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  • Composed multicore fiber structure for direction-sensitive curvature monitoring
    APL Photonics (IF 4.864) Pub Date : 2020-07-01
    Joel Villatoro; Josu Amorebieta; Angel Ortega-Gomez; Enrique Antonio-Lopez; Joseba Zubia; Axel Schülzgen; Rodrigo Amezcua-Correa

    The present work deals with a curvature sensor that consists of two segments of asymmetric multicore fiber (MCF) fusion spliced with standard single mode fiber (SMF). The MCF comprises three strongly coupled cores; one of such cores is at the geometrical center of the MCF. The two segments of MCF are short, have different lengths (less than 2 cm each), and are rotated 180° with respect to each other

  • Enhancing the modal purity of orbital angular momentum photons
    APL Photonics (IF 4.864) Pub Date : 2020-07-13
    Isaac Nape; Bereneice Sephton; Yao-Wei Huang; Adam Vallés; Cheng-Wei Qiu; Antonio Ambrosio; Federico Capasso; Andrew Forbes

    Orbital angular momentum (OAM) beams with topological charge ℓ are commonly generated and detected by modulating an incoming field with an azimuthal phase profile of the form exp(iℓϕ) by a variety of approaches. This results in unwanted radial modes and reduced power in the desired OAM mode. Here, we show how to enhance the modal purity in the creation and detection of classical OAM beams and in the

  • Coherent fluctuations in time-domain diffuse optics
    APL Photonics (IF 4.864) Pub Date : 2020-07-14
    Lorenzo Colombo; Saeed Samaei; Pranav Lanka; Daniele Ancora; Marco Pagliazzi; Turgut Durduran; Piotr Sawosz; Adam Liebert; Antonio Pifferi

    Near infrared light pulses, multiply scattered by random media, carry useful information regarding the sample key constituents and their microstructures. Usually, the photon diffusion equation is used to interpret the data, which neglects any interference effect in the detected light fields. However, in several experimental techniques, such as diffuse correlation spectroscopy or laser speckle flowmetry

  • Objective-free excitation of quantum emitters with a laser-written micro parabolic mirror
    APL Photonics (IF 4.864) Pub Date : 2020-07-17
    Sergii Morozov; Stefano Vezzoli; Ali Hossain Khan; Iwan Moreels; Riccardo Sapienza

    The efficient excitation of quantum sources such as quantum dots or single molecules requires high numerical aperture optics, which is often a challenge in cryogenics or in ultrafast optics. Here, we propose a 3.2 μm wide parabolic mirror, with 0.8 μm focal length, fabricated by direct laser writing on CdSe/CdS colloidal quantum dots, capable of focusing the excitation light to a sub-wavelength spot

  • Optical detection of the percolation threshold of nanoscale silver coatings with optical fiber gratings
    APL Photonics (IF 4.864) Pub Date : 2020-07-01
    Fu Liu; Xuejun Zhang; Tuan Guo; Jacques Albert

    The metal-to-dielectric transition of silver films deposited on single-mode optical fibers is monitored by measurements of the transmission spectra of tilted fiber Bragg gratings inscribed in the core of the fiber. In situ, real-time measurements of the spectrum at wavelengths near 1550 nm during the wet etching of a 50 nm thick silver coating show a sudden and temporary decrease of more than 90% in

  • Integrated vortex beam emitter in the THz frequency range: Design and simulation
    APL Photonics (IF 4.864) Pub Date : 2020-07-01
    Hailong Pi; Tasmiat Rahman; Stuart A. Boden; Tianjun Ma; Jize Yan; Xu Fang

    Compact vortex beam emitters have emerged as new light sources for novel applications in areas including spectroscopy, particle manipulation, and communications. Reported devices depend on linear optical phenomena and emit light in the near-infrared (IR) regime. Here, we propose and numerically evaluate a nonlinear vortex beam emitter that functions in the THz regime. The design utilizes a LiNbO3 microring

  • Observation of near-infrared sub-Poissonian photon emission in hexagonal boron nitride at room temperature
    APL Photonics (IF 4.864) Pub Date : 2020-07-07
    Robin Camphausen; Loris Marini; Sherif Abdulkader Tawfik; Toan Trong Tran; Michael J. Ford; Stefano Palomba

    The generation of non-classical light states in the near-infrared (NIR) is important for a number of photonic quantum technologies. Here, we report the first experimental observation of sub-Poissonian NIR (1.24 eV) light emission from defects in a 2D hexagonal boron nitride (hBN) sheet at room temperature. Photoluminescence statistics shows g(2)(0) = 0.6, which is a signature of the quantum nature

