分类： 光学 >> 量子光学 提交时间： 2023-02-20
摘要： An ultra-compact one-dimensional topological photonic crystal (1D-TPC) is designed in a single mode silicon bus-waveguide to generate Fano resonance lineshape. The Fano resonance comes from the interference between the discrete topological boundary state of the 1D-TPC and the continuum high-order leaky mode of the bus-waveguide. Standalone asymmetric Fano resonance lineshapes are obtained experimentally in the waveguide transmission spectrum with a maximum extinction ratio of 33 dB and a slope ratio of 10 dB/nm over a broadband flat background.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Strongly enhanced third-harmonic generation (THG) by the topological localization of an edge mode in a Su-Schrieffer-Heeger (SSH) chain of silicon photonic crystal nanocavities is demonstrated. The edge mode of the nanocavity chain not only naturally inherits resonant properties of the single nanocavity, but also exhibits the topological feature with mode robustness extending well beyond individual nanocavity. By engineering the SSH nanocavities with alternating strong and weak coupling strengths on a silicon slab, we observe the edge mode formation that entails a THG signal with three orders of magnitude enhancement compared with that in a trivial SSH structure. Our results indicate that the photonic crystal nanocavity chain could provide a promising on-chip platform for topology-driven nonlinear photonics.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： A topologically protected ring-resonator formed in valley photonic crystals is proposed and fabricated on a silicon slab. The unidirectional transmission and robustness against structure defects of its resonant modes are illustrated. Coupled with topological waveguides, the topological ring is functioned as notch and channel-drop filters. The work opens up a new avenue for developing advanced chip-integrated photonic circuits with attributes of topological photonics.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
Jing Wang
Nannan Han
Zheng-Dong Luo
Mingwen Zhang
Xiaoqing Chen
Yan Liu
Yue Hao
Jianlin Zhao
Xuetao Gan
摘要： Electrical tuning of second-order nonlinearity in optical materials is attractive to strengthen and expand the functionalities of nonlinear optical technologies, though its implementation remains elusive. Here, we report the electrically tunable second-order nonlinearity in atomically thin ReS2 flakes benefiting from their distorted 1T crystal structure and interlayer charge transfer. Enabled by the efficient electrostatic control of the few-atomic-layer ReS2, we show that second harmonic generation (SHG) can be induced in odd-number-layered ReS2 flakes which are centrosymmetric and thus without intrinsic SHG. Moreover, the SHG can be precisely modulated by the electric field, reversibly switching from almost zero to an amplitude more than one order of magnitude stronger than that of the monolayer MoS2. For the even-number-layered ReS2 flakes with the intrinsic SHG, the external electric field could be leveraged to enhance the SHG. We further perform the first-principles calculations which suggest that the modification of in-plane second-order hyperpolarizability by the redistributed interlayer-transferring charges in the distorted 1T crystal structure underlies the electrically tunable SHG in ReS2. With its active SHG tunability while using the facile electrostatic control, our work may further expand the nonlinear optoelectronic functions of two-dimensional materials for developing electrically controllable nonlinear optoelectronic devices.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
Xutao Zhang
Ruixuan Yi
Nikita Gagrani
Ziyuan Li
Fanlu Zhang
Xuetao Gan
Xiaomei Yao
Xiaoming Yuan
Naiyin Wang
Jianlin Zhao
Pingping Chen
Wei Lu
Lan Fu
Hark Hoe Tan
Chennupati Jagadish
摘要： We present single-mode nanowire (NW) lasers with ultralow threshold in the near-infrared spectral range. To ensure the single-mode operation, the NW diameter and length are reduced specifically to minimize the longitudinal and transverse modes of the NW cavity. Increased optical losses and reduced gain volume by the dimension reduction are compensated by excellent NW morphology and InGaAs/GaAs multi-quantum disks. At 5 K, a threshold low as 1.6 {\mu}J/cm2 per pulse is achieved with a resulting quality factor exceeding 6400. By further passivating the NW with an AlGaAs shell to suppress surface non-radiative recombination, single-mode lasing operation is obtained with a threshold of only 48 {\mu}J/cm2 per pulse at room temperature with a high characteristic temperature of 223 K and power output of ~ 0.9 {\mu}W. These single-mode, ultralow threshold, high power output NW lasers are promising for the development of near-infrared nanoscale coherent light sources for integrated photonic circuits, sensing, and spectroscopy.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： On chip exciting electric modes in individual plasmonic nanostructures are realized widely; nevertheless, the excitation of their magnetic counterparts is seldom reported. Here, we propose a highly efficient on chip excitation approach of the magnetic dipole mode of an individual split ring resonator (SRR) by integrating it onto a photonic crystal nanocavity (PCNC). A high excitation efficiency of up to 58% is realized through the resonant coupling between the modes of the SRR and PCNC. A further fine adjustment of the excited magnetic dipole mode is demonstrated by tuning the relative position and twist angle between the SRR and PCNC. Finally, a structure with a photonic crystal waveguide side coupled with the hybrid SRR PCNC is illustrated, which could excite the magnetic dipole mode with an in plane coupling geometry and potentially facilitate the future device application. Our result may open a way for developing chip integrated photonic devices employing a magnetic field component in the optical field.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
