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Inverse-designed photonic fibers and metasurfaces for nonlinear frequency conversion

Alejandro Rodriguez, Chawin Sitawarin, Zin Lin, and Weiliang Jin

Doc ID: 313902 Received 22 Nov 2017; Accepted 20 Mar 2018; Posted 21 Mar 2018  View: PDF

Abstract: Typical photonic waveguides designed for nonlinear frequency conversion rely on intuitive and established principles, including index guiding and band-gap engineering, and are based on simple shapes with high degrees of symmetry. We show that recently developed inverse-design techniques can be applied to discover new kinds of microstructured fibers and metasurfaces designed to achieve large nonlinear frequency-conversion efficiencies. As a proof of principle, we demonstrate complex, wavelength-scale chalcogenide–glass fibers and gallium phosphide metasurfaces exhibiting some of the largest nonlinear conversion efficiencies predicted thus far. Such enhancements arise because, in addition to enabling a great degree of tunability in the choice of design wavelengths, these optimization tools ensure both frequency- and phase-matching in addition to large nonlinear overlap factors, potentially orders of magnitude larger than those obtained in hand-designed structures.

High-efficiency all dielectric transmission metasurface for linearly polarized light in the visible region

Liu Yang, dong wu, Yumin Liu, Chang Liu, Zenghui Xu, Li Hui, Zhongyuan Yu, Li Yu, and Han Ye

Doc ID: 319749 Received 15 Jan 2018; Accepted 20 Mar 2018; Posted 21 Mar 2018  View: PDF

Abstract: We propose and numerically investigate an efficient transmission-mode metasurface consisting of quasi-continuous trapezoid-shaped crystalline silicon nanoantennas on a quartz substrate which provides a linear phase gradient and realizes both full 2π phase shift and high transmission efficiency in the operating wavelength range from 740nm to 780nm. At the center wavelength around 751nm the total transmission efficiency is up to 88.0% and the section of the desired anomalous refraction is 80.4%. The anomalous refraction angle is 29.62° and larger refraction angle can be achieved by changing the period of the super cell. We demonstrate a refraction angle as large as 38.59° and the anomalous transmission efficiency reaches 76.6% at wavelength of 741nm. It is worth mentioning that, the structure is much more simple than conventional metasurfaces based on arrays of discrete nanoantennas which could effectively reduce the fabricating difficulty. Our research may pave the way for designing efficient all dielectric phase-gradient metasurfaces and applying in integrated optical devices for wavefront control.

Photonic spin Hall effect on the surface of anisotropic two-dimensional atomic crystals

Wenshuai Zhang, Weijie Wu, Shizhen Chen, Xiaohui Ling, Jin Zhang, Weixing Shu, Hailu Luo, and Shuangchun Wen

Doc ID: 318701 Received 28 Dec 2017; Accepted 18 Mar 2018; Posted 21 Mar 2018  View: PDF

Abstract: We examine the spin-orbit interaction of light and photonic spin Hall effect on the surface of anisotropic two-dimensional atomic crystals. As an example, the photonic spin Hall effect on the surface of black phosphorus is investigated. The photonic spin Hall effect manifests itself as the spin-dependent beam shifts in both transverse and in-plane directions. We demonstrate that the spin-dependent shifts are sensitive to the orientation of optical axis, doping concentration, and interband transitions. These results can be extensively extended to other anisotropic two-dimensional atomic crystals. By incorporating the quantum weak measurement techniques, the photonic spin Hall effect holds great promise for detecting the parameters of anisotropic two-dimensional atomic crystals.

Chip-scale broadband spectroscopic chemical sensing using integrated supercontinuum source in chalcogenide glass waveguide

Zhengqian Luo, Qingyang Du, Huikai Zhong, Yifei Zhang, Yizhong Huang, Tuanjie Du, Wei Zhang, Tian Gu, and Juejun Hu

Doc ID: 320562 Received 24 Jan 2018; Accepted 15 Mar 2018; Posted 16 Mar 2018  View: PDF

Abstract: On-chip spectroscopic sensors have attracted increasing attention for portable and field-deployable chemical detection applications. So far, these sensors largely rely on benchtop tunable lasers for spectroscopic interrogation. Large footprint and mechanical fragility of the sources, however, preclude compact sensing system integration. In this paper, we address the challenge through demonstrating, for the first time, a supercontinuum source integrated on-chip spectroscopic sensor, where we leverage nonlinear Ge22Sb18Se60 chalcogenide glass waveguides as a unified platform for both broadband supercontinuum generation and chemical detection. A home-built, palm-sized femtosecond laser centering at 1560 nm wavelength was used as the pumping source. Sensing capability of the system was validated through quantifying the optical absorption of chloroform solutions at 1695 nm. This work represents an important steptowards realizing a miniaturized spectroscopic sensing system based on photonic chips.