  • An entanglement-based quantum network based on symmetric dispersive optics quantum key distribution
    APL Photonics (IF 4.864) Pub Date : 2020-07-08
    Xu Liu; Xin Yao; Rong Xue; Heqing Wang; Hao Li; Zhen Wang; Lixing You; Xue Feng; Fang Liu; Kaiyu Cui; Yidong Huang; Wei Zhang

    Quantum key distribution (QKD) is a crucial technology for information security in the future. Developing simple and efficient ways to establish QKD among multiple users is important to extend the applications of QKD in communication networks. Herein, we proposed a scheme of symmetric dispersive optics QKD and demonstrated an entanglement-based quantum network based on it. In the experiment, a broadband

  • Reconstruction of angle-resolved backscattering through a multimode fiber for cell nuclei and particle size determination
    APL Photonics (IF 4.864) Pub Date : 2020-07-09
    Haoran Zhang; Zachary A. Steelman; Silvia Ceballos; Kengyeh K. Chu; Adam Wax

    We demonstrate the reconstruction of angle-resolved optical backscattering after transmission through a multimode fiber. Angle-resolved backscattering is an important tool for particle sizing, and has been developed as a diagnostic modality for detecting epithelial pre-cancer. In this work, we fully characterized the transfer function of a multimode fiber using a plane-wave illumination basis across

  • Amorphous superconducting nanowire single-photon detectors integrated with nanophotonic waveguides
    APL Photonics (IF 4.864) Pub Date : 2020-07-10
    M. Häußler; M. Yu. Mikhailov; M. A. Wolff; C. Schuck

    Future applications in integrated quantum photonics will require large numbers of efficient, fast, and low-noise single-photon counters. Superconducting nanowire single-photon detectors made from amorphous material systems are best suited to meet these demands, but the integration with nanophotonic circuits has remained a challenge. Here, we show how amorphous molybdenum silicide (MoSi) nanowires are

  • Spectroelectrochemical measurement and modulation of exciton-polaritons
    APL Photonics (IF 4.864) Pub Date : 2020-07-13
    Wonmi Ahn; Blake S. Simpkins

    Quantum emitters strongly coupled to optical cavity modes create new hybrid states called polaritons, resulting in a vacuum Rabi splitting (Ω). Strikingly, the magnitude of this splitting correlates with modified emission properties and chemical reaction rates. However, active control of this coupling strength is difficult due to the fixed properties of the coupled oscillators (both the quantum emitter

  • Resonant modes of reflecting gratings engineered for multimodal sensing
    APL Photonics (IF 4.864) Pub Date : 2020-07-14
    Mohammad Abutoama; Aabha Bajaj; Dong Li; Yawen Wang; Lin Jiang; Ibrahim Abdulhalim

    Reflecting gratings with narrow grooves exhibit multiple electromagnetic modes. Using a simple setup, surface plasmon (SP), cavity mode (CM) resonance shift, surface-enhanced fluorescence (SEF), and surface-enhanced Raman scattering signals can be measured, thus forming a multimodal sensing or imaging system. The nature of these modes is first analyzed using dispersion curves as a function of the wavelength

  • Designer Bloch plasmon polariton dispersion in grating-coupled hyperbolic metamaterials
    APL Photonics (IF 4.864) Pub Date : 2020-07-20
    Nicolò Maccaferri; Tommi Isoniemi; Michael Hinczewski; Marzia Iarossi; Giuseppe Strangi; Francesco De Angelis

    Hyperbolic metamaterials (HMMs) are anisotropic optical materials supporting highly confined propagating electromagnetic modes. However, it is challenging to tailor and excite these modes at optical frequencies by prism coupling because of the unavailability of high refractive index prisms for matching the momentum between the incident light and the guided modes. Here, we report on the mechanism of

  • High efficiency four wave mixing and optical bistability in amorphous silicon carbide ring resonators
    APL Photonics (IF 4.864) Pub Date : 2020-07-21
    Peng Xing; Danhao Ma; Lionel C. Kimerling; Anuradha M. Agarwal; Dawn T. H. Tan

    We demonstrate high efficiency wavelength conversion via four wave mixing in amorphous silicon carbide ring resonators with a loaded quality factor of 70 000. Owing to the high quality factor and high nonlinearity of amorphous silicon carbide, −21 dB conversion efficiency is achieved with 15 mW pump power. Moreover, the thermo-optic coefficient (TOC) of amorphous silicon carbide is measured to be 1

  • Frequency-modulated diode laser frequency combs at 2μm wavelength
    APL Photonics (IF 4.864) Pub Date : 2020-07-21
    Lukasz A. Sterczewski; Clifford Frez; Siamak Forouhar; David Burghoff; Mahmood Bagheri

    Chip-scale electrically pumped optical frequency combs (OFCs) are expected to play a fundamental role in applications ranging from telecommunications to optical sensing. To date, however, the availability of such sources around 2 μm has been scarce. Here, we present a frequency-modulated OFC operating around 2060 nm of wavelength exploiting the inherent gain nonlinearity of single-section GaSb-based