Ruijuan Tian
Xuetao Gan
Chen Li
Xiaoqing Chen
Siqi Hu
Linpeng Gu
Dries Van Thourhout
Andres Castellanos-Gomez
Zhipei Sun
Jianlin Zhao
摘要： Two-dimensional materials are attractive for constructing high-performance photonic chip-integrated photodetectors because of their remarkable electronic and optical properties and dangling-bond-free surfaces. However, the reported chip-integrated two-dimensional material photodetectors were mainly implemented with the configuration of metal-semiconductor-metal, suffering from high dark currents and low responsivities at high operation speed. Here, we report a van der Waals PN heterojunction photodetector, composed of p-type black phosphorous and n-type molybdenum telluride, integrated on a silicon nitride waveguide. The built-in electric field of the PN heterojunction significantly suppresses the dark current and improves the responsivity. Under a bias of 1 V pointing from n-type molybdenum telluride to p-type black phosphorous, the dark current is lower than 7 nA, which is more than two orders of magnitude lower than those reported in other waveguide-integrated black phosphorus photodetectors. An intrinsic responsivity up to 577 mA/W is obtained. Remarkably, the van der Waals PN heterojunction is tunable by the electrostatic doping to further engineer its rectification and improve the photodetection, enabling an increased responsivity of 709 mA/W. Besides, the heterojunction photodetector exhibits a response bandwidth of ~1.0 GHz and a uniform photodetection over a wide spectral range, as experimentally measured from 1500 to 1630 nm. The demonstrated chip-integrated van der Waals PN heterojunction photodetector with low dark current, high responsivity and fast response has great potentials to develop high-performance on-chip photodetectors for various photonic integrated circuits based on silicon, lithium niobate, polymer, etc.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
Qiao Zhang
Yingke Ji
Siqi Hu
Zhiwen Li
Chen Li
Linpeng Gu
Ruijuan Tian
Jiachen Zhang
Liang Fang
Bijun Zhao
Jianlin Zhao
Xuetao Gan
摘要： We report a high-responsive hot-electron photodetector based on the integration of an Au-MoS$_2$ junction with a silicon nitride microring resonator (MRR) for detecting telecom-band light. The coupling of the evanescent field of the silicon nitride MRR with the Au-MoS$_2$ Schottky junction region enhances the hot-electron injection efficiency. The device exhibits a high responsivity of 154.6 mA W-1 at the wavelength of 1516 nm, and the moderately uniform responsivities are obtained over the wavelength range of 1500 nm-1630 nm. This MRR-enhanced MoS2 hot-electron photodetector offers possibilities for integrated optoelectronic systems.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Missing second-order nonlinearity in centrosymmetric graphene overshadows its intriguing optical attribute. Here, we report redox-governed charge doping could effectively break the centrosymmetry of bilayer graphene (BLG), enabling a strong second harmonic generation (SHG) with a strength close to that of the well-known monolayer MoS2. Verified from control experiments with in situ electrical current annealing and electrically gate-controlled SHG, the required centrosymmetry breaking of the emerging SHG arises from the charge-doping on the bottom layer of BLG by the oxygen/water redox couple. Our results not only reveal that charge doping is an effective way to break the inversion symmetry of BLG despite its strong interlayer coupling but also indicate that SHG spectroscopy is a valid technique to probe molecular doping on two-dimensional materials.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Silicon nitride (SiN) photonics platform has attributes of ultra-low linear and nonlinear propagation losses and CMOS-compatible fabrication process, promising large-scale multifunctional photonic circuits. However, the centrosymmetric nature of SiN inhibits second-order nonlinear optical responses in its photonics platform, which is desirable for developing efficient nonlinear active devices. Here, we demonstrate high-efficiency second-order nonlinear processes in SiN photonics platform by integrating a few-layer GaSe flake on a SiN microring resonator. With the pump of microwatts continuous-wave lasers, second-harmonic generation and sum-frequency generation with the conversion efficiencies of 849%/W and 123%/W, respectively, are achieved, which benefit from the ultrahigh second-order nonlinear susceptibility of GaSe, resonance enhanced GaSe-light interaction, and phase-matching condition satisfied by the mode engineering. Combining with the easy integration, the GaSe-assisted high-efficiency second-order nonlinear processes offer a new route to enriching already strong functionality of SiN photonics platform in nonlinear optics.
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