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Accepted papers to appear in an upcoming issue

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All-in-fiber amplification and compression of frequency-shifted solitons tunable in the 1800-2000 nm range

Grzegorz Sobon, Tadeusz Martynkien, Karol Tarnowski, Pawel Mergo, and Jaroslaw Sotor

Doc ID: 320061 Received 17 Jan 2018; Accepted 19 Feb 2018; Posted 21 Feb 2018  View: PDF

Abstract: We report an all-fiber, all-polarization maintaining (PM) source of widely tunable (1800 – 2000 nm) ultrashort pulses based on amplification of self-frequency-shifted solitons generated in a highly nonlinear fiber pumped with an Er-doped fiber laser. The system delivers sub-100 fs pulses with energies up to 8.6 nJ and is built entirely from polarization maintaining optical fibers, without any free-space optics. The all-fiber, all-PM, alignment-free design significantly increases the suitability of such source for field deployments.

On-chip cyclic-AWG-based 12 × 12 silicon wavelength routing switches with minimized port-to-port insertion loss fluctuation

Zepeng Pan, Songnian Fu, Luluzi Lu, Dongyu Li, Weijie Chang, Deming Liu, and Minming Zhang

Doc ID: 315662 Received 13 Dec 2017; Accepted 18 Feb 2018; Posted 20 Feb 2018  View: PDF

Abstract: With rapidly increasing bandwidth requirement of optical communication networks, compact and low-cost large scale optical switches become necessary. Silicon photonics is a promising technology due to its small footprint, cost competitiveness and high bandwidth density. In this paper, we demonstrate a 12 × 12 silicon wavelength routing switches employing cascaded AWGs connected by silicon waveguide interconnection network on a single chip. We optimize the connecting strategy of the crossing structure to reduce its footprint. And we develop an algorithm based on minimum standard derivation to minimize the port-to-port IL fluctuation of the switch globally. The simulated port-to-port IL fluctuation decreases by about 3 dB compared with the conventional one. The fluctuation of the measured port-to-port IL is only 1.68 dB with a standard deviation of 0.51 dB. The device can be used for wide applications in core networks and data centers.

Chimera States in Plasmonic Nanoresonators

Eesa Rahimi and Ibrahim Sendur

Doc ID: 312721 Received 03 Nov 2017; Accepted 15 Feb 2018; Posted 16 Feb 2018  View: PDF

Abstract: The chimera state is the concurrent combination of synchronous and incoherent oscillations in a set of identical oscillators. In this study, we demonstrate the states for optical nanoresonators where the oscillators are designed based on a plasmonic dimer cavity. This resonator interchanges radiative energy with an active medium located at its hot-spot, and therefore, forms an amplitude mediated oscillating system. Finite-difference time-domain (FDTD) based numerical analysis of a circular array of the coupled oscillators reveals that regardless of identical nature, oscillator phase is not concordant over time for all members. The effect of coupling strength on the phase escape/synchronization of the oscillators is investigated for the plasmonic nanoresonator system. It is shown that for identical oscillators, which are placed symmetrically over the perimeter of a disc, the array can be divided to several subgroups of concurrent coherent and incoherent members. While the oscillator of each subgroup seems to be locked together, one member can escape from synchronization for a while and return to coherency or it can sync with the other groups. The effect of coupling strength and number of oscillators on the phase escape pace is studied for this system and strong coupling is shown to force the array members to fully synchronize while weaker coupling causes chimera states in the array.

Integrated Heterogeneous Silicon/III-V Mode-Locked Lasers

Michael Davenport, John Bowers, and Songtao Liu

Doc ID: 318990 Received 12 Jan 2018; Accepted 15 Feb 2018; Posted 16 Feb 2018  View: PDF

Abstract: The mode-locked laser diode has emerged as a promising candidate as a signal source for photonic radar systems, wireless data transmission, and frequency comb spectroscopy. They have the advantage of small size, low cost, high reliability, and low power consumption, thanks to semiconductor technology. Mode-locked lasers based on silicon photonics advance these qualities by the use of highly advanced silicon manufacturing technology. This paper will begin by giving an overview of mode-locked laser diode literature, and then focus on mode-locked lasers on silicon. The dependence of mode locked laser performance on design details is presented.

Band gap tailored random laser

hongbo lu, jian xing, Cheng Wei, Jiangying Xia, Junqing Sha, Yunsheng Ding, Guobing Zhang, Longzhen Qiu, Kang Xie, and Hu Zhijia

Doc ID: 318385 Received 28 Dec 2017; Accepted 12 Feb 2018; Posted 13 Feb 2018  View: PDF

Abstract: A random laser based band gap tailored with a wide tunable range and low threshold through infrared radiation is demonstrated. When dope fluorescent dyes into the liquid crystal and heavily doped chiral agent system, we demonstrate the wavelength tuning random laser that instead of the side-band laser, which is caused by the combined effect of multi-scattering of LC and band gap control. Through rotating the infrared absorbing material on the side of the liquid crystal cell, the adjustable range for random lasing of 80 nm by infrared light irradiation was observed.

Experimental realization to sort efficiently vector beams by polarization topological charge via Pancharatnam-Berry phase modulation

Shuiqin Zheng, Ying Li, QINGGANG LIN, Xuanke Zeng, Guoliang Zheng, Yi Cai, Zhenkuan Chen, Shixiang Xu, and Dianyuan Fan

Doc ID: 312504 Received 17 Nov 2017; Accepted 11 Feb 2018; Posted 13 Feb 2018  View: PDF

Abstract: This paper reports the experimental realization of sorting efficiently vector beams by polarization topological charge (PTC). PTC of a vector beam can be defined as the repetition number of polarization state change along the azimuthal axis, with its sign standing for the rotating direction of the polarization. Here, a couple of liquid crystal Pancharatnam-Berry optical elements (PBOEs) have been used to introduce conjugated spatial phase modulations for two orthogonal circular polarization states. Applying these PBOEs in a 4-f optical system, our experiments show the setup can work for PTC sorting with its separation efficiency more than 58%. This work provides with an effective way to decode information from different PTCs, which may be interesting in many fields, especially in optical communication.

All-silicon carrier accumulation modulator based on a lateral MOS-capacitor

Kapil Debnath, David Thomson, Weiwei Zhang, Ali Khokhar, Callum Littlejohns, James Byers, Lorenzo Mastronardi, Muhammad Husain, Kouta Ibukuro, Frederic Gardes, Graham Reed, and Shin-ichi Saito

Doc ID: 318121 Received 20 Dec 2017; Accepted 10 Feb 2018; Posted 13 Feb 2018  View: PDF

Abstract: In silicon photonics, the carrier depletion scheme has been the most commonly used mechanism for demonstrating high speed electro-optic modulation. However, in terms of phase modulation efficiency, carrier accumulation based devices potentially offer almost an order of magnitude improvement over those based on carrier depletion. Previously reported accumulation modulator designs only considered vertical metal-oxide-semiconductor (MOS)-capacitors, which imposes serious restrictions on the design flexibility and integratability with other photonic components. In this work, for the first time we design and experimentally demonstrate an all-silicon accumulation phase modulator based on a lateral MOS-capacitor. Using a Mach-Zehnder interferometer (MZI) modulator with a 500-µm-long phase-shifter, we demonstrate high speed modulation up to 25 Gbit/s with a modulation efficiency (VπLπ) of 1.53 V-cm.