  • Highly sensitive magnetic field microsensor based on direct laser writing of fiber-tip optofluidic Fabry–Pérot cavity
    APL Photonics (IF 4.864) Pub Date : 2020-07-24
    Dengwei Zhang; Heming Wei; Huizhu Hu; Sridhar Krishnaswamy

    In this paper, a polymer micro-Fabry–Pérot interferometer (FPI) fabricated via direct laser writing using two-photon polymerization techniques on a single mode fiber tip is proposed, designed, simulated, and experimentally demonstrated as a magnetic field probe. The sensor comprises a tapered waveguide with a length of 100 µm and a diameter of 1 µm along the axis connecting the two reflecting surfaces

  • Optical time-frequency transfer across a free-space, three-node network
    APL Photonics (IF 4.864) Pub Date : 2020-07-29
    Martha I. Bodine; Jennifer L. Ellis; William C. Swann; Sarah A. Stevenson; Jean-Daniel Deschênes; Emily D. Hannah; Paritosh Manurkar; Nathan R. Newbury; Laura C. Sinclair

    We demonstrate frequency-comb-based optical two-way time-frequency transfer across a three-node clock network. A fielded, bidirectional relay node connects laboratory-based master and end nodes, allowing the network to span 28 km of turbulent outdoor air while keeping optical transmit powers below 5 mW. Despite the comparatively high instability of the free-running local oscillator at the relay node

  • Photonic glass based structural color
    APL Photonics (IF 4.864) Pub Date : 2020-06-08
    Guoliang Shang; Manfred Eich; Alexander Petrov

    Structural coloration, which is based on spectrally selective scattering from optical structures, has recently attracted wide attention as a replacement of pigment colors based on the selective light absorption in chemical structures. Structural colors can be produced from transparent non-toxic materials and provide high stability under solar radiation. To provide angle independent non-iridescent colors

  • Super-resolution localization microscopy: Toward high throughput, high quality, and low cost
    APL Photonics (IF 4.864) Pub Date : 2020-06-24
    Hongqiang Ma; Yang Liu

    After nearly 15 years since its initial debut, super-resolution localization microscopy that surpasses the diffraction-limited resolution barrier of optical microscopy has rapidly gotten out of the ivory tower and entered a new phase to address various challenging biomedical questions. Recent advances in this technology greatly increased the imaging throughput, improved the imaging quality, simplified

  • Injection-seeded backward terahertz-wave parametric oscillator
    APL Photonics (IF 4.864) Pub Date : 2020-06-01
    Yuma Takida; Kouji Nawata; Hiroaki Minamide

    Engineered quasi-phase-matching in a periodically poled nonlinear crystal has enabled backward optical parametric oscillators, where a pump photon is down-converted to counterpropagating signal and idler photons without an optical cavity. Here, we demonstrate an injection-seeded backward terahertz-wave parametric oscillator (BW-TPO) based on a slant-strip-type periodically poled lithium niobate crystal

  • Fluorescence polarization filtering for accurate single molecule localization
    APL Photonics (IF 4.864) Pub Date : 2020-06-05
    Oleksii Nevskyi; Roman Tsukanov; Ingo Gregor; Narain Karedla; Jörg Enderlein

    Single-Molecule Localization Microscopy (SMLM) has become one of the most important methods of super-resolution fluorescence microscopy. It is based on the precise localization of single molecules in wide-field microscopy images. It is well known that the localization accuracy can show a significant bias if the imaged molecules have a fixed orientation and are located either close to an interface or

  • Observing mode-dependent wavelength-to-time mapping in few-mode fibers using a single-photon detector array
    APL Photonics (IF 4.864) Pub Date : 2020-06-09
    Harikumar K. Chandrasekharan; Katjana Ehrlich; Michael G. Tanner; Dionne M. Haynes; Sebabrata Mukherjee; Tim A. Birks; Robert R. Thomson

    Wavelength-to-time mapping (WTM)—stretching ultrashort optical pulses in a dispersive medium such that the instantaneous frequency becomes time-dependent—is usually performed using a single-mode fiber. In a number of applications, such as time-stretch imaging (TSI), the use of this single-mode fiber during WTM limits the achievable sampling rate and the imaging quality. Multimode fiber based WTM is

  • Cavity mode manipulated by single gold nanoparticles
    APL Photonics (IF 4.864) Pub Date : 2020-06-09
    Yipeng Lun; Ziyu Zhan; Fuxing Gu; Pan Wang; Huakang Yu; Zhi-yuan Li