Circular Bragg lasers with radial PT symmetry: design and analysis with a coupled-mode approach

Ziyao Feng, Jingwen Ma, Zejie Yu, and Xiankai Sun

Doc ID: 312603 Received 03 Nov 2017; Accepted 14 Mar 2018; Posted 14 Mar 2018  View: PDF

Abstract: Parity–time (PT) symmetry has been demonstrated in the frame of classic optics. Its applications in laser science have resulted in unconventional control and manipulation of resonant modes. PT-symmetric periodic circular Bragg lasers were previously proposed. Analyses with a transfer-matrix method have shown their superior properties of reduced threshold and enhanced modal discrimination between the radial modes. However, the properties of the azimuthal modes were not analyzed, which restricts further development of circular Bragg lasers. Here, we adopt the coupled-mode theory to design and analyze chirped circular Bragg lasers with radial PT symmetry. The new structures possess more versatile modal control with further enhanced modal discrimination between the azimuthal modes. We also analyze azimuthally modulated circular Bragg lasers with radial PT symmetry, which are shown to achieve even higher modal discrimination.

Chirp control of fs-pulse scattering from drag-reducingsurface-relief gratings

Juliane Eggert, Bjorn Bourdon, Stefan Nolte, Jörg Rischmüller, and Mirco Imlau

Doc ID: 320238 Received 22 Jan 2018; Accepted 13 Mar 2018; Posted 14 Mar 2018  View: PDF

Abstract: The role of chirp on the light-matter interaction of femto- and picosecond laser pulses with functional structured surfaces is studied using drag reducing riblets as an example. The three-dimensional, periodic microstructure naturally gives rise to a mutual interplay of (i) reflection, (ii) scattering, and (iii) diffraction phenomena of incident coherent light. Furthermore, for femtosecond pulses, the structure induces (iv) an optical delay equivalent to a consecutive temporal delay of 0 fs in places of the pulse. These features enable to experimentally and numerically study the effect of tuning, both, pulse duration τ and spectral bandwidth Δω on the features of the wide-angle scattering pattern from the riblet structure. As a result, we discovered a significant break-down of fringes in the scattering pattern with decreasing pulse duration and/or increasing spectral bandwidth. This unique type of chirp control is straightforwardly explained and verified by numerical modeling considering the spectral and temporal interaction between different segments within the scattered, linearly chirped pulse andthe particular geometric features of the riblet structure. The visibility of the fringe pattern can be precisely adjusted, the off-state is achieved using τ < 0 fs or Δω > 2.85·10¹³ rad/s.

Tailoring active color rendering and multiband photodetection in vanadium dioxide based metamaterial absorber

Shichao Song, Ma Xiaoliang, Mingbo Pu, xiong li, ying guo, ping gao, and Xiangang Luo

Doc ID: 314139 Received 22 Nov 2017; Accepted 12 Mar 2018; Posted 14 Mar 2018  View: PDF

Abstract: Metamaterials have demonstrated exotic electromagnetic properties, which offers a good platform for realizing light absorption, photodetection, filtering, and so on. Yet, the broadband multi-functional metamaterial absorbers are restricted in cascaded structures. Here, the broadband multi-functional properties were realized by introducing vanadium dioxide into metamaterial absorber. Through the modified design and high efficient utilization of multiple resonant modes, both plasmonic tunable color filters and near-infrared photodetectors can be simultaneously achieved by this construction. Meanwhile, active color and photodetection wavelength in near infrared range can become tunable with the insulator-metallic transition of vanadium dioxide. Thus, the variations of rendering colors could correspondingly indicate the shifts of near-infrared photodetection wavelengths. This method theoretically confirms the feasibility of designing multifunctional devices via vanadium dioxide based metamaterial absorber, which hold great promise for future versatile utilization of multiple physical mechanisms to achieve numerous functionalities in a simple nanostructure or device.