Active Macroscale Visible Plasmonic Arrays

Yue Li, Jian Li, Taixing Huang, Fei Huang, Jun Qin, Lei Bi, Jianliang Xie, Longjiang Deng, and Bo Peng

Doc ID: 309545 Received 25 Oct 2017; Accepted 10 Feb 2018; Posted 13 Feb 2018  View: PDF

Abstract: Although plasmonic nanostructure has attracted widespread research interest in recent years, it is still a major challenge to realize large-scale active plasmonic nanostructures operation in the visible optical frequency. Herein, we demonstrate a heterostructure geometry comprising a centimeter-scale Au nanoparticle monolayer and VO2 films, in which the plasmonic peak is inversely tuned between 685 nm and 618 nm by heating process since the refractive index will change when VO2 films undergo the transition between the insulating phase and the metallic phase. Simultaneously, the phase transition of VO2 films can be improved by plasmonic arrays due to plasmonic enhanced light absorption and photothermal effect. The phase transition temperature for Au/VO2 films is lower than bare VO2 films and can decrease to room temperature (RT) under the laser irradiation. For light-induced phase transition of VO2 films, the laser power of Au/VO2 films phase transition is ~28.6% lower than bare VO2 films. Our works raise the feasibility to use active plasmonic arrays in the visible region.

Self-Locked Orthogonal Polarized Dual-Comb in a Microresonator

Weiqiang Wang, Wenfu Zhang, zhizhou lu, Sai Tak Chu, Brent Little, Qinghua Yang, Lei wang, and Wei Zhao

Doc ID: 317884 Received 26 Dec 2017; Accepted 09 Feb 2018; Posted 09 Feb 2018  View: PDF

Abstract: Dual-comb is an emerging tool to obtain unprecedented test range as well as ultrahigh sensitivity, resolution, accuracy and updating rate in molecular spectroscopy, optical metrology and optical frequency synthesis. The recent progress in chip-based microcombs has promoted the on-chip dual-comb measuring systems to a new phase attributed to the large frequency spacing and broad optical frequency range. In this paper, we proof-of-concept demonstrate dual-comb generation with orthogonal polarization states in a single microresonator through pumping both of the TE and TM modes simultaneously. The generated dual-comb exhibits excellent stability due to the intrinsic feedback mechanism of the self-locked scheme which are used to generate the two vertical pumps in our experiments. The frequency spacing of the two orthogonal combs is slightly different because of the different properties of the mode family. Such orthogonal polarized dual-comb in a microresonator could be a new comb source for out-of-lab applications in the fields of integrated spectroscopy, ranging measurement, optical frequency synthesis, as well as microwave comb generation.

Necklaces of PT-symmetric dimers

Diana Nodal Stevens, Benjamin Jaramillo Ávila, and Blas Rodriguez-Lara

Doc ID: 306303 Received 05 Sep 2017; Accepted 09 Feb 2018; Posted 09 Feb 2018  View: PDF

Abstract: We study light propagation through cyclic arrays, composed by copies of a given PT-symmetric dimer, using a group theoretical approach and finite element modeling. The theoretical mode-coupling analysis suggest the use of these devices as output port replicators where the dynamics are controlled by the impinging light field. This is confirmed to good agreement with finite element propagation in an experimentally feasible necklace of passive PT-symmetric dimers constructed from lossy and lossless waveguides.

Switchable wavelength vortex beams based on polarization-dependent micro-knot resonator

jinqiu zheng, Ao Yang, Teng Wang, Xianglong Zeng, Ning Cao, Mei Liu, Fufei Pang, and Tingyun Wang

Doc ID: 314915 Received 06 Dec 2017; Accepted 08 Feb 2018; Posted 09 Feb 2018  View: PDF

Abstract: We experimentally demonstrated a method of generating continuously switchable wavelength optical vortex beams in an all-fiber laser. A polarization-dependent micro-knot resonator (MKR) functions as comb filter and accounts for the narrow linewidth (0.16 nm) of multi-wavelength channels. The wavelength interval corresponds to the free spectral range of the MKR. We exploit a fused SMF-FMF mode coupler to obtain broadband mode conversion and achieve switchable multi-wavelength OVBs successfully. As far as we know, this is the first report about identical multi-wavelength vortex beams with topological charges of ±1. It has been verified that each channels of vortex beam preserve same OAM properties through their clear spiral interferograms. Multi-wavelength vortex beams with identical OAM are desirable for multiplexing, exchanging and routing to further improve the capacity of the optical fiber transmission.

High performance AlGaInP light-emitting diodes integrated on Silicon through superior quality germanium-on-insulator (GOI)

Yue Wang, Bing Wang, Wardhana Aji Sasangka, shuyu bao, Yiping Zhang, Hilmi Demir, Jurgen Michel, Kenneth Lee, Soon Fatt Yoon, Eugene Fitzgerald, Chuan Seng Tan, and Kwang Hong Lee

Doc ID: 318578 Received 28 Dec 2017; Accepted 06 Feb 2018; Posted 06 Feb 2018  View: PDF

Abstract: High performance GaInP/AlGaInP multi-quantum wells (MQWs) light-emitting diodes (LEDs) grown on a low-dislocation density (TDD) germanium-on-insulator (GOI) substrate has been demonstrated. The low TDD of the GOI substrate is realized through Ge epitaxial growth, wafer bonding, and layer transfer processes on 200 mm wafers. With O₂ annealing, the TDD of the GOI substrate can be reduced to ~1.2 × 10⁶ /cm². LEDs fabricated on this GOI substrate exhibit record high optical output power of 1.3 mW at a 670 nm peak wavelength under 280 mA current injection. This output power level is at least 2× higher compared to other reports of similar devices on silicon (Si) substrate without degrading the electrical performance. These results demonstrate great promise for the monolithic integration of visible band optical sources with Si-based electronic circuitry and realization of high density RGB (red, green, and blue) micro-LED arrays with control circuitry.

Broadening and enhancing of 2.7 μm emission spectra in Er/Ho co-doped oxyfluoride germanosilicate glass ceramics by imparting multiple local structures to rare earth ions

Qunhuo Liu, Ying Tian, Wenhua Tang, Feifei Huang, Xufeng Jing, Junjie Zhang, and Shiqing Xu

Doc ID: 314959 Received 08 Dec 2017; Accepted 06 Feb 2018; Posted 06 Feb 2018  View: PDF

Abstract: Er/Ho codoped oxyfluoride germanosilicate glass and glass ceramics were prepared and compared. The results indicate that the glass consists of SiO4 and GeO4 structural units while the network of the glass ceramics consists of SiO4, GeO4 and GeO6 units together with NaYF4 nanocrystals. The presence of multiple local structures in glass ceramics creates a range of dipole environments which is beneficial to the broadening of 2.7 μm emission. Two other reasons are attributed to the broadening of 2.7 μm emission in glass ceramics: the energy level splitting of Er3+ and the enhancement of Ho3+: 5I6→5I7 transition in NaYF4 nanocrystals.