    The ability to manipulate microlaser performance is highly desirable so as to promote on-chip classical and quantum information-processing technology. Here, we demonstrate that mode manipulation of bottle microresonators is enabled by precise deposition of single gold nanoparticles in a reconfigurable and selective manner. Numerical investigation reveals the mechanism of introducing optical loss via

  • Removing non-resonant background from CARS spectra via deep learning
    APL Photonics (IF 4.864) Pub Date : 2020-06-25
    C. M. Valensise; A. Giuseppi; F. Vernuccio; A. De la Cadena; G. Cerullo; D. Polli

    Broadband Coherent Anti-Stokes Raman Scattering (B-CARS) is a powerful label-free nonlinear spectroscopy technique allowing one to measure the full vibrational spectrum of molecules and solids. B-CARS spectra, however, suffer from the presence of a spurious signal, called non-resonant background (NRB), which interferes with the resonant vibrational one, distorting the line shapes and degrading the

  • High-Qnanobeam cavities on a silicon nitride platform enabled by slow light
    APL Photonics (IF 4.864) Pub Date : 2020-06-02
    Jiahao Zhan; Zeinab Jafari; Sylvain Veilleux; Mario Dagenais; Israel De Leon

    Silicon nitride integrated photonic devices benefit from a wide working spectral range covering the visible and near-infrared spectra, which in turn enables important applications in bio-photonics, optical communications, and sensing. High-quality factor optical resonators are essential photonic devices for such applications. However, implementing such resonators on a silicon nitride platform is quite

  • Asymmetric dual-grating gates graphene FET for detection of terahertz radiations
    APL Photonics (IF 4.864) Pub Date : 2020-06-09
    J. A. Delgado-Notario; V. Clericò; E. Diez; J. E. Velázquez-Pérez; T. Taniguchi; K. Watanabe; T. Otsuji; Y. M. Meziani

    A graphene-based field-effect-transistor with asymmetric dual-grating gates was fabricated and characterized under excitation of terahertz radiation at two frequencies: 0.15 THz and 0.3 THz. The graphene sheet was encapsulated between two flakes of h-BN and placed on a highly doped SiO2/Si substrate. An asymmetric dual-grating gate was implemented on the h-BN top flake. Even though no antenna was used

  • Tunable third harmonic generation in the vacuum ultraviolet region using dielectric nanomembranes
    APL Photonics (IF 4.864) Pub Date : 2020-06-12
    Kuniaki Konishi; Daisuke Akai; Yoshio Mita; Makoto Ishida; Junji Yumoto; Makoto Kuwata-Gonokami

    Tunable coherent light sources operating in the vacuum ultraviolet (VUV) region in the 100–200-nm (6–12 eV) wavelength range have important spectroscopic applications in many research fields, including time-resolved angle-resolved photoemission spectroscopy. Recent advances in laser technology have enabled the upconversion of visible femtosecond lasers to the vacuum and extreme ultraviolet regions

  • Photoinjection of fluorescent nanoparticles into intact plant cells using femtosecond laser amplifier
    APL Photonics (IF 4.864) Pub Date : 2020-06-15
    Taufiq Indra Rukmana; Gabriela Moran; Rachel Méallet-Renault; Gilles Clavier; Tadashi Kunieda; Misato Ohtani; Taku Demura; Ryohei Yasukuni; Yoichiroh Hosokawa

    The introduction of nanoparticles to intact plant cells is promising as a transporting technique of a wide range of functional molecules. Among various molecular delivery methods, femtosecond laser photoinjection possesses target selectivity at a single cell level and is potentially applicable for many types of materials. However, for plant cells, the vacuoles’ turgor pressure and the thick cell wall

  • Sub-megahertz narrow-band photon pairs at 606 nm for solid-state quantum memories
    APL Photonics (IF 4.864) Pub Date : 2020-06-15
    Jianji Liu; Jiachen Liu; Ping Yu; Guoquan Zhang

    We report on the development of a source of ultra-narrow-band photon pairs using the cavity-enhanced spontaneous parametric down conversion. The photon-pair source has a bandwidth of 265 ± 15 kHz at 606 nm and a spectral brightness of 216 ± 5 pairs/(s · mW · MHz) per longitudinal mode, which could be suitable for Pr3+ ion-based solid-state quantum memories.