Loss-Induced Control of Light Propagation Direction in Passive Linear Coupled Optical Cavities

Carlo Edoardo Campanella, Martino De Carlo, Antonello Cuccovillo, and Vittorio Passaro

Doc ID: 319440 Received 10 Jan 2018; Accepted 09 Mar 2018; Posted 13 Mar 2018  View: PDF

Abstract: Redirecting the flow of light on the basis of absorption/gain properties of the optical systems is of great interest in many research fields, ranging from optical routing to optical cloaking. In this paper we investigate the control of the direction of the light propagation through loss-induced absorption in passive linear coupled optical systems. The considered optical system consists in a mode splitting resonant cavity formed by coupling a Fabry–Pérot (FP) cavity with a ring resonator. The coalescence of the asymmetric resonances, generated through the mode splitting dynamics, is the spectral result of the PT symmetry breaking at the FP resonance wavelengths. For specific values of the FP overall loss, a predominant backward propagation in the FP ring resonator occurs. In fiber optics technology, this device shows an ability to invert the sense of the propagation of the light, quantified through the contrast ratio, in the order of 100. This value can be obtained by externally varying the FP loss coefficient, once fixed the other physical parameters of the FP ring resonator. Our results can open a new way toward novel high performance optical modulation and routing schemes.

Enhanced light extraction efficiency of tapered nanowire deep ultraviolet LED

Ronghui Lin, Sergio Galan, Haiding Sun, Yangrui Hu, Mohammed Sharizal, Bilal Janjua, Tien Khee Ng, Boon Ooi, and Xiaohang Li

Doc ID: 315785 Received 18 Dec 2017; Accepted 08 Mar 2018; Posted 08 Mar 2018  View: PDF

Abstract: Nanowire (NW) structure provides an alternative scheme for deep ultraviolet light emitting diodes (DUV-LEDs) that promises high material quality and better light extraction efficiency (LEE). In this report, we investigate the influence of the tapering angle of closely-packed AlGaN NWs, which is found to exist naturally in molecular beam epitaxy (MBE) grown NW structures, on the light extraction efficiency (LEE) of NW DUV-LED. It is observed that by increasing the tapering angle the vertical extraction is greatly enhanced for both transverse magnetic (TM) and transverse electric (TE) polarizations. Most notably, the vertical extraction of TM emission increased from 4.8% to 24.3%, which makes the LEE reasonably large to achieve high-performance DUV-LED. This is because the breaking of symmetry in the vertical direction changes the propagation of the light significantly to allow more coupling into radiation modes. Finally, we introduce errors to the NW positions to show the advantages of the tapered NW structures can be projected to random closely-packed NW arrays. The results obtained in this paper can provide guidelines for designing efficient NW DUV-LEDs.

An InP-based directly modulated monolithic integrated few-mode transmitter

Zhaosong Li, Dan Lu, Yiming He, Fangyuan Meng, Zhou liang, and Jiaoqing Pan

Doc ID: 320591 Received 26 Jan 2018; Accepted 07 Mar 2018; Posted 08 Mar 2018  View: PDF

Abstract: A monolithic integrated few-mode transmitter comprising of two directly modulated distributed feedback lasers and a multimode-interference-coupler-based mode converter-multiplexer was designed and demonstrated. The fundamental TE0 mode and first order TE1 mode generated from the transmitter were used to excite the LP01 and LP11 modes in a two-mode fiber. 2×10 Gbit/s direct modulation of the two mode-channels was successfully realized.

Broadband rhenium disulfide optical modulator for solid-state lasers

Xian-cui Su, Baitao Zhang, Yiran Wang, Guanbai He, Guoru Li, Na Lin, Kejian Yang, Jingliang He, and shande Liu

Doc ID: 324505 Received 19 Feb 2018; Accepted 07 Mar 2018; Posted 07 Mar 2018  View: PDF

Abstract: Rhenium disulfide (ReS₂), a member of group VII transition metal dichalcogenides (TMDs), has attracted increasing attention because of its unique distorted 1T structure and electronic and optical properties, which are much different from those of group VI TMDs (MoS₂, WS₂, MoSe₂, WSe₂, etc.). It has been proved that bulk ReS₂ behaves as a stack of electronically and vibrationally decoupled monolayer, which offers remarkable possibilities to prepare monolayer ReS₂ facilely and offers a novel platform to study photonic properties of TMDs. However, due to the large and layer-independent bandgap, the nonlinear optical properties of ReS₂ from visible to mid-infrared spectral range have not been investigated yet. Here, the band structure of ReS₂ with the introduction of defects is simulated by the ab initio method and the results indicate the bandgap can be reduced from 1.38 eV to 0.54 eV with the introduction of defects in a suitable range. In the experiment, using a bulk ReS₂ with suitable defects as the raw material, a few-layered broadband ReS₂ saturable absorber (SA) is prepared by liquid phase exfoliation method. Using the as-prepared ReS₂ SA, passively Q-switched solid-state lasers at wavelength of 0.64, 1.064, and 1.991 μm are investigated systematically. Moreover, with cavity design, a femtosecond passively mode-locked laser at 1.06 μm is successfully realized based on the as-prepared ReS₂ SA for the first time. The results present a promising alternative for rare broadband optical modulator and indicate the potential of ReS₂ in generating Q-switched and mode-locked pulsed lasers. It is further anticipated that this work may be helpful for the design of two-dimensional optoelectronic devices with variable bandgaps.

