Advanced Photonics

2020, 2(6) Column


Advanced Photonics 第2卷 第6期

Author Affiliations
Nanjing University, College of Engineering and Applied Sciences, Nanjing, China
The flat endface of an optical fiber tip is an emerging light-coupled microscopic platform that combines fiber optics with planar micro- and nanotechnologies. Since different materials and structures are integrated onto the endfaces, optical fiber tip devices have miniature sizes, diverse integrated functions, and low insertion losses, making them suitable for all-optical networks. In recent decades, the increasing demand for multifunctional optical fibers has created opportunities to develop various structures on fiber tips. Meanwhile, the unconventional shape of optical fibers presents challenges involving the adaptation of standard planar micro- and nanostructure preparation strategies for fiber tips. In this context, researchers are committed to exploring and optimizing fiber tip manufacturing techniques, thereby paving the way for future integrated all-fiber devices with multifunctional applications. First, we present a broad overview of current fabrication technologies, classified as “top-down,” “bottom-up,” and “material transfer” methods, for patterning optical fiber tips. Next, we review typical structures integrated on fiber tips and their known and potential applications, categorized with respect to functional structure configurations, including “optical functionalization” and “electrical integration.” Finally, we discuss the prospects for future opportunities involving multifunctional integrated fiber tips.
optical fibers fiber tips optical devices nanotechnology micro-optics nano-optics 
Advanced Photonics
2020, 2(6): 064001
Author Affiliations
1 East China Normal University, State Key Laboratory of Precision Spectroscopy, Shanghai, China
2 Chongqing Institute of East China Normal University, Chongqing, China
3 Jinan Institute of Quantum Technology, Jinan, China
Laser-induced breakdown spectroscopy (LIBS) is a useful tool for determination of elements in solids, liquids, and gases. For nanosecond LIBS (ns-LIBS), the plasma shielding effect limits its reproducibility, repeatability, and signal-to-noise ratios. Although femtosecond laser filament induced breakdown spectroscopy (FIBS) has no plasma shielding effects, the power density clamping inside the filaments limits the measurement sensitivity. We propose and demonstrate plasma-grating-induced breakdown spectroscopy (GIBS). The technique relies on a plasma excitation source—a plasma grating generated by the interference of two noncollinear femtosecond filaments. We demonstrate that GIBS can overcome the limitations of standard techniques such as ns-LIBS and FIBS. Signal intensity enhancement with GIBS is observed to be greater than 3 times that of FIBS. The matrix effect is also significantly reduced with GIBS, by virtue of the high power and electron density of the plasma grating, demonstrating great potential for analyzing samples with complex matrix.
femtosecond filament plasma grating induced breakdown spectroscopy high power and electron density enhancement matrix effect 
Advanced Photonics
2020, 2(6): 065001
Author Affiliations
1 The Chinese University of Hong Kong, Department of Biomedical Engineering, Hong Kong, China
2 Massachusetts Institute of Technology, Department of Mechanical Engineering, Cambridge, Massachusetts, United States
3 Massachusetts Institute of Technology, Computer Science and Artificial Intelligence Laboratory, Cambridge, Massachusetts, United States
4 Zhejiang University, College of Information Science and Electronic Engineering, Hangzhou, China
5 Massachusetts Institute of Technology, Department of Materials Science and Engineering, Cambridge, Massachusetts, United States
6 Massachusetts Institute of Technology, Laser Biomedical Research Center, Cambridge, Massachusetts, United States
7 Massachusetts Institute of Technology, Department of Biological Engineering, Cambridge, Massachusetts, United States
8 The Chinese University of Hong Kong, Shun Hing Institute of Advanced Engineering, Hong Kong, China
A new optical microscopy technique, termed high spatial and temporal resolution synthetic aperture phase microscopy (HISTR-SAPM), is proposed to improve the lateral resolution of wide-field coherent imaging. Under plane wave illumination, the resolution is increased by twofold to around 260 nm, while achieving millisecond-level temporal resolution. In HISTR-SAPM, digital micromirror devices are used to actively change the sample illumination beam angle at high speed with high stability. An off-axis interferometer is used to measure the sample scattered complex fields, which are then processed to reconstruct high-resolution phase images. Using HISTR-SAPM, we are able to map the height profiles of subwavelength photonic structures and resolve the period structures that have 198 nm linewidth and 132 nm gap (i.e., a full pitch of 330 nm). As the reconstruction averages out laser speckle noise while maintaining high temporal resolution, HISTR-SAPM further enables imaging and quantification of nanoscale dynamics of live cells, such as red blood cell membrane fluctuations and subcellular structure dynamics within nucleated cells. We envision that HISTR-SAPM will broadly benefit research in material science and biology.