  • Diffraction-induced enhancement of optical spin Hall effect in a dielectric grating
    APL Photonics (IF 4.864) Pub Date : 2020-06-18
    Minkyung Kim; Dasol Lee; Byoungsu Ko; Junsuk Rho

    The enhancement of the optical spin Hall effect (OSHE) of a transmitted beam has been achieved in a small incident angle of a sub-degree scale. The OSHE at a large incident angle can be beneficial in optical applications, such as polarization-dependent sensors and filters, but studies to increase the OSHE at a large incident angle have been elusive in transmission mode. We propose a dielectric grating

  • Far-field unlabeled super-resolution imaging with superoscillatory illumination
    APL Photonics (IF 4.864) Pub Date : 2020-06-19
    Edward T. F. Rogers; Shmma Quraishe; Katrine S. Rogers; Tracey A. Newman; Peter J. S. Smith; Nikolay I. Zheludev

    Unlabeled super-resolution is the next grand challenge in imaging. Stimulated emission depletion and single-molecule microscopies have revolutionized the life sciences but are still limited by the need for reporters (labels) embedded within the sample. While the Veselago–Pendry “super-lens,” using a negative-index metamaterial, is a promising idea for imaging beyond the diffraction limit, there are

  • Optical parametric gain in CMOS-compatible sub-100μm photonic crystal waveguides
    APL Photonics (IF 4.864) Pub Date : 2020-06-22
    Ezgi Sahin; Doris K. T. Ng; Dawn T. H. Tan

    Emerging compositionally engineered complementary metal-oxide-semiconductor (CMOS)-compatible platforms have been employed for high efficiencies in various on-chip applications, including optical parametric amplification and wavelength conversion. Combining the novel nonlinear optics platforms such as ultra-silicon-rich nitride (USRN: Si7N3) with periodic waveguide structures can lead to further enhancement

  • Mode-field switching of nanolasers
    APL Photonics (IF 4.864) Pub Date : 2020-06-24
    Daniele Pellegrino; Pierre Busi; Francesco Pagliano; Bruno Romeira; Frank W. van Otten; Andrei Yu. Silov; Andrea Fiore

    Due to their small sizes and low threshold, nanolasers play a pivotal role in the field of low-energy scalable photonic technologies. High-speed modulation of nanolasers is needed for their application in data communication, but its implementation has been hampered by the small scales involved, leading to large electrical parasitics. Here we experimentally demonstrate the proof-of-principle of a novel

  • Optical multi-stability in a nonlinear high-order microring resonator filter
    APL Photonics (IF 4.864) Pub Date : 2020-05-22
    Li Jin, Luigi Di Lauro, Alessia Pasquazi, Marco Peccianti, David J. Moss, Roberto Morandotti, Brent E. Little, Sai Tak Chu

    We theoretically analyze and experimentally demonstrate optical bi-stability and multi-stability in an integrated nonlinear high-order microring resonator filter based on high-index contrast doped silica glass. We use a nonlinear model accounting for both the Kerr and thermal effects to analyze the instability behavior of the coupled-resonator based filter. The model also accurately predicts the multi-stable

  • Controlling dispersion in multifunctional metasurfaces
    APL Photonics (IF 4.864) Pub Date : 2020-05-22
    Jared Sisler, Wei Ting Chen, Alexander Y. Zhu, Federico Capasso

    Metasurfaces can be designed to exhibit different functionalities with incident wavelength, polarization, or angles through appropriate choice and design of the constituent nanostructures. As a proof-of-concept, we design and simulate three multifunctional metalenses with vastly different focal lengths at blue and red wavelengths to show that the wavelength dependence of focal length shift can be engineered

  • 26.8-m THz wireless transmission of probabilistic shaping 16-QAM-OFDM signals
    APL Photonics (IF 4.864) Pub Date : 2020-05-20
    Shiwei Wang, Zijie Lu, Wei Li, Shi Jia, Lu Zhang, Mengyao Qiao, Xiaodan Pang, Nazar Idrees, Muhammad Saqlain, Xiang Gao, Xiaoxiao Cao, Changxing Lin, Qiuyu Wu, Xianmin Zhang, Xianbin Yu

    Recently, remarkable efforts have been made in developing wireless communication systems at ultrahigh data rates, with radio frequency (RF) carriers in the millimeter wave (30–300 GHz) and/or in the terahertz (THz, >300 GHz) bands. Converged technologies combining both the electronics and the photonics show great potential to provide feasible solutions with superior performance compared to conventional

  • Nonlinear depolarization of light in optical communication fiber
    APL Photonics (IF 4.864) Pub Date : 2020-05-18
    Lothar Moeller

    We report the experimental observation of a novel transmission phenomenon in optical long-haul communication systems. Unpolarized ASE depolarizes via nonlinear fiber interactions a cw laser light during their copropagation which leads to small but measurable ultrafast polarization state fluctuations at the fiber output. We provide a phenomenological approach and a theory that qualitatively corroborates

  • Objective and efficient terahertz signal denoising by transfer function reconstruction
    APL Photonics (IF 4.864) Pub Date : 2020-05-12
    Xuequan Chen, Qiushuo Sun, Rayko I. Stantchev, Emma Pickwell-MacPherson