Optically spatial information selection with hybridly polarized beam in atomic vapor

Jinwen Wang, Xin Yang, Yunke Li, yun chen, Mingtao Cao, dong wei, Hong Gao, and fuli li

Doc ID: 319700 Received 12 Jan 2018; Accepted 06 Mar 2018; Posted 07 Mar 2018  View: PDF

Abstract: Vector beams with spatially variant polarization are attracted much attentions in recent years, with potential applications in both classical optics and quantum optics. In this work, we study a polarization selection of spatial intensity distribution by utilizing hybridly polarized beam as coupling beam and circularly polarized beam as probe beam in $^{87}$Rb atom vapor. We experimentally observe that the spatial intensity distribution of probe beam after passing through atoms can be modulated by the hybridly polarized beam due to optical pumping effect. Then the information loaded in the probe beam can be designedly filtrated by atomic system with high extinction ratio. A detailed process of optical pumping effect in our configurations and the corresponding absorption spectrums are present to interpret our experimental results. The results can be used for the spatial optical information locally extracted based on atomic system which has potential application in quantum communication and computation.

A multifunctional metasurface: from extraordinary optical transmission to extraordinary optical diffraction in a single structure

Zi-Lan Deng, Yao-Yu Cao, Xiangping Li, and Guo Ping Wang

Doc ID: 315544 Received 12 Dec 2017; Accepted 04 Mar 2018; Posted 07 Mar 2018  View: PDF

Abstract: We show that, a metasurface composed of subwavelength metallic slit array embedded in an asymmetric dielectric environment can exhibit either extraordinary optical transmission (EOT) or extraordinary optical diffraction (EOD). The cascaded refractive indices of the dielectrics can leverage multiple decaying passages into variant subsections with different diffraction order combinations according to the diffraction order chart in the k-vector space, providing a flexible mean to tailor resonance decaying pathways of the metallic slit cavity mode by changing the wavevector of the incident light. As a result, either the 0th transmission or -1st reflection efficiencies can be enhanced to near-unity by the excitation of the localized slit cavity mode, leading to either EOT or EOD in a single structure, depending on the illumination angle. Based on this appealing feature, a multifunctional metasurface that can switch its functionality between transmission filter, mirror and off-axis lens is demonstrated. Our findings provide a convenient way to construct multifunctional miniaturized optical components on a single planar device.

Control of soft X-ray high harmonic spectrum by using two-color laser pulses

Cheng Jin and Chii Dong Lin

Doc ID: 321155 Received 01 Feb 2018; Accepted 01 Mar 2018; Posted 05 Mar 2018  View: PDF

Abstract: We demonstrate the suppression of soft X-ray high harmonics generated by two-color laser pulses interacting with Ne gas in a gas cell. We show that harmonic suppression can occur at the proper combination of the propagation distance and gas pressure. The physical mechanism behind is the phase mismatch between "short"-trajectory harmonics generated at the early and the later times through the interplay of geometric phase, dispersion and plasma effects. In addition, we demonstrate that the position and depth of harmonic suppression can be tuned by increasing the gas pressure. Furthermore, the suppression can be extended to other laser focusing geometries by properly scaling macroscopic parameters. Our investigation reveals a simple and novel experimental scheme purely relying on the phase mismatch for selectively controlling soft X-ray tabletop light sources without adopting the fifilters for applications.

Sensitivity Enhanced Surface Plasmon Resonance Sensor Utilizing a Thin Overlayer of Tungsten Disulfide (WS2) Nanosheets

Hao Wang, zhang hui, Jiangli Dong, Shiqi Hu, Wenguo Zhu, Wentao Qiu, Huihui Lu, Jianhui Yu, Heyuan Guan, She Gao, Zhaohui Li, Weiping Liu, Miao He, Jun Zhang, Zhe Chen, and Yunhan Luo

Doc ID: 314480 Received 14 Dec 2017; Accepted 28 Feb 2018; Posted 05 Mar 2018  View: PDF

