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Accepted papers to appear in an upcoming issue

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Effect of anti-crossings with cladding resonances on ultrafast nonlinear dynamics in gas-filled PCFs

Francesco Tani, Felix Köttig, David Novoa, Ralf Keding, and Philip Russell

Doc ID: 307635 Received 22 Sep 2017; Accepted 21 Nov 2017; Posted 21 Nov 2017  View: PDF

Abstract: Spectral anti-crossings between the fundamental guided mode and core wall resonances alter the dispersion in hollow-core anti-resonant-reflection photonic crystal fibers. Here we study the effect of this dispersion change on the nonlinear propagation and dynamics of ultrashort pulses. We find that it causes emission of narrow spectral peaks through a combination of four-wave mixing and dispersive wave emission. We further investigate the influence of the anti-crossings on nonlinear pulse propagation and show that their impact can be minimized by adjusting the core-wall thickness in such a way that the anti-crossings lie spectrally distant from the pump wavelength.

Mode selection and dispersion engineering in Bragg-like slot photonic crystal waveguides for hybrid light-matter interactions

Samuel Serna Otálvaro, Weiwei Zhang, Thi Hong Cam Hoang, Carlos Alonso Ramos, Delphine Marris-Morini, Laurent Vivien, and Eric Cassan

Doc ID: 301359 Received 04 Jul 2017; Accepted 21 Nov 2017; Posted 22 Nov 2017  View: PDF

Abstract: We introduce a family of slot photonic crystal waveguides (SPhCW) for the hybrid integration of low index active materials in silicon photonics with energy confinement factors of 30% in low index regions. The proposed approach, which is based on a periodic indentation of the etched slot in the middle of the SPhCW, makes it possible to reconcile a simultaneously narrow and wide slot for exploiting the two modes of even symmetry of SPhCW. The resulting mode selection mechanism allows a flexible choice of the modes to be used. Furthermore, the proposed structure offers tremendous flexibility for adjusting the dispersive properties of the slot-confined modes, in particular of their slow light effects. Flat band slow light in a bandwidth of about 60 nm with a group velocity dispersion factor |β₂| below 1 ps²/mm is numerically demonstrated by this approach, corresponding to a normalized delay bandwidth product (NDBP) of around 0.4. These results, obtained from hollow core periodic waveguides that are directly designed in view of hybrid integration of active materials in mechanically robust structures (not based on free standing membranes), could pave the way for the realization of on chip slow light bio-sensing, active hybrid-silicon optoelectronic devices or all optical hybrid-silicon nonlinear functionalities.

All-fiber-photonics-based ultralow-noise agile frequency synthesizer for X-band radars

Juan Wei, Dohyeon Kwon, Shuangyou Zhang, Shilong Pan, and Jungwon Kim

Doc ID: 307777 Received 02 Oct 2017; Accepted 16 Nov 2017; Posted 16 Nov 2017  View: PDF

Abstract: We propose and demonstrate an agile X-band signal synthesizer with ultralow phase noise based on all-fiber photonic techniques for radar applications. It shows phase noise of -145 dBc/Hz (-152 dBc/Hz) at 10-kHz (100-kHz) offset frequency for 10-GHz carrier frequency with integrated rms timing jitter between 7.6 fs and 9.1 fs [integration bandwidth: 10 Hz – 10 MHz] for frequencies from 9 to 11 GHz. Its frequency switching time is evaluated to be 135 ns with 135 pHz frequency tuning resolution. In addition, the X-band linear-frequency-modulated signal generated by the proposed synthesizer shows a good pulse compression ratio approximating the theoretical value. In addition to the ultra-stable X-band signals, the proposed synthesizer can also provide 0-1 GHz ultralow-jitter clocks for ADC and DAC in radar systems and ultralow-jitter optical pulse trains for photonic ADC in photonic radar systems. The proposed X-band synthesizer shows great performance in phase stability, switching speed and modulation capability with robustness and potential low-cost, which is enabled by all-fiber-photonics platform, and can be a compelling technology suitable for future X-band radars.

