destruct and move Dirac-points in the k-space. Our results indicate that optical liquid lattices support extremely low lasing threshold relative to solid dielectric films and have the potential to serve as configurable analogous computation platform.

       PDF全文 (下载：3)        Advanced Photonics ，年第卷第期 pp.      

nguyen Minh   Nikolay Niko   Bradac Carlo   Kianinia Mehran   Ekimov Evgeny   Benson Oliver   aharonovich igor   mendelson Noah  

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Color centers in diamond—especially group IV defects—have been advanced as a viable solid-state platform for quantum photonics and information technologies. In this work, we investigate the photodynamics and characteristics of germanium-vacancy (GeV) centers hosted in high-pressure high temperature diamond nanocrystals. Through back-focal plane imaging, we analyze the far-field radiation pattern of the investigated emitters and derive a crossed-dipole emission, which is strongly aligned along one axis. We use this information in combination with lifetime measurements to extract the decay rate statistics of the GeV emitters and determine their quantum efficiency, which we estimated to be ~(22±2)%. Our results offer further insight into the photodynamic properties of the GeV center in nanodiamonds and confirm its suitability as a desirable system for quantum technologies.

       PDF全文 (下载：1)        Advanced Photonics ，年第卷第期 pp.      

LI JIAJI   Matlock Alex   li yunzhe   Chen Qian   Zuo Chao   Tian Lei  

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We demonstrate a label-free, scan-free <i>intensity</i> diffraction tomography technique utilizing annular illumination (aIDT) to rapidly characterize large-volume 3D refractive index distributions <i>in vitro</i>. By optimally matching the illumination geometry to the microscope pupil, our technique reduces the data requirement by 60x to achieve high-speed 10 Hz volume rates. Using 8 intensity images, we recover a 350×100×20μm³ volumes with near diffraction-limited lateral resolution of 487nm and axial resolution of 3.4 μm. Our technique’s large volume rate and high resolution enables 3D quantitative phase imaging of complex living biological samples across multiple length scales. We demonstrate aIDT’s capabilities on unicellular diatom microalgae, epithelial buccal cell clusters, and live <i>Caenorhabditis elegans</i> specimens. We recover macro-scale cellular structures, subcellular organelles, and dynamic micro-organism tissues with minimal motion artifacts. Quantifying such features has significant utility in oncology, immunology, and cellular pathophysiology, where changes to these structures can help detect disease, parasites, and evaluate new drug treatments. Finally, we evaluate our aIDT system’s accuracy and sensitivity through rigorous simulation. aIDT shows promise as a powerful high-speed, label-free computational microscopy technique for natural imaging applications evaluating environmental effects on a sample in real-time. We provide an open source implementation of aIDT with datasets in [1].

       PDF全文 (下载：2)        Advanced Photonics ，年第卷第期 pp.      

Martin Olivier  

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In this issue of Advanced Photonics, Zoé-Lise Deck-Léger et al. offer an extremely insightful analysis of such spacetime crystals, where the dielectric function is modulated periodically in space and time. Exploring all four dimensions of our environment is certainly vertiginous and quite confusing at best. The authors overcome this challenge by focusing on 2D spacetime crystals with periodicity in time and in one space dimension. This way, they are able to use concepts from special relativity and provide explicit pictorial representations of the different optical phenomena associated with simultaneous spatial and temporal periodicities.

       PDF全文 (下载：0)        Advanced Photonics ，年第卷第期 pp.      

ZHAO JIAN   Sun Yangyang   Zhu Hongbo   Zhu Zheyuan   Antonio-Lopez Jose E   Correa Rodrigo Amezcua   Pang Shuo   Schülzgen Axel  

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We demonstrate a deep-learning-based fiber imaging system that can transfer real-time artifact-free cell images through a meter-long Anderson localizing optical fiber for the first time. The cell samples are illuminated by an incoherent LED light source. A deep convolutional neural network is applied to the image reconstruction process. The network training uses data generated by a set-up with straight fiber at room temperature (~20 °C) but can be utilized directly for high fidelity reconstruction of cell images that are transported through fiber with a few degrees bend or fiber with segments heated up to 50 °C. In addition, cell images located several millimeters away from the bare fiber end can be transported and recovered successfully without the assistance of distal optics. We further evidence that the trained neural network is able to transfer its learning to recover images of cells featuring very different morphologies and classes that are never “seen” during the training process.