Abstract: Tungsten Disulfide (WS2), as a representative layered transition metal dichalcogenide (TMDC) material, possess important potential for applications in highly sensitive sensors. Here, a sensitivity enhanced surface plasmon resonance (SPR) sensor with the metal film modified by a thin overlayer of WS2 nanosheets is proposed and investigated. The sensing sensitivity is related to the thicknesses of WS2 overlayer which can be tailored by coating WS2 ethanol suspension with different concentrations or the number of times of repeated post-coating. Benefitting from its large surface area and high refractive index, the WS2 nanosheet overlayer coated on the gold film significantly improved the sensing sensitivity. The highest sensitivity (up to 2459.3 nm/RIU) is achieved at coating WS2 suspension one time in experiment. Compared to the case of without WS2 overlayer, this result shows a sensitivity enhancement of 26.6%. The influence of WS2 nanosheet overlayer on the sensing performance improvement is analyzed and discussed. Moreover, the proposed WS2-SPR sensor has a linear correlation coefficient of 99.76% in refractive index range of 1.333 RIU to 1.360 RIU. Besides sensitivity enhancement, the WS2 nanosheet overlayer is able to take additional advantages, such as protection of metal film from oxidation, tunability of the resonance wavelength region, biocompatibility, capability of vapor and gas sensing.

Spectrally-flat supercontinuum generation in a holmium-doped ZBLAN fiber with record power ratio beyond 3 μm

Linyong Yang, Bin Zhang, Ke Yin, Tianyi Wu, Yijun Zhao, and Jing Hou

Doc ID: 320378 Received 24 Jan 2018; Accepted 26 Feb 2018; Posted 28 Feb 2018  View: PDF

Abstract: A spectrally-flat mid-infrared supercontinuum (MIR-SC) spanning 2.8 to 3.9 μm with maximum output power of 411 mW was generated in a holmium-doped ZBLAN fiber amplifier (HDZFA). A broadband fiber-based SC covering 2.4-3.2 μm region was designed to seed the amplifier. Benefited from the broadband seed laser, the obtained SC had high spectral flatness with a 3-dB bandwidth of 770 nm covering 2.93-3.70 μm region. In particular, spectral integral showed that the SC power beyond 3 μm was 372 mW, i.e., a power ratio of 90.6 % of the total power. This Letter, to the best of our knowledge, not only demonstrates the first spectrally-flat MIR-SC directly generated in fluoride fiber amplifiers, but also reports the highest power ratio beyond 3 μm obtained in rare-earth-doped fluoride fiber by now.

Configuration dependent output characteristics with Fabry-Perot and random lasers from dye-doped LCs within glass cells

Ja-Hon Lin, YI-HAN LI, Sheng Lin, and Bich-Hanh Nguyen

Doc ID: 320884 Received 29 Jan 2018; Accepted 25 Feb 2018; Posted 26 Feb 2018  View: PDF

Abstract: We demonstrate the abundant dynamics of dye-doped liquid crystal (DD-LC) lasers through the variation of geometric shape and rubbing polyimide (PI) of glass cells. Not only the operation state, i.e., Fabry-Perot lasers (FPLs) or random lasers (RLs), were manipulated by using a parallel or wedge cell, but also the output polarization, i.e., linearly-polarized or un-polarized DD-LC lasers, were determined by the rubbing PI on an output glass plate. From the α-stable distribution, the distinctive operation state of the different configurations of the DDLC laser can be quantitatively distinguished to reveal the Gaussian and Levy distributions of the FPLs and RLs, respectively. The obviously different output characteristics are attributed to the multiplelight scattering within the LC mixtures at the output plate of the DD-LC lasers and were quantifified by the transport mean free path through the measurement of the coherent back scattering technique. An un-polarizedRL, outputted from a wedge cell without PI rubbing, revealed relatively low spatial coherence from interference patterns through Young's double-slit experiment and showed low contrast monochromatic speckle patterns ofabout 0.039

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.

20. 1 Gbit/s Tricolor R/G/B Laser Diode based Bi-directional Signal Remodulation Visible Light Communication System

Chi Wai Chow, L. Y. Wei, Chien-Hung Yeh, and C.-W. Hsu

Doc ID: 314932 Received 04 Dec 2017; Accepted 05 Feb 2018; Posted 28 Feb 2018  View: PDF

Abstract: We propose and experimentally demonstrate a recorded bi-directional 20. 1-Gbit/s tricolor R/G/B laser diode (LD) based visible-light-communication (VLC) system supporting signal remodulation. In the signal remodulation system, LD source is not needed at the client side. The client reuses the downstream signal sent from the central office (CO) and re-modulates it to produce the upstream signal. As the LD sources are located at the CO, the laser wavelength and temperature managements at the cost-sensitive client side are not needed. This is the first demonstration, up to the our knowledge, of a > 20 Gbit/s data rate tricolor R/G/B VLC signal transmission supporting upstream remodulation.

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.

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.

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.

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.

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.

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.

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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