Noise-sidebands-free and ultra-low-RIN 1.5 μm single-frequency fiber laser towards coherent optical detection

Qilai Zhao, Zhitao Zhang, Bo Wu, Tianyi Tan, Changsheng Yang, Jiulin Gan, Huihui Cheng, Zhouming Feng, Mingying Peng, Zhongmin Yang, and Shanhui Xu

Doc ID: 317939 Received 18 Dec 2017; Accepted 06 Feb 2018; Posted 06 Feb 2018  View: PDF

Abstract: A noise-sidebands-free and ultra-low relative intensity noise (RIN) 1.5 μm single-frequency fiber laser (SFFL) is demonstrated for the first time to our best knowledge. Utilizing a self-injection locking framework and a booster optical amplifier, the noise sidebands with a relative amplitudes as high as 20 dB are completely suppressed. The RIN is remarkably reduced over 64 dB at the relaxation oscillation peak to retain below -150 dB/Hz in the frequency range from 75 kHz to 50 MHz, while the quantum noise limit is -152.9 dB/Hz. Furthermore, the laser linewidth of narrow than 600 Hz, the polarization-extinction ratio of over dB, the optical signal-to-noise ratio of more than 73 dB are acquired simultaneously. This noise-sidebands-free and ultra-low-RIN SFFL is highly competitive in the advanced coherent light detection fields including coherent Doppler wind Lidar, high-speed coherent optical communication, and precise absolute distance coherent measurement.

1.3 μm InAs/GaAs quantum dot lasers on silicon with GaInP upper cladding layers

Jun Wang, Haiyang Hu, Haiying Yin, Yiming Bai, Jian Li, xin Wei, Yuanyuan Liu, Yongqing Huang, Xiaomin Ren, and Huiyun Liu

Doc ID: 315568 Received 12 Dec 2017; Accepted 04 Feb 2018; Posted 06 Feb 2018  View: PDF

Abstract: We report on the first electrically pumped continuous-wave (CW) InAs/GaAs quantum dot (QD) laser grown on Si with a GaInP upper cladding layer. A QD laser structure with a Ga0.51In0.49P upper cladding layer and an Al0.53Ga0.47As lower cladding layer was directly grown on Si by metal-organic chemical vapor deposition. It demonstrates the post-growth annealing effect on the QDs was relieved enough with the GaInP upper cladding layer grown at a low temperature of 550 ℃. The broad-stripe edge-emitting lasers with 2-mm cavity length and 15-μm stripe width were fabricated and characterized. Under CW operation, room-temperature lasing at ~1.3 μm has been achieved with a threshold density of 737 A/cm2 and a single-facet output power of 21.8 mW.

Ultra-compact and broad-band electro-absorption modulator using epsilon-near-zero conductive oxide

Qian Gao, Erwen Li, and Alan Wang

Doc ID: 318575 Received 03 Jan 2018; Accepted 03 Feb 2018; Posted 06 Feb 2018  View: PDF

Abstract: Transparent conductive oxides (TCOs) have emerged as a new type of plasmonic materials and demonstrated unique electro-optic (E-O) modulation capabilities for next generation photonic devices. In this paper, we report an ultra-compact, broadband electro-absorption (EA) modulator using epsilon-near-zero (ENZ) indium-tin-oxide (ITO). The device is fabricated on standard silicon-on-insulator (SOI) platform through the integration with a 3μm long, 300nm wide gold plasmonic slot waveguide. The active E-O modulation region consists of a metal-HfO2-ITO capacitor that can electrically switch the ITO into ENZ with ultra-high modulation strength of 2.62dB/μm and 1.5dB/μm in simulation and experiment, respectively. The EA modulator also demonstrated a uniform E-O modulation with 70nm optical bandwidth from 1530~1600nm wavelength.

High quality 2-μm Q-switched pulsed solid state lasers using spin coating-coreduction approach Bi2Te3 topological insulators

junpeng qiao, Shengzhi Zhao, Kejian Yang, Wei-heng Sung, Wenchao Qiao, Chung-Lun Wu, Jia Zhao, Guiqiu Li, Dechun Li, Tao Li, Hong Liu, and Chao-Kuei Lee

Doc ID: 315809 Received 15 Dec 2017; Accepted 02 Feb 2018; Posted 02 Feb 2018  View: PDF

Abstract: In this paper, the fabrication process and characterization of Bi2Te3 topological insulators (TIs) synthesized by the spin coating-coreduction approach (SCCA) are reported. With this approach, high uniformity nano-crystalline TI saturable absorbers (TISAs) with large area uniform and controllable thickness are prepared. By employing these prepared TIs with different thickness as SAs in 2 μm solid-state Q-switched lasers, thickness-dependent output powers and pulse durations of the laser pulses are obtained and the result also exhibits the stability and reliability. The shortest pulse duration is as short as 3 ns and the corresponding clock amplitude jitter(CAJ) is around 2.1%, which is the shortest pulse duration in the TlSA based Q-switched 2 μm lasers to the best of our knowledge. Moreover, in comparison with the TISA synthesized by the ultrasound-assisted liquid phase exfoliation (UALPE) method, the experimental results show that lasers with SCCA synthesized TISAs have higher output powers, shorter pulse durations and higher pulse peak powers. Our work suggests that the SCCA synthesized TISAs could be used as potential SAs in pulsed lasers.

Surface enhanced Raman scattering of gold nanoparticles aggregated by gold-nanofilm-coated nanofiber

Chang Cheng, Juan Li, Hong Lei, and Baojun Li

Doc ID: 313499 Received 22 Nov 2017; Accepted 02 Feb 2018; Posted 06 Feb 2018  View: PDF

Abstract: Aggregation of metal nanoparticles plays an important role in surface enhanced Raman scattering (SERS). Here, a strategy of dynamically aggregating/releasing gold nanoparticles is demonstrated using a gold-nanofilm coated nanofiber, with the assistance of enhanced optical force and plasmonic photothermal effect. Strong SERS signals of rhodamine 6G (R6G) are achieved at the hotspots formed in the inter-particle and film-particle nanogaps. The proposed SERS substrate was demonstrated to have a sensitivity of 10¯¹² M, reliable reproducibility and good stability.