    As an essential processing step in many disciplines, signal denoising efficiently improves data quality without extra cost. However, it is relatively under-utilized for terahertz spectroscopy. The major technique reported uses wavelet denoising in the time-domain, which has a fuzzy physical meaning and limited performance in low-frequency and water-vapor regions. Here, we work from a new perspective

  • High-resolution sub-sampling incoherent x-ray imaging with a single-pixel detector
    APL Photonics (IF 4.864) Pub Date : 2020-05-04
    Yu-Hang He, Ai-Xin Zhang, Ming-Fei Li, Yi-Yi Huang, Bao-Gang Quan, Da-Zhang Li, Ling-An Wu, Li-Ming Chen

    X-ray “ghost” imaging has drawn great attention for its potential to obtain images with a high resolution and lower radiation dose in medical diagnosis, even with only a single-pixel detector. However, it is hard to realize with a portable x-ray source due to its low flux. Here, we demonstrate a computational x-ray ghost imaging scheme where a real bucket detector and specially designed high-efficiency

  • Anisotropic diffusion inCyphochiluswhite beetle scales
    APL Photonics (IF 4.864) Pub Date : 2020-05-04
    Seung Ho Lee, Sang M. Han, Sang Eon Han

    Cyphochilus white beetles possess an exceptional ability to scatter visible light from their scales, which have anisotropic nanofibrillar network structures. We discover a striking effect that diffusely incident light on the beetle scales is preferentially channeled sideways and scattered backward on the average after traversing a vertical distance corresponding to only two scattering events. For normally

  • Low-loss, high-bandwidth fiber-to-chip coupling using capped adiabatic tapered fibers
    APL Photonics (IF 4.864) Pub Date : 2020-05-01
    Saeed Khan, Sonia M. Buckley, Jeff Chiles, Richard P. Mirin, Sae Woo Nam, Jeffrey M. Shainline

    We demonstrate adiabatically tapered fibers terminating in sub-micron tips that are clad with a higher-index material for coupling to an on-chip waveguide. This cladding enables coupling to a high-index waveguide without losing light to the buried oxide. A technique to clad the tip of the tapered fiber with a higher-index polymer is introduced. Conventional tapered waveguides and forked tapered waveguide

  • Label-free colorectal cancer screening using deep learning and spatial light interference microscopy (SLIM)
    APL Photonics (IF 4.864) Pub Date : 2020-04-28
    Jingfang K. Zhang, Yuchen R. He, Nahil Sobh, Gabriel Popescu

    Current pathology workflow involves staining of thin tissue slices, which otherwise would be transparent, followed by manual investigation under the microscope by a trained pathologist. While the hematoxylin and eosin (H&E) stain is well-established and a cost-effective method for visualizing histology slides, its color variability across preparations and subjectivity across clinicians remain unaddressed

  • Deep learning for video compressive sensing
    APL Photonics (IF 4.864) Pub Date : 2020-03-06
    Mu Qiao, Ziyi Meng, Jiawei Ma, Xin Yuan

    We investigate deep learning for video compressive sensing within the scope of snapshot compressive imaging (SCI). In video SCI, multiple high-speed frames are modulated by different coding patterns and then a low-speed detector captures the integration of these modulated frames. In this manner, each captured measurement frame incorporates the information of all the coded frames, and reconstruction

  • Computational de-noising based on deep learning for phase data in digital holographic interferometry
    APL Photonics (IF 4.864) Pub Date : 2020-03-19
    Silvio Montresor, Marie Tahon, Antoine Laurent, Pascal Picart

    This paper presents a deep-learning-based algorithm dedicated to the processing of speckle noise in phase measurements in digital holographic interferometry. The deep learning architecture is trained with phase fringe patterns including faithful speckle noise, having non-Gaussian statistics and non-stationary property, and exhibiting spatial correlation length. The performances of the speckle de-noiser

  • Multichannel fiber laser acoustic emission sensor system for crack detection and location in accelerated fatigue testing of aluminum panels
    APL Photonics (IF 4.864) Pub Date : 2020-03-20
    Caitlin R. S. Williams, Meredith N. Hutchinson, Joseph D. Hart, Marriner H. Merrill, Peter Finkel, William R. PogueIII, Geoffrey A. Cranch

    Detection and location of the source of acoustic emission in a thin aluminum panel is demonstrated using a multichannel fiber laser sensor system. Acoustic emission generated by a crack in an aluminum panel used as a test coupon in an accelerated fatigue experiment is detected and the location of the crack identified. Acoustic emission is detected over a bandwidth of around 0.5 MHz from a serially

  • Controlling spatiotemporal nonlinearities in multimode fibers with deep neural networks
    APL Photonics (IF 4.864) Pub Date : 2020-03-24
    U. Teğin, B. Rahmani, E. Kakkava, N. Borhani, C. Moser, D. Psaltis