quantitative phase microscopy label-free imaging material inspection cell dynamics observation 
Advanced Photonics
2020, 2(6): 065002
Author Affiliations
1 LTCI, Télécom Paris, Institut Polytechnique de Paris, Palaiseau, France
2 mirSense, Centre d’Intégration NanoInnov, Palaiseau, France
3 University of California Los Angeles, Fang Lu Mesoscopic Optics and Quantum Electronics Laboratory, Los Angeles, California, United States
4 Southwest University, College of Electronic and Information Engineering, Chongqing, China
5 Technische Universität Darmstadt, Darmstadt, Germany
6 University of New Mexico, Center for High Technology Materials, Albuquerque, New Mexico, United States
We demonstrate experimentally that mid-infrared quantum cascade lasers (QCLs) operating under external optical feedback exhibit extreme pulses. These events can be triggered by adding small amplitude periodic modulation, with the highest success rate for the case of a pulse-up excitation. These findings broaden the potential applications for QCLs, which have already been proven to be a semiconductor laser of interest for spectroscopic applications and countermeasure systems. The ability to trigger extreme events paves the way for optical neuron-like systems where information propagates as a result of high intensity bursts.
extreme pulses quantum cascade lasers nonlinear dynamics mid-infrared photonics 
Advanced Photonics
2020, 2(6): 066001
Author Affiliations
1 Nanyang Technological University, School of Electrical and Electronic Engineering, Singapore
3 Nanyang Technological University, School of Chemical and Biomedical Engineering, Singapore
Optical barcodes have demonstrated a great potential in multiplexed bioassays and cell tracking for their distinctive spectral fingerprints. The vast majority of optical barcodes were designed to identify a specific target by fluorescence emission spectra, without being able to characterize dynamic changes in response to analytes through time. To overcome these limitations, the concept of the bioresponsive dynamic photonic barcode was proposed by exploiting interfacial energy transfer between a microdroplet cavity and binding molecules. Whispering-gallery modes resulting from cavity-enhanced energy transfer were therefore converted into photonic barcodes to identify binding activities, in which more than trillions of distinctive barcodes could be generated by a single droplet. Dynamic spectral barcoding was achieved by a significant improvement in terms of signal-to-noise ratio upon binding to target molecules. Theoretical studies and experiments were conducted to elucidate the effect of different cavity sizes and analyte concentrations. Time-resolved fluorescence lifetime was implemented to investigate the role of radiative and non-radiative energy transfer. Finally, microdroplet photonic barcodes were employed in biodetection to exhibit great potential in fulfilling biomedical applications.