Type-II Micro-Comb Generation in a Filter-Driven Four Wave Mixing Laser

Hualong Bao, Andrew Cooper, Sai Tak Chu, David Moss, Roberto Morandotti, Brent Little, Marco Peccianti, and Alessia Pasquazi

Doc ID: 312596 Received 03 Nov 2017; Accepted 30 Jan 2018; Posted 01 Feb 2018  View: PDF

Abstract: We experimentally demonstrate the generation of highly coherent type-II micro-combs based on a micro-resonator nested in a fibre cavity loop, known as the Filter-Driven Four Wave Mixing Laser (FD-FWM) scheme. In this system, the frequency spacing of the comb can be adjusted to integer multiples of the free-spectral range (FSR) of the nested micro-resonator by properly tuning the fibre cavity length. Sub-comb lines with single FSR spacing around the primary comb lines can be generated. Such a spectral emission is known as a ‘type-II comb’. Our system achieves a fully coherent output. This behaviour is verified by numerical simulations. This study represents an important step forward in controlling and manipulating the dynamics of a FD-FWM laser

Graphitic carbon nitride, a saturable absorber material for visible waveband

Mengxia Wang, Fukun Ma, zhengping wang, Hu Dawei, Xin-guang Xu, and Xiaopeng Hao

Doc ID: 313152 Received 09 Nov 2017; Accepted 30 Jan 2018; Posted 01 Feb 2018  View: PDF

Abstract: For the first time, nonlinear saturable absorption of graphitic carbon nitride (g-C₃N₄) nanosheets is observed in the visible waveband. g-C₃N₄ exhibits much stronger saturable absorption in this region than in the near-infrared region, unlike other two-dimensional materials such as graphene and black phosphorus. In Z-scan experiments with picosecond laser pulses as the excitation source, the nonlinear absorption coefficient β was measured to be -2.05, -0.34, and -0.11 cm·GW-1 at 355, 532, and 650 nm, respectively. These are much larger than -0.06 cm·GW-1 at 1064 nm. This research shows that g-C₃N₄ is a powerful saturable absorber material in the visible waveband.

Evanescent-wave pumped single-mode microcavity laser from fiber of 125 μm diameter

Yuchen Wang, Shu Hu, Xiao Yang, Ruizhi Wang, Heng Li, and ChuanXiang Sheng

Doc ID: 318398 Received 26 Dec 2017; Accepted 30 Jan 2018; Posted 01 Feb 2018  View: PDF

Abstract: A microcavity laser based on evanescent-wave-coupled gain is formed using a silica fiber with diameter of 125 μm in rhodamine 6G ethanol solution. When the fiber is sticking to the cuvette wall by capillary force, using excitation of a 532 nm nanosecond pulsed laser, single mode laser emission is observed. While increasing the distance between the fiber and the cuvette wall, the typical multi-peak whispering-gallery-modes (WGM) laser emission can also be demonstrated. On the other hand, while increasing refractive index of the solution by mixing ethanol and ethylene glycol with different ratio as solvent, the single mode emission would evolve to multi-peak WGM laser emission controllably.

New clue to thorough understanding terahertz pulse generation by femtosecond laser filamentation

Jiayu Zhao, Weiwei Liu, Shichang Li, Dan Lu, Yizhu Zhang, Yan Peng, Yiming Zhu, and Songlin Zhuang

Doc ID: 307329 Received 25 Sep 2017; Accepted 29 Jan 2018; Posted 30 Jan 2018  View: PDF

Abstract: In this work, it has been demonstrated that in order to fully understand the terahertz (THz) pulse generation process during femtosecond laser filamentation, the interaction between THz wave and air plasma has to be taken into account. This interaction is mainly associated with the spatial confinement of the THz pulse by the plasma column, which could be described by the one-dimensional negative dielectric (1DND) waveguide model. Thus, only by combining the conventional four-wave mixing (4WM) and photocurrent (PC) models with 1DND, the variation of THz spectral amplitude and width obtained in experiments could be better understood. Finally, a three-step procedure, with 1DND bridging 4WM and PC models, has been established for the first time to describe the underlying mechanism of THz radiation from plasma sources.

Photonic microwave true time delays for phased array antennas using a 49GHz FSR integrated optical micro-comb source

Xingyuan Xu, Jiayang Wu, thach ngyuen, tania moein, Sai Tak Chu, Brent Little, Roberto Morandotti, Arnan Mitchell, and David Moss

Doc ID: 313144 Received 13 Nov 2017; Accepted 29 Jan 2018; Posted 30 Jan 2018  View: PDF

Abstract: We demonstrate significantly improved performance of a microwave true time delay line (TTDL) based on an integrated micro-ring resonator (MRR) Kerr optical comb source with a channel spacing of 49GHz, corresponding to 81 channels over the C-band. The broadband microcomb, with a record low free spectral range of 49GHz, results in a large number of comb lines for the TTDL, greatly reducing the size, cost, and complexity of the system. The large channel count results in a high angular resolution and wide beam steering tunable range of the phased array antenna (PAA). The enhancement of PAA’s performance matches well with theory, corroborating the feasibility of our approach as a competitive solution towards implementing compact low-cost TTDL in radar and communications systems.

Enhanced complete photonic band gap in moderate refractive index contrast chalcogenide-air system with connected-annular-rods photonic crystals

Jin Hou, Chunyong Yang, Xiaohang Li, Zhen Cao, and Shaoping Chen

Doc ID: 314396 Received 08 Dec 2017; Accepted 29 Jan 2018; Posted 30 Jan 2018  View: PDF

Abstract: Connected-annular-rods photonic crystals (CARPC) in both triangular and square lattices are proposed to enhance the two-dimensional complete photonic bandgap (CPBG) for chalcogenide material systems with moderate refractive index contrast. For the typical chalcogenide-glass—air system with index contrast of 2.8:1, the optimized square lattice CARPC exhibits a significantly larger normalized CPBG of about 13.50 %, though the use of triangular lattice CARPC is unable to enhance the CPBG. It is almost twice as large as our previously reported result. Moreover, the CPBG of the square lattice CARPC could remain until an index contrast as low as 2.24:1. The result not only favors wideband CPBG applications for index contrast systems near 2.8:1, but also makes various optical applications that are dependent on CPBG possible for more widely index contrast systems.

Nonlinear optical properties of integrated GeSbS chalcogenide waveguides

Samuel Serna Otálvaro, Hongtao Lin, Carlos Alonso Ramos, Anupama Yadav, Xavier LE ROUX, Kathleen Richardson, Eric Cassan, Nicolas Dubeuil, Juejun Hu, and Laurent Vivien

Doc ID: 312707 Received 08 Nov 2017; Accepted 23 Jan 2018; Posted 24 Jan 2018  View: PDF

Abstract: In this paper, we report the experimental characterization of highly nonlinear GeSbS chalcogenide glass waveguides. We used a single-beam characterization protocol that accounts for the magnitude and sign of the real and imaginary parts of the third order nonlinear susceptibility of integrated Ge_{ }Sb_7S_{70} (GeSbS) chalcogenide glass waveguides in the near-infrared wavelength range at λ=1580 nm. We measured a waveguide nonlinear parameter of 7.0±0.7 W^{-1}m^{-1} which corresponds to a nonlinear refractive index of n_2= + (0.93± 0.08) × 10^{-18} m^{2}/W, comparable to that of silicon, but with a 80 times lower Two-Photon Absorption (TPA) coefficient β_{TPA}=(0.010±0.003) cm/GW, accompanied with linear propagation losses as low as 0.5 dB/cm. The outstanding linear and nonlinear properties of GeSbS, with a measured nonlinear figure of merit FOM_{TPA}=6.0±1.4 at λ=1580 nm, ultimately make it one of the most promising integrated platforms for the realization of nonlinear functionalities.