Ultra-deep-subwavelength Light Transmission in Hybrid Nanowire-loaded Silicon Nano-rib Waveguides

Yusheng Bian, Qiang Ren, Lei Kang, Taiwei Yue, Pingjuan Werner, and Douglas Werner

Doc ID: 305768 Received 31 Aug 2017; Accepted 14 Nov 2017; Posted 15 Nov 2017  View: PDF

Abstract: Hybrid plasmonic waveguides leveraging the coupling between dielectric modes and plasmon polaritons have emerged as a major focus of research attention during the past decade. A feasible way for constructing practical hybrid plasmonic structures is to integrate metallic configurations with silicon-on-insulator waveguiding platforms. Here we report a transformative high-performance silicon-based hybrid plasmonic waveguide that consists of a silicon nano-rib loaded with a metallic nanowire. An ultra-deep-subwavelength mode area (lambda^2/4.5×10^5 ~lambda^2/7×10^3), in conjunction with a reasonable propagation distance (2.2 ~ 60.2 um), is achievable at a telecommunication wavelength of 1.55 um. Such a nano-rib-based waveguide outperforms its conventional hybrid and plasmonic waveguiding counterparts, demonstrating tighter optical confinement for similar propagation distances, and a significantly enhanced figure of merit. The guiding properties of the fundamental mode are also quite robust against possible fabrication imperfections. Due to the strong confinement capability, our proposed hybrid configuration features ultra-low waveguide crosstalk, and enables sub-micron bends with moderate attenuations as well. The outstanding optical performance renders such waveguides as promising building blocks for ultra-compact passive and active silicon-based integrated photonic components.

Polarization-independent all-silicon dielectric metasurfaces in the terahertz regime

Huifang Zhang, Xueqian Zhang, Quan Xu, Qiu Wang, Yue Hong Xu, Minggui Wei, Yanfeng Li, Jianqiang Gu, Tian Zhen, Chunmei Ouyang, Xixiang Zhang, Cong Hu, Jiaguang Han, and Weili Zhang

Doc ID: 303917 Received 03 Aug 2017; Accepted 13 Nov 2017; Posted 15 Nov 2017  View: PDF

Abstract: Dielectric metasurfaces have achieved great success in realizing high-efficiency wavefront control in the optical and infrared ranges. Here, we experimentally demonstrate several efficient, polarization-independent, all-silicon dielectric metasurfaces in the terahertz regime. The metasurfaces are composed of cylindrical silicon pillars on a silicon substrate, which can be easily fabricated using etching technology for semiconductors. By locally tailoring the diameter of the pillars, full control over abrupt phase changes can be achieved. To show the controlling ability of the metasurfaces, an anomalous deflector, two Bessel beam generators, and three vortex beam generators are fabricated and characterized. We also show that the proposed metasurfaces can be easily combined to form composite devices with extended functionalities. The proposed controlling method has promising applications in developing low-loss, ultra-compact spatial terahertz modulation devices.

Enhanced light emission from AlGaN/GaN multiple quantum wells using localized surface plasmon by aluminum nanoring patterns

Kyungrock son, Byeongryong Lee, Min-ho Jang, Hyun-chul park, Yong-Hoon Cho, and Tae-Geun Kim

Doc ID: 305263 Received 12 Sep 2017; Accepted 11 Nov 2017; Posted 15 Nov 2017  View: PDF

Abstract: We investigate the localized surface plasmon (LSP) effect by Al nanorings on the AlGaN/GaN multiple quantum well (MQW) structure emitting at 365 nm. For this experiment, first, the size of Al nanorings is optimized to maximize the energy transfer (or coupling) between the LSP and MQW using the silica nanospheres. Then, the Al nanorings with an outer diameter of 385 nm, which exhibit a strong absorption peak in the near-UV region, is applied to the top surface of the AlGaN/GaN MQW. The photoluminescence (PL) intensity of the MQW structure with Al nanorings increased by 227% at 365 nm compared to that without Al nanorings. This improvement is mainly attributed to an enhanced radiative recombination rate in the MQWs through the energy-matched LSPs by the temperature-dependent PL and time-resolved PL analyses. The radiative lifetime was about two-times shorter than that of the structure without Al nanorings at room temperature. In addition, the measured PL efficiency at room temperature of the structure with Al nanorings was 33%, while that of the structure without Al nanorings was 19%, implying that LSP-QW coupling together with the nanoring array pattern itself played important roles in the enhancement.

Terahertz spoof surface-plasmon-polariton subwavelength waveguide

Ying Zhang, Yue Hong Xu, Chunxiu Tian, Quan Xu, Xueqian Zhang, Yanfeng Li, Xixiang Zhang, Jiaguang Han, and Weili Zhang

Doc ID: 308112 Received 27 Sep 2017; Accepted 08 Nov 2017; Posted 10 Nov 2017  View: PDF

Abstract: Surface plasmon polaritons (SPPs) with the features of subwavelength confinements and strong enhancements have sparked enormous interest. However, in the terahertz regime, due to perfect conductivity of most metals, it is hard to realize a strong confinement of SPPs although a propagation loss could be sufficiently low. One main approach to circumvent this problem is to exploit the named spoof SPPs, which are expected to exhibit useful subwavelength confinement and relative low propagation loss at terahertz frequencies. Here we report the design, fabrication and characterization of terahertz spoof SPPs waveguide based on the corrugated metal surface. The various waveguide components including: straight waveguide, S-bend waveguide, Y-splitter and directional coupler were experimentally demonstrated using scanning near-field terahertz microscopy. The proposed waveguide indeed enables propagating, bending, splitting and coupling of terahertz SPPs and it thus would pave a new way for the development of flexible and compact plasmonic circuits operating at terahertz frequencies

