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  • Articles  (1,724)
  • 11
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    Soliton Booting Dynamics in an Ultrafast Anomalous Dispersion Fiber Laser (2018)
    Institute of Electrical and Electronics Engineers (IEEE)
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    Publication Date: 2018-04-04
    Description: We reported on the soliton booting dynamics of an ultrafast fiber laser operating in an anomalous dispersion regime. Based on the advanced experimental methodologies of spatio-temporal reconstruction and dispersive Fourier transform (DFT), the soliton booting dynamics are analyzed in the time and spectral domains. The spectral interference pattern with strong intensity oscillation behavior was observed near the mode-locking transition. It was found that the spectral pattern distributions are induced by the transient structured soliton formation during the pulse shaping from the noise background. The experimental results were further verified by the theoretical simulations. The obtained results would provide a general guideline for understanding the soliton booting dynamics in the ultrafast fiber lasers, and will prove to be fruitful to the various communities interested in solitons and fiber lasers.
    Electronic ISSN: 1943-0655
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Published by Institute of Electrical and Electronics Engineers (IEEE)
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  • 12
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    Secure Key Distribution Strategy in OFDM-PON by Utilizing the Redundancy of Training Symbol and Digital Chaos Technique (2018)
    Institute of Electrical and Electronics Engineers (IEEE)
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    Publication Date: 2018-04-04
    Description: A secure key distribution scheme for orthogonal frequency division multiplexing (OFDM) passive optical network system is proposed and experimentally demonstrated. The training symbol (TS), which is used for time synchronization and channel estimation, is formed by adopting a noise-like chaotic sequence. The redundancy of the TS is utilized to embed secure keys. An experiment is performed, in which 7.64 Gb/s 16-quadrature-amplitude-modulation OFDM data and 28.4 Mb/s keys embedded in are successfully transmitted over 25 km standard single mode fiber. The results indicate a promising key distribution method for physical layer secure optical communication.
    Electronic ISSN: 1943-0655
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Published by Institute of Electrical and Electronics Engineers (IEEE)
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  • 13
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    Bidirectional 4-PAM to Double Per-Fiber Capacity in 2-km Intra-Datacenter Links (2018)
    Institute of Electrical and Electronics Engineers (IEEE)
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    Publication Date: 2018-04-04
    Description: This paper presents an experimental demonstration of bidirectional 4-PAM transmission for intra-datacenter links using a pair of SMF fibers. In the proposed architecture, each transceiver laser feeds both fibers, which are thus used bidirectionally to double the capacity per used fiber, wavelength, and laser. Besides the experimental demonstration, we also report a theoretical and simulative investigation on the penalty induced in this architecture by spurious connector back-reflections. We show that the resulting penalty can be kept under control for typical realistic connector reflection values, provided that each pair of lasers in both directions are separated by at least twice the system symbol rate.
    Electronic ISSN: 1943-0655
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Published by Institute of Electrical and Electronics Engineers (IEEE)
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  • 14
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    Lasing With Resonant Feedback in Weakly Modulated Parity-Time Symmetric Lattices (2018)
    Institute of Electrical and Electronics Engineers (IEEE)
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    Publication Date: 2018-04-04
    Description: We report on the lasing action in weakly modulated parity-time (PT) symmetric lattices. At the exceptional point in PT-symmetric lattices, the amplitude and phase of unidirectionally scattered waves are independently and flexibly determined by the PT modulations, thus, providing a distinctive route to construct a lasing mode in finite systems with weakly modulated structures. It is revealed that the resonant feedback mechanism plays a crucial role in building up the lasing action. Our finding would enrich the singularity dynamics in the weakly modulated PT systems.
    Electronic ISSN: 1943-0655
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Published by Institute of Electrical and Electronics Engineers (IEEE)
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  • 15
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    Microdisk Resonator With Negative Thermal Optical Coefficient Polymer for Refractive Index Sensing With Thermal Stability (2018)
    Institute of Electrical and Electronics Engineers (IEEE)
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    Publication Date: 2018-03-31
    Description: In this paper, we propose a microdisk resonator with negative thermal optical coefficient (TOC) polymer for refractive index (RI) sensing with thermal stability. The transmission characteristics and sensing performances by using quasi-TE 01 and quasi-TM 01 modes are simulated by a three-dimensional finite element method. The influences of the TOC, RI, and thickness of the polymer on the sensing performances are also investigated. The simulation results show that the RI sensitivity S n and temperature sensitivity S T with different polymers are in the ranges of 25.1–26 nm/RIU and 67.3–75.2 pm/K for the quasi-TE 01 mode, and 94.5–110.6 nm/RIU and 1.2–51.3 pm/K for the quasi-TM 01 mode, respectively. Moreover, figure-of-merit of the temperature sensing for the quasi-TM 01 mode is in the range of 2 × 10 −4 –8 × 10 –3 , which can find important application in the implementation of the adiabatic devices.