       PDF全文 (下载：5)        Advanced Photonics ，年第卷第期 pp.      

Narimanov Evgenii  

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The Abbe’s diffraction limit that relates the maximum optical resolution to the numerical aperture of the lenses involved and the optical wavelength, is generally considered as “a practical frontier that cannot be overcome with a conventional imaging system.” However, it does not represent a fundamental limit to the optical resolution, as demonstrated with several new imaging techniques that proved the possibility of finding the subwavelength information from the far-field of an optical image, from super-resolution fluorescence microscopy to the imaging systems that use new data processing algorithms leading to a dramatically improved resolution to super-oscillating metamaterial lenses. This raises the key question of whether there’s in fact a fundamental bound to the optical resolution – as opposed to “practical” limitations due to noise and imperfections, and if so then what it is. In this work, we derive the fundamental limit to the resolution of optical imaging, and demonstrate that, while a bound to the resolution of a fundamental nature does exit, contrary to the conventional wisdom it is neither exactly equal to nor necessarily close to Abbe’s estimate. Furthermore, our approach to imaging resolution that combines the tools from the physics of wave phenomena and the methods of information theory.

       PDF全文 (下载：2)        Advanced Photonics ，年第卷第期 pp.      

wang peng   Shen Xiong   Liu Jun   Li Ruxin  

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The temporal contrast is one of the most important parameters of an ultra-high intense laser pulse. Third-order auto-correlator or cross-correlator have been widely used to characterize the temporal contrast of an ultra-intense laser pulse in the past decades. Here, a novel and simple single-shot fourth-order auto-correlator to characterize the temporal contrast with higher time resolution and better pulse contrast fidelity in comparison to third-order correlators is proposed. The single-shot fourth-order autocorrelation consists of a frequency degenerate four-wave mixing process and a sum-frequency mixing process. The proof-of-principle experiments show that a dynamic range of approximately 10^11 compared with the noise level, a time resolution of approximately 160 fs, and a time window of 65 ps can be successfully obtained using the novel single-shot fourth-order auto-correlator, which is the highest dynamic range with simultaneous high time resolution for single-shot temporal contrast measurement so far. Furthermore, the temporal contrast of a PW laser system is successfully measured in single-shot with a dynamic range of about 2×10^10 and a time resolution of 160 fs.

       PDF全文 (下载：3)        Advanced Photonics ，年第卷第期 pp.      

Linnenbank Heiko   Steinle Tobias   M?rz Florian   Floess Moritz   Cui Han   Glidle Andrew   Giessen Harald  

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We present a fully automated laser system with low intensity noise for coherent Raman scattering microscopy. The robust two-color system is pumped by a solid-state oscillator, which furthermore provides the Stokes pulses fixed at 1043 nm. The tunable 750 – 950 nm pump pulses are generated by a frequency-doubled fiber-feedback femtosecond optical parametric oscillator. The resulting pulse duration of 1.2 ps provides a viable compromise between optimal coherent Raman scattering signal and the necessary spectral resolution. Thus, a spectral range of 1015 – 3695 cm^-1 with spectral resolution of less than 13 cm^-1 can be addressed.

       PDF全文 (下载：10)        Advanced Photonics ，年第卷第期 pp.      

Baranov Denis  

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N.A.

       PDF全文 (下载：1)        Advanced Photonics ，年第卷第期 pp.      

Cozzolino Daniele   Polino Emanuele   Valeri Mauro   Carvacho Gonzalo   Bacco Davide   Spagnolo Nicolò   Oxenl?we Leif   Sciarrino Fabio  

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Entanglement distribution between distant parties is one of the most important and challenging tasks in quantum communication. Distribution of photonic entangled states using optical fiber links is a fundamental building block towards quantum networks. Among the different degrees of freedom, orbital angular momentum (OAM) is one of the most promising due to its natural capability to encode high dimensional quantum states. In this article, we experimentally demonstrate fiber distribution of hybrid polarization-vector vortex entangled photon pairs. To this end, we exploit a recently developed air-core fiber which supports OAM modes. High fidelity distribution of the entangled states is demonstrated by performing quantum state tomography in the polarization-OAM Hilbert space after fiber propagation, and by violations of Bell inequalities and multipartite entanglement tests. The present results open new scenarios for quantum applications where correlated complex states can be transmitted by exploiting the vectorial nature of light.

       PDF全文 (下载：3)        Advanced Photonics ，年第卷第期 pp.      