Highly efficient generation of arbitrary vector beams with tunable polarization, phase and amplitude

Sheng Liu, Shuxia Qi, yi zhang, Peng Li, Dongjing Wu, lei han, and Jianlin Zhao

Doc ID: 313394 Received 14 Nov 2017; Accepted 23 Jan 2018; Posted 24 Jan 2018  View: PDF

Abstract: We propose an efficient and robust method to generate tunable vector beams by employing a single phase-type spatial light modulator (SLM). With this method, a linearly polarized Gaussian beam can be converted into a vector beam with arbitrarily controllable polarization state, phase and amplitude. The energy loss during the conversion is greatly reduced and mainly dependents on the reflectivity of the SLM. We experimentally demonstrate that a conversion efficiency about 47% is achieved by using a SLM with reflectivity 62%. Several typical vector beams, including cylindrical vector beams, vector beams on higher-order Poincaré sphere, arbitrary vector beams attached phases and with tunable amplitude, are generated and verified experimentally. This method is also expected to create high-power vector beams and play important roles in optical fabrication and light trapping.

Towards mid-infrared kerr frequency comb generation in siliconcarbide microdisks engineered by lateral under-etching

David Allioux, Ali Belarouci, Darren Hudson, Eric Magi, Milan Sinobad, Guillaume Beaudin, Adrien Michon, Neetesh Singh, regis orobtchouk, and Christian Grillet

Doc ID: 310043 Received 14 Nov 2017; Accepted 22 Jan 2018; Posted 23 Jan 2018  View: PDF

Abstract: We report the fabrication and characterization of silicon carbide micro-disks on top of silicon pillars suited for applications from near to mid-infrared. We probe 10 μm diameter disks with different under-etchings depth, from 4 μm down to 1.4 μm, fabricated by isotropic plasma etching and can extract quality factors up to 8400 at telecom wavelength. Our geometry is suited to present high Q single mode operation. We experimentally demonstrate high order whispering gallery mode suppression while preserving the fundamental gallery mode and investigate the requirement for non-linear Kerr frequency comb generation on this platform.

Emerging Photoluminescence from Defective Vanadium Diselenide Nanosheets

Amir Ghobadi, Gamze Ghobadi, Ali Kemal Okyay, and Ekmel Ozbay

Doc ID: 315573 Received 12 Dec 2017; Accepted 21 Jan 2018; Posted 23 Jan 2018  View: PDF

Abstract: In this paper, for the first time in the literature, we demonstrate photoluminescence from two dimensional (2D) Vanadium Diselenide (VSe2) nanosheets (NSs). The preparation of these nanostructures are carried out with a combinational method based on nanosecond pulsed laser ablation (PLA) and chemical exfoliation. For this aim, VSe2 bulk is, firstly, ablated into nanoparticles (NPs) inside a water solution. Afterward, NPs are chemically exfoliated into NSs using Lithium intercalation via ultrasonic treatment. Although VSe2 is a semimetal in its bulk form, its nanostructures show photo-responsive behavior and it turns into a strongly luminescent material when it is separated into NSs. Based on the obtained results, the surface defects, induced during the PLA process, are the origin of this photoluminescence (PL) from NSs. Our findings illustrate that this new material can be a promising semiconductor for photovoltaic and light emitting diode (LED) applications.

Nonlinear Gallium Phosphide Nanoscale Photonics

Aude Martin, Sylvain Combrié, Alfredo De Rossi, Grégoire Beaudoin, ISABELLE SAGNES, and Fabrice Raineri

Doc ID: 312425 Received 03 Nov 2017; Accepted 20 Jan 2018; Posted 23 Jan 2018  View: PDF

Abstract: We introduce a nanoscale photonic platform based on Gallium Phosphide. Owing to the favorable material properties, peak power intensity levels of $50 GW/cm^2$ are safely reached in a suspended membrane. Consequently the field enhancement is exploited to a far greater extent to achieve efficient and strong light-matter interaction. As an example, parametric interactions are shown to reach a deeply nonlinear regime, revealing cascaded four wave mixing leading to comb generation and high order soliton dynamics.

Nonlinear Optics on Silicon Rich Nitride – A High Nonlinear Figure of Merit CMOS Platform

Dawn Tan, Kelvin Ooi, and Doris Ng

Doc ID: 309527 Received 24 Oct 2017; Accepted 20 Jan 2018; Posted 23 Jan 2018  View: PDF

Abstract: CMOS platforms with a high nonlinear figure of merit are highly sought after for high photon efficiencies, enabling functionalities not possible from purely linear effects and ease of integration with CMOS electronics. Silicon-based platforms have been prolific amongst the suite of advanced nonlinear optical signal processes demonstrated to date. These include crystalline silicon, amorphous silicon, Hydex glass and stoichiometric silicon nitride. Residing between stoichiometric silicon nitride and amorphous silicon in composition, silicon-rich nitride films of various formulations have emerged recently as promising nonlinear platforms for high nonlinear figure of merit nonlinear optics. Silicon-rich nitride films are compositionally engineered to create bandgaps that are sufficiently large to eliminate two photon absorption at the telecommunications wavelength while enabling much larger nonlinear waveguide parameters (5X-500X) than that in stoichiometric silicon nitride. This article reviews recent developments in the field of nonlinear optics using silicon-rich nitride platforms, as well as the outlook and future opportunities in this burgeoning field.

Influences of multiphoton absorption and free-carrier effects on frequency comb generation in normal dispersion silicon microresonators

mulong liu, Leiran Wang, Qibing Sun, siqi li, Zhiqiang Ge, zhizhou lu, Weiqiang Wang, Guoxi Wang, Wenfu Zhang, Xiaohong Hu, and wei zhao

Doc ID: 314400 Received 27 Nov 2017; Accepted 20 Jan 2018; Posted 23 Jan 2018  View: PDF

Abstract: We investigate frequency comb generation in normal dispersion silicon microresonators from near infrared to mid infrared wavelength range in the presence of multiphoton absorption and free-carrier effects. It is found that parametric oscillation is inhibited at telecom wavelength range resulting from strong two-photon absorption. On the contrary, beyond the wavelength of 2200 nm where three and four photon absorption are less detrimental, comb can be generated with moderate pump power or free-carriers are swept out by a positive-intrinsic-negative structure. In temporal domain, the generated combs correspond to flat-top pulses and the pulse duration can be easily controlled by varying the laser detuning. The reported comb generation process shows a high conversion efficiency compared with anomalous dispersion regime, which can guide and promote comb formation in materials with normal dispersion. As the comb spectra cover mid-infrared wavelength range, they can find applications in comb based radiofrequency photonic filters and mid-infrared spectroscopy.