    Spatiotemporal nonlinear interactions in multimode fibers are of interest for beam shaping and frequency conversion by exploiting the nonlinear interaction of different pump modes from quasi-continuous wave to ultrashort pulses centered around visible to infrared pump wavelengths. The nonlinear effects in multi-mode fibers depend strongly on the excitation condition; however, relatively little work

  • Synthetic photonic lattice for single-shot reconstruction of frequency combs
    APL Photonics (IF 4.864) Pub Date : 2020-03-31
    James G. Titchener, Bryn Bell, Kai Wang, Alexander S. Solntsev, Benjamin J. Eggleton, Andrey A. Sukhorukov

    We formulate theoretically and demonstrate experimentally an all-optical method for reconstruction of the amplitude, phase, and coherence of frequency combs from a single-shot measurement of the spectral intensity. Our approach exploits synthetic frequency lattices with pump-induced spectral short- and long-range couplings between different signal components across a broad bandwidth of hundreds of

  • Distributed acoustic sensing for seismic activity monitoring
    APL Photonics (IF 4.864) Pub Date : 2020-03-24
    María R. Fernández-Ruiz, Marcelo A. Soto, Ethan F. Williams, Sonia Martin-Lopez, Zhongwen Zhan, Miguel Gonzalez-Herraez, Hugo F. Martins

    Continuous, real-time monitoring of surface seismic activity around the globe is of great interest for acquiring new insight into global tomography analyses and for recognition of seismic patterns leading to potentially hazardous situations. The already-existing telecommunication fiber optic network arises as an ideal solution for this application, owing to its ubiquity and the capacity of optical

  • Diamond Brillouin laser in the visible
    APL Photonics (IF 4.864) Pub Date : 2020-03-03
    Zhenxu Bai, Robert J. Williams, Ondrej Kitzler, Soumya Sarang, David J. Spence, Yulei Wang, Zhiwei Lu, Richard P. Mildren

    Brillouin lasers providing extremely narrow-linewidth are emerging as a powerful tool for microwave photonics, coherent communications, quantum processors, and spectroscopy. So far, laser performance and applications have been investigated for a handful of select materials and using guided-wave structures such as micro-resonators, optical fibers, and chip-based waveguides. Here, we report a Brillouin

  • Frequency scanned phase sensitive optical time-domain reflectometry interrogation in multimode optical fibers
    APL Photonics (IF 4.864) Pub Date : 2020-03-16
    K. Markiewicz, J. Kaczorowski, Z. Yang, L. Szostkiewicz, A. Dominguez-Lopez, K. Wilczynski, M. Napierala, T. Nasilowski, L. Thévenaz

    Standard multimode optical fibers normally support transmission over some 100 modes. Large differences in the propagation constant and the spatial distribution of distinct modes degrade the performance of phase-sensitive optical time-domain reflectometry measurements. In this work, we present a new realization of a coherent time-domain interrogation technique using single-mode operation in multimode

  • Unveiling quantum-limited operation of interband cascade lasers
    APL Photonics (IF 4.864) Pub Date : 2020-03-02
    Simone Borri, Mario Siciliani de Cumis, Silvia Viciani, Francesco D’Amato, Paolo De Natale

    A comprehensive experimental analysis of the frequency fluctuations of a mid-infrared interband cascade laser, down to the quantum-limited operation, is reported. These lasers differ from any other class of semiconductor lasers in their structure and internal carrier generation and transport processes. Although already commercially available, a full evaluation of their potential has not been possible

  • One-dimensional, surface emitting, disordered Terahertz lasers
    APL Photonics (IF 4.864) Pub Date : 2020-03-03
    Luca Salemi, Katia Garrasi, Simone Biasco, Teresa Crisci, Harvey E. Beere, David A. Ritchie, Miriam S. Vitiello

    Quantum cascade lasers are, by far, the most compact, powerful, and spectrally pure sources of radiation at terahertz frequencies, and, as such, they are of crucial importance for applications in metrology, spectroscopy, imaging, and astronomy, among many others. However, for many of those applications, particularly imaging, tomography, and near-field microscopy, undesired artifacts, resulting from

  • Wavefront shaping in multimode fibers by transmission matrix engineering
    APL Photonics (IF 4.864) Pub Date : 2020-03-13
    Shachar Resisi, Yehonatan Viernik, Sebastien M. Popoff, Yaron Bromberg

    We present a new approach for shaping light at the output of a multimode fiber by modulating the transmission matrix of the system rather than the incident light. We apply computer-controlled mechanical perturbations to the fiber and obtain a desired intensity pattern at its output resulting from the changes to its transmission matrix. Using an all-fiber apparatus, we demonstrate focusing light at