Li Jingxi   Mengu Deniz   Luo Yi   Rivenson Yair   Ozcan Aydogan  

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Diffractive deep neural networks have been introduced earlier as an optical machine learning framework that uses task-specific diffractive surfaces designed by deep learning to all-optically perform inference, achieving promising performance for object classification and imaging. Here we demonstrate systematic improvements in diffractive neural networks based on a differential measurement technique that mitigates the strict non-negativity constraint of light intensity. In this differential detection scheme, each class is assigned to a separate pair of detectors, behind a diffractive network, and the class inference is made by maximizing the normalized signal difference between the photodetector pairs. Using class-specific differential detection in jointly-optimized diffractive neural networks that operate in parallel, our simulations achieved blind testing accuracies of 98.52%, 91.48% and 50.82% for MNIST, Fashion-MNIST and grayscale CIFAR-10 datasets, respectively, coming close to the performance of some of the earlier generations of all-electronic deep neural networks. We also independently-optimized multiple diffractive networks and utilized them in a way that is similar to ensemble methods practiced in machine learning; using 3 independently-optimized differential diffractive neural networks that optically project their light onto a common output/detector plane, we numerically achieved blind testing accuracies of 98.59%, 91.06% and 51.44% for MNIST, Fashion-MNIST and grayscale CIFAR-10 datasets, respectively.

       PDF全文 (下载：0)        Advanced Photonics ，年第卷第期 pp.      

XU Da   Han Zi-Zhao   Lu Yu-Kun   Gong Qihuang   Qiu Cheng-Wei   Chen Gang   Xiao Yunfeng  

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Synchronization is of importance in both fundamental and applied physics, but their demonstration at the micro/nanoscale is mainly limited to low-frequency oscillations like mechanical resonators. Here, we report the synchronization of two coupled optical microresonators, in which the high-frequency resonances in optical domain are aligned with reduced noise. It is found that two types of synchronization emerge with either the first- or second-order transition, both presenting a process of spontaneous symmetry breaking. In the second-order regime, the synchronization happens with an invariant topological character number and a larger detuning than that of the first-order case. Furthermore, an unconventional hysteresis behavior is revealed for a time-dependent coupling strength, breaking the static limitation and the temporal reciprocity. The synchronization of optical microresonators offers great potential in reconfigurable simulations of many-body physics and scalable photonic devices on a chip.

       PDF全文 (下载：3)        Advanced Photonics ，年第卷第期 pp.      

Narimanov Evgenii  

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We show that dielectric waveguides formed by materials with strong optical anisotropy support electromagnetic waves that combine the properties of propagating and evanescent fields. These "ghost waves" are created in tangent bifurcations that ``annihilate'' pairs of positive- and negative-index modes, and represent the optical analogue of the "ghost orbits" in the quantum theory of non-integrable dynamical systems. Ghost waves can be resonantly coupled to the incident evanescent field, which then grows exponentially through the anisotropic media -- as in the case of negative index materials. As ghost waves are supported by transparent dielectric media, the proposed approach to electromagnetic field enhancement is free from the ``curse'' of material loss that is inherent to conventional negative index composites.

       PDF全文 (下载：2)        Advanced Photonics ，年第卷第期 pp.      

Zeng Liangwei   Zeng Jianhua  

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Because of possessing a variety of fascinating and unexpected macroscopic phenomena, Bose-Einstein condensate (BEC) has attracted sustained attention in recent years---particularly for the field of solitons and associated nonlinear phenomena. Meanwhile, optical lattices have emerged as a versatile toolbox for understanding the properties and controlling the dynamics of BEC, among which an iconic result is the realization of bright gap solitons. However, the dark gap solitons are still unproven experimentally and their properties in more than one dimension remain unknown. We here survey, numerically and theoretically, the formation and stability properties of gap-type dark localized modes in the context of ultracold atoms trapped in optical lattices. Two kinds of stable dark localized modes---gap solitons and soliton clusters---are predicted in both the one- and two-dimensional geometries. The vortical counterparts of both modes are constructed as well in two dimension. A unique feature is the existence of nonlinear Bloch wave background on which all above gap modes are situated. Employing linear-stability analysis and direct simulations, stability regions of the predicted modes are obtained. Our results offer the possibility of observing dark gap localized structures with cutting-edge techniques in ultracold atoms experiments and beyond, including in optics with photonic crystals and lattices.

       PDF全文 (下载：3)        Advanced Photonics ，年第卷第期 pp.