A Single-Chip Si Optical Single-Sideband Modulator

Byung-Min Yu, Jeong-Min Lee, Christian Mai, Stefan Lischke, Lars Zimmermann, and Woo-Young Choi

Doc ID: 306504 Received 08 Sep 2017; Accepted 01 Nov 2017; Posted 03 Nov 2017  View: PDF

Abstract: We demonstrate an integrated Si optical single-sideband (OSSB) modulator composed of a ring-assisted mach-zehnder modulator (RA-MZM) and a quadrature hybrid coupler (QHC). Both RA-MZM and QHC are carefully designed for 30-GHz opearation and their operations are verified by measurement. The Si OSSB modulator successfully generates a single sideband with larger than 15 dB suppression of the undesired sideband.

Generation of high-energy narrowband 2.05 µm pulses for seeding a Ho:YLF laser

Yanchun Yin, Xiaoming Ren, YANG WANG, Fengjiang Zhuang, Jie Li, and Zenghu Chang

Doc ID: 307697 Received 22 Sep 2017; Accepted 31 Oct 2017; Posted 03 Nov 2017  View: PDF

Abstract: We experimentally demonstrated efficient generation of high-energy (82 μJ) narrowband 2.05 μm pulses pumped with 1 mJ broadband Ti:Sapphire laser pulses, utilizing dual-chirped optical parametric amplification (DC-OPA) in a BBO crystal. The narrowband 2.05 μm pulses will be primarily used for seeding a Ho:YLF laser, which solves the synchronization issue when both the Ti:Sapphire laser and the Ho:YLF laser are needed for developing mid-infrared lasers. The narrowband 2.05 μm pulse from the unique DC-OPA design can seed the Ho:YLF laser much more efficiently than the broadband 2.05 μm pulse from the traditional OPA technology.

Nonlinearity-tailored fiber laser technology for low-noise, ultra-wide-band tunable femtosecond light generation

Xiaomin Liu, Jesper Laegsgaard, Roman Iegorov, Ask Svane, F Omer Ilday, Haohua Tu, Stephen Boppart, and Dmitry Turchinovich

Doc ID: 303292 Received 31 Jul 2017; Accepted 26 Oct 2017; Posted 31 Oct 2017  View: PDF

Abstract: The emission wavelength of a laser is physically pre-determined by the gain medium used. Consequently, arbitrary wavelength generation is a fundamental challenge in the science of light. Present solutions include optical parametric generation, requiring complex optical setups; and spectrally-sliced supercontinuum, taking advantage of simpler fiber technology: a fixed-wavelength pump laser pulse is converted into a spectrally very broadband output, from which the required resulting wavelength is then optically filtered. Unfortunately, this process is associated with inherently poor noise figure, which often precludes many realistic applications of such supercontinuum sources. Here, we show that by adding only one passive optical element - a tapered photonic crystal fiber - to a fixed-wavelength femtosecond laser, one can in a very simple manner resonantly convert the laser emission wavelength into an ultra-wide and continuous range of desired wavelengths, with very low inherent noise, and without mechanical realignment of the laser. This is achieved by exploiting the double interplay of nonlinearity and chirp in the laser source and chirp and phase-matching in the tapered fiber. As a first demonstration of this simple and inexpensive technology, we present a femtosecond fiber laser continuously tunable across the entire red-green-blue spectral range.

Capacitive actuation and switching of Add-Drop graphene-silicon micro-ring filters

Tommaso Cassese, Marco Giambra, Vito Sorianello, Gabriele De Angelis, Michele Midrio, Marianna Pantouvaki, Joris Van Campenhout, Inge Asselberghs, Cedric Huyghebaert, Antonio D'Errico, and Marco Romagnoli

Doc ID: 303062 Received 25 Jul 2017; Accepted 27 Sep 2017; Posted 28 Sep 2017  View: PDF

Abstract: We propose and experimentally demonstrate capacitive actuation of a graphene-silicon micro-ring add/drop filter. The mechanism is based on a silicon-SiO2-graphene capacitor on top of the ring waveguide. We show the capacitive actuation of the add/drop functionality by a voltage driven change of the graphene optical absorption. The proposed capacitive solution overcomes the need of continuous heating to keep tuned the filter in/out resonance and therefore eliminates ‘in operation’ energy consumption.

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