Tuning second harmonic generation in AlGaAs nanodimers via non-radiative state optimization

Davide Rocco, Valerio Gili, Lavinia Ghirardini, Luca Carletti, Ivan Favero, Andrea Locatelli, Giuseppe Marino, Dragomir Neshev, Michele Celebrano, Marco Finazzi, Giuseppe Leo, and Costantino De Angelis

Doc ID: 312427 Received 06 Nov 2017; Accepted 19 Jan 2018; Posted 19 Jan 2018  View: PDF

Abstract: Dielectric nanocavities are emerging as a versatile and powerful tool for the linear and nonlinear manipulation of light at the nanoscale. In this work, we exploit the effective coupling of electric and toroidal modes in AlGaAs nanodimers to locally enhance both electric and magnetic fields while minimizing the optical scattering to optimize the efficiency of second harmonic generation in these optical nanoantennas with respect to the case of a single isolated nanodisk. We also demonstrate that a proper near-field coupling can provide further degrees of freedom to control the polarization state and the radiation diagram of the second harmonic field.

Dual-polarization wavelength conversion of 16-QAM signalsin a single silicon waveguide with lateral p-i-n diode

Francesco Da Ros, Andrzej Gajda, Erik Liebig, Edson Porto da Silva, Anna Peczek, Peter Girouard, Andreas Mai, Klaus Petermann, Lars Zimmermann, Michael Galili, and Leif Oxenlowe

Doc ID: 313029 Received 14 Nov 2017; Accepted 19 Jan 2018; Posted 19 Jan 2018  View: PDF

Abstract: A polarization-diversity loop with a silicon waveguide with lateral p-i-n diode as nonlinear medium is used to realize polarization insensitive four-wave mixing (FWM). Wavelength conversion of seven dual-polarization 16-quadrature amplitude modulation (QAM) signals at 16 GBd is demonstrated with an optical signal-to-noise ratio (OSNR) penalty below 0.7 dB. High-quality converted signals are generated thanks to the low polarization dependence (< 0.5 dB) and the high conversion efficiency (CE) achievable. The strong Kerr nonlinearity in silicon and the decrease of detrimental free-carrier absorption due to the reverse-biased p-i-n diode are key in ensuring the high CE levels.

Ultra-sensitive refractive index sensing based on plasmonic Fano resonances in a silver quadrumer system

HongJin Hu, zhang fanwei, guozhou li, Junyi Chen, Qiang Li, and Lijun Wu

Doc ID: 313402 Received 24 Nov 2017; Accepted 18 Jan 2018; Posted 19 Jan 2018  View: PDF

Abstract: A silver quadrumer consisting of four parallel aligned rectangular nanobars with three at the bottom and one at the top is proposed to provide two Fano resonances. These two resonances can be adjusted either simultaneously or independently simply by tuning the geometrical parameters. Due to the formation of the two resonances in a relatively short wavelength range, one of them can be spectrally squeezed to be very narrow which induces a very high Fig. of Merit (FoM=44). By decomposing the scattering spectrum into two bright modes and dark modes, the double Fano resonances are found to be originated from grouping the unit cells into two different groups. The evolution of the scattering spectrum with the central dimer position along the polarization direction suggests that the symmetry reducing induces the second Fano resonance and improves the FoM of the first one. By introducing one more nanobar into the quadrumer system, the FoM can approach the materials limit although the dip is relatively shallow. The ultrahigh FoM of the Fano resonance in the proposed quadrumer can provide ultra-sensitive refractive index sensing. Furthermore, the method for providing multiple independently-tunable Fano resonances can offer new solutions to designing plasmonic-related nanolasers, photocatalysis, biochemical sensors etc.

Tunable terahertz wave difference frequency generation in graphene/AlGaAs surface plasmon waveguide

Tao Chen, Liangling Wang, lijuan Chen, Jing Wang, Haikun Zhang, and Wei Xia

Doc ID: 313519 Received 14 Nov 2017; Accepted 18 Jan 2018; Posted 19 Jan 2018  View: PDF

Abstract: Graphene-based surface plasmon waveguides (SPW) show high confinement well beyond the diffraction limit at terahertz frequency. By combining graphene SPW and nonlinear material, we propose a novel graphene/AlGaAs SPW structure for terahertz wave difference frequency generation (DFG) under near-infrared pumps. The composite waveguide, which supports single-mode operation at terahertz frequency and guides two pumps by high-index-contrast AlGaAs/AlOx structure, can confine terahertz wave tightly and realize a good mode field overlap of three waves. The phase matching condition is satisfied via the artificial birefringent in AlGaAs/AlOx waveguide together with the tunability of graphene, and the phase-matching terahertz wave frequency varies from 4 to 7 THz when the Fermi energy level of graphene changes from 0.848 to 2.456 eV. Based on the coupled-mode theory, we investigate the power-normalized conversion efficiency for the tunable terahertz wave DFG process by using finite difference method under continous wave pumps, the tunable bandwidth can reach 2 THz with considerable conversion efficiency. To exploit the high peak power of pulses, we also discuss the optical pulse evolutions for pulse-pumped terahertz wave DFG process.

Hybrid silicon nonlinear photonics

Ming Li, Lin Zhang, Limin Tong, and Daoxin Dai

Doc ID: 312497 Received 15 Nov 2017; Accepted 18 Jan 2018; Posted 19 Jan 2018  View: PDF

Abstract: Nonlinear silicon photonics has shown its ability to generate, manipulate and detect optical signals on an ultra-compact chip with potential low cost. There are still barriers hindering its development due to essential material limitations. In this paper, hybrid structures with some specific materials developed for nonlinear silicon photonics are reviewed. The combination of silicon and the nonlinear materials takes advantage of both materials, which shows great potential for improving the performance and expanding the application of nonlinear silicon photonics.