  • Continuous-wave 6-dB-squeezed light with 2.5-THz-bandwidth from single-mode PPLN waveguide
    APL Photonics (IF 4.864) Pub Date : 2020-03-30
    Takahiro Kashiwazaki, Naoto Takanashi, Taichi Yamashima, Takushi Kazama, Koji Enbutsu, Ryoichi Kasahara, Takeshi Umeki, Akira Furusawa

    Terahertz (THz)-bandwidth continuous-wave (CW) squeezed light is essential for integrating quantum processors with time-domain multiplexing (TDM) by using optical delay line interferometers. Here, we utilize a single-pass optical parametric amplifier (OPA) based on a single-spatial-mode periodically poled ZnO:LiNbO3 waveguide, which is directly bonded onto a LiTaO3 substrate. The single-pass OPA allows

  • Wavelength-independent optical fully differential operation based on the spin–orbit interaction of light
    APL Photonics (IF 4.864) Pub Date : 2020-03-30
    Shanshan He, Junxiao Zhou, Shizhen Chen, Weixing Shu, Hailu Luo, Shuangchun Wen

    Optical technology may provide important architectures for future computing, such as analog optical computing and image processing. Compared with traditional electric operation, optical operation has shown some unique advantages including faster operating speeds and lower power consumption. Here, we propose an optical full differentiator based on the spin–orbit interaction of light at a simple optical

  • Surface-passivated high-QGaAs photonic crystal nanocavity with quantum dots
    APL Photonics (IF 4.864) Pub Date : 2020-04-23
    Kazuhiro Kuruma, Yasutomo Ota, Masahiro Kakuda, Satoshi Iwamoto, Yasuhiko Arakawa

    Photonic crystal (PhC) nanocavities with high quality (Q) factors have attracted much attention because of their strong spatial and temporal light confinement capability. The resulting enhanced light–matter interactions are beneficial for diverse photonic applications, ranging from on-chip optical communications to sensing. However, currently achievable Q factors for active PhC nanocavities, which

  • InAs-based quantum cascade lasers grown on on-axis (001) silicon substrate
    APL Photonics (IF 4.864) Pub Date : 2020-04-14
    Z. Loghmari, J.-B. Rodriguez, A. N. Baranov, M. Rio-Calvo, L. Cerutti, A. Meguekam, M. Bahriz, R. Teissier, E. Tournié

    We present InAs/AlSb quantum cascade lasers (QCLs) monolithically integrated on an on-axis (001) Si substrate. The lasers emit near 8 μm with threshold current densities of 0.92–0.95 kA/cm2 at 300 K for 3.6-mm-long devices and operate in pulsed mode up to 410 K. QCLs of the same design grown for comparison on a native InAs substrate demonstrated a threshold current density of 0.75 kA/cm2 and the same

  • A single sensor based multispectral imaging camera using a narrow spectral band color mosaic integrated on the monochrome CMOS image sensor
    APL Photonics (IF 4.864) Pub Date : 2020-04-14
    Xin He, Yajing Liu, Kumar Ganesan, Arman Ahnood, Paul Beckett, Fatima Eftekhari, Dan Smith, Md Hemayet Uddin, Efstratios Skafidas, Ampalavanapillai Nirmalathas, Ranjith Rajasekharan Unnithan

    A multispectral image camera captures image data within specific wavelength ranges in narrow wavelength bands across the electromagnetic spectrum. Images from a multispectral camera can extract a additional information that the human eye or a normal camera fails to capture and thus may have important applications in precision agriculture, forestry, medicine, and object identification. Conventional

  • Deep-learning-enabled geometric constraints and phase unwrapping for single-shot absolute 3D shape measurement
    APL Photonics (IF 4.864) Pub Date : 2020-04-14
    Jiaming Qian, Shijie Feng, Tianyang Tao, Yan Hu, Yixuan Li, Qian Chen, Chao Zuo

    Fringe projection profilometry (FPP) has become a more prevalently adopted technique in intelligent manufacturing, defect detection, and some other important applications. In FPP, efficiently recovering the absolute phase has always been a great challenge. The stereo phase unwrapping (SPU) technologies based on geometric constraints can eliminate phase ambiguity without projecting any additional patterns

  • Virtual optofluidic time-stretch quantitative phase imaging
    APL Photonics (IF 4.864) Pub Date : 2020-04-13
    Haochen Yan, Yunzhao Wu, Yuqi Zhou, Muzhen Xu, Petra Paiè, Cheng Lei, Sheng Yan, Keisuke Goda

    Optofluidic time-stretch quantitative phase imaging (OTS-QPI) is a potent tool for biomedical applications as it enables high-throughput QPI of numerous cells for large-scale single-cell analysis in a label-free manner. However, there are a few critical limitations that hinder OTS-QPI from being widely applied to diverse applications, such as its costly instrumentation and inherent phase-unwrapping

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