    Electronic ISSN: 1943-0655
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Published by Institute of Electrical and Electronics Engineers (IEEE)
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  • 16
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    Broadband Reflective Optical Limiter Using GST Phase Change Material (2018)
    Institute of Electrical and Electronics Engineers (IEEE)
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    Publication Date: 2018-03-31
    Description: We experimentally demonstrate a thermally induced reflective optical limiter using Ge $_2$ Sb $_2$ Te $_5$ (GST) and SiO $_2$ in a multilayer photonic bandgap edge-filter configuration. In the PASS state, greater than 80% transmission was achieved at $lambda sim 1500$  nm over a 300 nm spectral bandwidth and $pm 45^{circ }$ angles of incidence. In the BLOCK state, extinction ratios higher than 30 dB were achieved. By comparison, all previous optical limiters based on nonlinear photonic crystals have severe spectral bandwidth and/or angle of incidence limitations in either the PASS or BLOCK states. A nine-layer implementation of this device was fabricated and tested in this paper. Numerical modeling results show reasonable agreement with measured values. To the best of our knowledge, this is the first demonstration of optical limiting over a broad spectral band using phase change materials with this level of performance. However, it should be noted that although GST can be switched in both directions, the experimental results demonstrated in this paper are limited to PASS-to-BLOCK switching only.
    Electronic ISSN: 1943-0655
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Published by Institute of Electrical and Electronics Engineers (IEEE)
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  • 17
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    A Real-Time Restraint Method for Range Walk Error in 3-D Imaging Lidar Via Dual Detection (2018)
    Institute of Electrical and Electronics Engineers (IEEE)
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    Publication Date: 2018-03-31
    Description: Geiger-mode avalanche photodiode (Gm-APD) offers 3D imaging lidar much better capability in terms of detection sensitivity. However, a range walk error (RWE) exists in Gm-APDs which refers to the fluctuation of the measured distance as a function of the intensity of echo pulses. In this paper, we present a real-time restraint method for RWE implemented by unequally intensity-dividing the echo pulses into two Gm-APDs. The difference image of two depth images measured by the divided beams is a matrix of RWE distribution and the intensity image is used to censor the anomalous pixels in the matrix. Combined with the matrix of RWE distribution, an accurate depth image with low RWE can be obtained. Experimental results demonstrate that the proposed method reduces approximately 86% RWE of the conventional method in real time.
    Electronic ISSN: 1943-0655
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Published by Institute of Electrical and Electronics Engineers (IEEE)
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  • 18
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    Ultraviolet-A LED Based on Quantum-Disks-In-AlGaN-Nanowires—Optimization and Device Reliability (2018)
    Institute of Electrical and Electronics Engineers (IEEE)
    Details
    Publication Date: 2018-03-31
    Description: Group-III nitride-based ultraviolet (UV) quantum-disks (Qdisks) nanowires (NWs) light-emitting diodes grown on silicon substrates offer a scalable, environment-friendly, compact, and low-cost solution for numerous applications in solid-state lighting, spectroscopy, and biomedical. However, the internal quantum efficiency, injection efficiency, and extraction efficiency need to be further improved. The focus of this paper encompasses investigations based on structural optimization, device simulation, and device reliability. To optimize a UV-A (320–400 nm) device structure, we utilize the self-assembled Qdisks NWs with varying Qdisks thickness to study carrier separation in active-region and implement an improved p-contact-layer to increase the output power. By simulation, we found a 100× improvement in the direct recombination rate for samples with thicker Qdisks thickness of ∼5 monolayers (MLs) compared to the sample with ∼2 MLs-thick Qdisks. Moreover, the sample with graded top Mg-doped AlGaN layer in conjunction with thin Mg-doped GaN layer shows 10× improvement in the output power compared to the samples with thicker top Mg-doped GaN absorbing contact layer.  A fitting with ABC model revealed the increase in nonradiative recombination centers in the active region after a soft stress test.  This paper aims to shed light on the research efforts required for furthering the UV NWs LED research for practical applications.
    Electronic ISSN: 1943-0655
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Published by Institute of Electrical and Electronics Engineers (IEEE)
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  • 19
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    GaN Membrane With Nano-Grooves for Single-Band Coupling in the Entire Visible Wavelength Range (2018)
    Institute of Electrical and Electronics Engineers (IEEE)
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    Publication Date: 2018-03-31
    Description: Nano-groove arrays incorporated into a freestanding GaN membrane are proposed for coupling with visible light. The coupling of transverse electric mode light over the entire visible wavelength region into and out of the planar membrane is thoroughly investigated herein by performing a finite element method analysis. Coupling can be regulated by device parameters such as groove depth, membrane thickness, grating period, and duty cycle. Single-band coupling featuring tunable coupling bands can be realized, with the peak dual coupling efficiency reaching 0.55. This study paves the way for realizing planar photonics devices at specific single wavelengths. The proposed device is a suitable candidate for use in optical filters, de-multiplexers, planar photonic sensors, and other devices.
    Electronic ISSN: 1943-0655
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Published by Institute of Electrical and Electronics Engineers (IEEE)
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  • 20
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    Pixel-Reassigned Spectral-Domain Optical Coherence Tomography (2018)
    Institute of Electrical and Electronics Engineers (IEEE)
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    Publication Date: 2018-03-31
    Description: A novel method of pixel reassignment (PRA) is proposed to achieve transverse superresolution in the confocal microscopy. Inspired by it, for the first time, we report a pixel-reassigned spectral-domain optical coherence tomography (OCT) with $sim$ 1.5 times transverse resolution improvement both in numerical simulations and imaging experiments. PRA is implemented by transversely shifting the detection fiber from the on-axis position to five off-axis positions, capturing cross-sectional images at each shifting step of the detection fiber and digitally reassigning them together to give a sharper image with moderately extended depth of focus and enhanced intensity. So, we believe that the PRA technique will improve the imaging performance and be beneficial to the development of the OCT community.
    Electronic ISSN: 1943-0655
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Published by Institute of Electrical and Electronics Engineers (IEEE)
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