whispering-gallery modes optical barcodes fluorescence resonance energy transfer molecular sensing biointerface cavity-enhancement 
Advanced Photonics
2020, 2(6): 066002
Author Affiliations
1 Beihang University, Fert Beijing Institute, Advanced Innovation Center for Big Data and Brain Computing, School of Microelectronics, Beijing, China
2 Beihang University, School of Electronic and Information Engineering, Beijing, China
3 Chinese Academy of Sciences, Institute of Physics, Beijing National Laboratory for Condensed Matter Physics, Beijing, China
4 University of Chinese Academy of Sciences, School of Physical Sciences, Beijing, China
5 Beihang University, Beihang-Goertek Joint Microelectronics Institute, Qingdao Research Institute, Qingdao, China
6 Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, China
Arbitrary manipulation of broadband terahertz waves with flexible polarization shaping at the source has great potential in expanding numerous applications, such as imaging, information encryption, and all-optical coherent control of terahertz nonlinear phenomena. Topological insulators featuring unique spin-momentum–locked surface state have already exhibited very promising prospects in terahertz emission, detection, and modulation, which may lay a foundation for future on-chip topological insulator-based terahertz systems. However, polarization-shaped terahertz emitters based on topological insulators with an arbitrarily manipulated temporal evolution of the amplitude and the electric-field vector direction have not yet been explored. We systematically investigated the terahertz radiation from topological insulator Bi2Te3 nanofilms driven by femtosecond laser pulses and successfully realized the generation of efficient chiral terahertz waves with controllable chirality, ellipticity, and principal axis. The convenient engineering of the chiral terahertz waves was interpreted by a photogalvanic effect (PGE)-induced photocurrent, while the linearly polarized terahertz waves originated from linear PGE-induced shift currents. Our work not only provides further understanding of femtosecond coherent control of ultrafast spin currents but also describes an effective way to generate spin-polarized terahertz waves at the source.
spin-polarized terahertz manipulation topological insulator photogalvanic effect 
Advanced Photonics
2020, 2(6): 066003
Beibei Xu 1,2†Hanmeng Li 1,2Shenglun Gao 1,2Xia Hua 3[ ... ]Tao Li 1,2,*
Author Affiliations
1 Nanjing University, College of Engineering and Applied Sciences, National Laboratory of Solid State Microstructures, Key Laboratory of Intelligent Optical Sensing and Integration, Jiangsu Key Laboratory of Artificial Functional Materials, Nanjing, China
2 Collaborative Innovation Center of Advanced Microstructures, Nanjing, China
3 Nanjing University, School of Electronic Science and Engineering, Nanjing, China
Metasurfaces have demonstrated unprecedented capabilities in manipulating light with ultrathin and flat architectures. Although great progress has been made in the metasurface designs and function demonstrations, most metalenses still only work as a substitution of conventional lenses in optical settings, whose integration advantage is rarely manifested. We propose a highly integrated imaging device with silicon metalenses directly mounted on a complementary metal oxide semiconductor image sensor, whose working distance is in hundreds of micrometers. The imaging performances including resolution, signal-to-noise ratio, and field of view (FOV) are investigated. Moreover, we develop a metalens array with polarization-multiplexed dual-phase design for a wide-field microscopic imaging. This approach remarkably expands the FOV without reducing the resolution, which promises a non-limited space-bandwidth product imaging for wide-field microscopy. As a result, we demonstrate a centimeter-scale prototype for microscopic imaging, showing uniqueness of meta-design for compact integration.
metalens compact imaging device polarization multiplexing wide-field microscopy 
Advanced Photonics
2020, 2(6): 066004
Author Affiliations
University of Freiburg, Gisela and Erwin Sick Laboratory for Micro-Optics, Department of Microsystems Engineering, Freiburg, Germany
We discuss the implementation and performance of an adaptive optics (AO) system that uses two cascaded deformable phase plates (DPPs), which are transparent optofluidic phase modulators, mimicking the common woofer/tweeter-type astronomical AO systems. One of the DPPs has 25 electrodes forming a keystone pattern best suited for the correction of low-order and radially symmetric modes; the second device has 37 hexagonally packed electrodes better suited for high-order correction. We also present simulation results and experimental validation for a new open-loop control strategy enabling simultaneous control of both DPPs, which ensures optimum correction for both large-amplitude low-order, and complex combinations of low- and high-order aberrations. The resulting system can reproduce Zernike modes up to the sixth radial order with stroke and fidelity up to twice better than what is attainable with either of the DPPs individually. The performance of the new AO configuration is also verified in a custom-developed fluorescence microscope with sensorless aberration correction.
adaptive optics woofer/tweeter phase modulation optofluidics aberration correction open-loop control 
Advanced Photonics
2020, 2(6): 066005