Optical properties and applications for MoS2-Sb2Te3-MoS2 heterostructure materials

Wen Liu, Yanan Zhu, Mengli liu, Bo Wen, SHAOBO FANG, Hao Teng, Ming Lei, Li-Min Liu, and Zhiyi Wei

Doc ID: 313957 Received 20 Nov 2017; Accepted 18 Jan 2018; Posted 23 Jan 2018  View: PDF

Abstract: Two-dimensional (2D) materials with potential applications in photonic and optoelectronic devices have attracted increasing attention due to their unique structures and captivating properties. However, generation of stable high-energy ultrashort pulses requires further boosting 2D materials’ optical properties, such as higher damage threshold and larger modulation depth. Here we investigate a new type of heterostructure materials with controllable thickness and uniformity by employing the magnetron sputtering technique. Heterostructure materials with the van der Waals heterostructure consisting of MoS2 and Sb2Te3 are synthesized. The band gap, carrier mobility and carrier concentration of MoS2-Sb2Te3-MoS2 heterostructure materials are calculated theoretically. Using those materials as saturable absorbers (SAs), the applications in all-fiber lasers with Q-switching and mode locking states are demonstrated experimentally. The modulation depth and damage threshold of SAs are measured to be 64.17% and 14.13 J/cm2, respectively. Both theoretical and experimental results indicate that MoS2-Sb2Te3-MoS2 heterostructure materials have large modulation depth, and can resist high power during the generation of ultrashort pulses. The MoS2-Sb2Te3-MoS2 heterostructure materials have the advantages of the low cost, high reliability and suitability of mass production, and provide a promising solution for the development of 2D-material-based devices with desirable electronic and optoelectronic properties.

Switchable dual-wavelength Q-switching fiber laser using multi-layer black phosphorus as saturable absorber

Junmin Liu, yu chen, Ying Li, Han Zhang, Shuiqin Zheng, and Shixiang Xu

Doc ID: 313670 Received 20 Nov 2017; Accepted 17 Jan 2018; Posted 17 Jan 2018  View: PDF

Abstract: Black phosphorus (BP), with thickness-dependent direct energy band-gaps (0.3-2 eV), shows enhanced nonlinear optical response at near and mid-infrared wavelength. In this paper, we present experimentally multi-layer BP flakes coated on microfiber as a saturable absorber with modulation depth of 16% and saturable intensity of 6.8 MW/cm2. After inserting BCM into an Er-doped fiber ring laser, stable dual-wavelength Q-switching state with central wavelength of 1542.4 nm and 1543.2 nm (wavelength spacing as narrow as 0.8 nm) is obtained by the aid of two fiber Bragg gratings cascaded as coarse wavelength selector. Moreover, the single wavelength Q-switching operation at 1542.4 nm or 1543.2 nm is also realized, which can be switched each other flexibility just by adjusting intra-cavity birefringence. These results suggest that BP combined with the cascaded fiber gratings can provide a simple and feasible candidate for multi-wavelength fiber lasers.

High-speed and high-performance polarization-based quantum key distribution system without side channel effects caused by multiple lasers

Heasin Ko, Byung-Seok Choi, Joong-Seon Choe, Kap-Joong Kim, Jong-Hoi Kim, and Chun Ju Youn

Doc ID: 313600 Received 15 Nov 2017; Accepted 17 Jan 2018; Posted 19 Jan 2018  View: PDF

Abstract: Side channel effects such as temporal disparity and intensity fluctuation of photon pulses caused by random bit generation with multiple laser diodes in high-speed polarization-based BB84 quantum key distribution (QKD) systems can be eliminated by increasing DC bias current condition. However, background photons caused by the spontaneous emission process under high DC bias current degrade the performance of the QKD systems. In this study, we investigated, for the first time, the effects of spontaneously emitted photons on the system performance in a high-speed QKD system at a clock rate of 400 MHz. Also, we further show improvements of system performance without side channel effects by utilizing temporal filtering technique with real-time FPGA signal processing.

Optical Trapping of Single Quantum Dots for Cavity Quantum Electrodynamics

Pengfei Zhang, Gang Song, and Li Yu

Doc ID: 313145 Received 10 Nov 2017; Accepted 15 Jan 2018; Posted 17 Jan 2018  View: PDF

Abstract: We report here a nano-structure that traps single quantum dots for studying strong cavity-emitter coupling. The nano-structure is designed with two elliptical holes in a thin silver patch and a slot that connects the holes. This structure has two functionalities: 1) tweezers for optical trapping, and 2) a plasmonic resonant cavity for quantum electrodynamics. The electromagnetic response of the cavity is calculated by Finite-Difference Time-Domain (FDTD) simulations and the optical force is characterized based on the Maxwell’s stress tensor method. To be tweezers, this structure tends to trap quantum dots at the edges of its tips where light is significantly confined. To be a plasmonic cavity, its plasmonic resonant mode interacts strongly with the trapped quantum dots due to the enhanced electric field. Rabi splitting and anti-crossing phenomena are observed in the calculated scattering spectra, demonstrating that a strong-coupling regime has been achieved. The method present here provides a robust way to position a single quantum dot in a nano-cavity for investigating cavity quantum electrodynamics.

Relative intensity noise in high-speed hybrid square-rectangular lasers

Fu-Li Wang, Xiu-Wen Ma, Yong-Zhen Huang, Yue-De Yang, Jun-Yuan Han, and Jin-Long Xiao

Doc ID: 313591 Received 17 Nov 2017; Accepted 15 Jan 2018; Posted 17 Jan 2018  View: PDF

Abstract: The relative intensity noise (RIN) and high-speed modulation characteristics are investigated for an AlGaInAs/InP hybrid square-rectangular laser (HSRL) with square side length, rectangular length and width of 15, 300, and 2 μm, respectively. Single-mode operation with side mode suppression larger than 40 dB has been realized for the HSRL over wide variation of the injection currents. In addition, the HSRL exhibits a 3-dB modulation bandwidth of 15.5 GHz and a RIN nearly approaches standard quantum shot-noise limit 2hν/P = -164 dB/Hz at high bias currents due to the strong mode selection of the square microcavity. With the increasing of the DC bias current of the FP section, significantly enhanced modulation bandwidth and decreased RIN are observed. Furthermore, intrinsic parameters like resonance frequency, damping factor and the modified Schawlow-Townes linewidth are extracted from the noise spectra.

Bistable Lasing in Parity-Time Symmetric Coupled Fiber Rings

Sergey Smirnov, Maxim Makarenko, Sergey Suchkov, Dmitry Churkin, and Andrey Sukhorukov

Doc ID: 307530 Received 20 Sep 2017; Accepted 12 Jan 2018; Posted 12 Jan 2018  View: PDF

Abstract: We propose a parity-time (PT) symmetric fiber laser composed of two coupled ring cavities with gain and losses, which operates both in PT-symmetric and broken symmetry lasing depending on the static phase shifts. We perform analytical and numerical analysis by transfer matrix method taking into account gain saturation, and predict laser bistability in the PT-symmetric regime in contrast to a symmetry-broken single-mode operation. In the PT-broken regime, the generation power counter-intuitively increases with an increase of the cavity losses.

Mid-Infrared Silicon Photonic Waveguides and Devices

Yi Zou, Swapnajit Chakravarty, Chi-Jui Chung, Xiaochuan Xu, and Ray Chen

Doc ID: 306245 Received 06 Sep 2017; Accepted 10 Jan 2018; Posted 10 Jan 2018  View: PDF

Abstract: Silicon has been the material of choice of the photonics industry over the last decade due to its easy integration with silicon electronics as well as its optical transparency in the near-infrared and mid-infrared wavelengths. While considerations of micro- and nano-fabrication induced device parameter deviations and a higher than desirable propagation loss still serves as a bottleneck in many data communication applications on chip, applications as sensors do not require similar stringent controls. Photonic devices on chips are increasingly being demonstrated for chemical and biological sensing with performance metrics rivaling benchtop instruments and thus promising the potential of portable, handheld and wearable monitoring of various chemical and biological analytes. In this paper, we review recent advances in mid-infrared (MIR) silicon photonics research. We discuss the pros and cons of various platforms, the fabrication procedure for building such platforms, the benchmarks demonstrated so far, together with their applications. Novel device architectures and improved fabrication techniques have paved a viable way for realizing low-cost, high density, multi-function integrated devices in the MIR. These advances are expected to benefit several application domains in the years to come, including communication networks, sensing, and nonlinear systems.

X-ray absorption spectroscopy study of energy transport in foil targetsheated by PW laser pulses

Igor Skobelev, Sergey Ryazantsev, Denis Arich, Pavel Bratchenko, Anatoly Faenov, Tatiana Pikuz, Phill Durey, Leo Doehl, Damon Farley, Christopher Baird, Kate Lancaster, christopher murphy, Nicola Booth, Christopher Spindloe, Paul McKenna, Stephanie Hansen, James Colgan, Ryosuke Kodama, Nigel Woolsey, and Sergey Pikuz

Doc ID: 313362 Received 13 Nov 2017; Accepted 27 Dec 2017; Posted 03 Jan 2018  View: PDF

Abstract: Absorption x-ray spectroscopy is proposed as a method for studying the heating of a solid-density matter excited by secondary x-ray radiation from a relativistic laser-produced plasma. The method was developed and applied to experiments involving thin silicon foils irradiated by 0.5–1.5 ps duration ultrahigh contrast laser pulses at intensities between 0.5×1020 and 2.5×1020 W/cm2. The electron temperature of the material at the rear side of a target is estimated to be in the range of 140–300 eV. The diagnostic approach enables the diagnosis of warm dense matter states with low self-emissivity.

All-optical switching in Si photonic waveguides with epsilon-near-zero resonant cavity

Andres Neira, Gregory Wurtz, and Anatoly Zayats

Doc ID: 305271 Received 05 Sep 2017; Accepted 20 Dec 2017; Posted 22 Dec 2017  View: PDF

Abstract: Strong nonlinearity of plasmonic metamaterials can be designed near their effective plasma frequency in the epsilon near-zero (ENZ) regime. We explore the realization of an all-optical modulator based on the Au nonlinearity using an ENZ cavity formed by a few Au nanorods inside Si photonic waveguide. The resulting modulator has a robust performance with a modulation depth of about 30 dB/m and loss less than 0.8 dB at the switching energy below 600 fJ. The modulator provides a double advantage of high mode transmission and strong nonlinearity enhancement in the few nanorod-based design.

Single-Mode VCSEL for Pre-Emphasis PAM-4 transmission up to 64 Gbit/s over 100-300 m in OM4 MMF

Hsuan-Yun Kao, Cheng-Ting Tsai, Shan-Fong Leong, Chun-Yen Peng, Yu-Chieh Chi, Huai-Yung Wang, Hao-chung Kuo, Chao-Hsin Wu, Wood-Hi Cheng, and Gong-Ru Lin

Doc ID: 312994 Received 08 Nov 2017; Accepted 17 Dec 2017; Posted 22 Dec 2017  View: PDF

Abstract: A single-mode vertical cavity surface emitting laser (VCSEL) based data transmission is demonstrated, which enables 4-level pulse amplitude modulation (PAM-4) at 64 Gbit/s over 100-300 m in the OM4 multi-mode fiber (MMF). By optimizing the bias of the single-mode VCSEL with a differential resistance of 159 ohm the related electrical return loss of -5.7 dB is evaluated to provide an analog modulation bandwidth of 18.9 GHz. After pre-emphasizing waveform of the PAM-4 format, the PAM-4 data stream can be successfully delivered by the single-mode VCSEL at 64 Gbit/s under back-to-back and 100-m-long OM4 MMF conditions. Lengthening the transmission distance worsens the signal-to-noise ratio of PAM-4 data to the FEC criterion, as the waveform pre-emphasis of the PAM-4 data stream inevitably induces spectral power compensation from-low to high frequencies. Therefore, increasing the OM4 MMF distance from 200 to 300 m significantly reduces the peak-to-peak amplitude of data to suppress the SNR and reduce the transmission capacity from 52 to 48 Gbit/s.

Parity-time-symmetric whispering-gallery-mode nanoparticle sensor

Weijian Chen, Jing Zhang, Bo Peng, Sahin Ozdemir, Xudong Fan, and Lan Yang

Doc ID: 309078 Received 12 Oct 2017; Accepted 13 Dec 2017; Posted 15 Dec 2017  View: PDF

Abstract: We present a study of single nanoparticle detection using parity-time (PT)-symmetric whispering-gallery mode (WGM) resonators. Our theoretical model and numerical simulations show that with balanced gain and loss, the PT-symmetric WGM nanoparticle sensor, tailored to operate at the PT phase transition points (also called exceptional points), exhibits significant enhancement in frequency splitting when compared to a single WGM nanoparticle sensor subject to the same perturbation. The presence of gain in the PT-symmetric system leads to narrower linewidth, which helps to resolve smaller changes in the frequency splitting and improve detection limit of nanoparticle sensing. Furthermore, we also provide a general method for detecting multiple nanoparticles entering the mode volume of a PT-symmetric WGM sensor one by one. Our study shows the feasibility of PT-symmetric WGM resonators for ultrasensitive single nanoparticle and biomolecule sensing.

Surface-enhanced Raman scattering on dielectric microspheres with whispering gallery mode resonance

Steven Huang, Xuefeng Jiang, Bo Peng, Corey Janisch, Alexander Cocking, Sahin Ozdemir, Zhiwen Liu, and Lan Yang

Doc ID: 308983 Received 23 Oct 2017; Accepted 05 Dec 2017; Posted 06 Dec 2017  View: PDF

Abstract: Conventionally, metallic nanostructures are used for Surface-Enhanced Raman Spectroscopy (SERS), but recently there has been increasing interest in the enhancement of Raman scattering from dielectric substrates due to their improved stability and biocompatibility compared with metallic substrates. Here, we report the observation of enhanced Raman scattering from rhodamine 6G molecules coated on silica microspheres. We excite the Whispering-Gallery-Modes (WGMs) supported in the microspheres with tapered fiber coupler for efficient WGM excitation, and the Raman enhancement can be attributed to the WGM mechanism. Strong resonance enhancement in pump laser intensity and modified Raman emission from Purcell effect in the microsphere resonator are observed from experiment and compared with theoretical results. A total Raman enhancement factor of 1.4 × 10⁴ is observed, with contribution mostly from the enhancement in pump laser intensity. Our results show that with an efficient pumping scheme, dielectric microspheres are a viable alternative to metallic SERS substrates.

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