Browsing by Author "Li, Zhitong"
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Item Effective Modal Volume in Nanoscale Photonic and Plasmonic Near-Infrared Resonant Cavities(MDPI AG) Li, Xi; Smalley, J. S.; Li, Zhitong; Gu, Qing; 0000-0003-2707-4969 (Li, X); 0000-0003-3855-3690 (Gu, Q); Li, Xi; Li, Zhitong; Gu, QingWe survey expressions of the effective modal volume, Veff, commonly used in the literature for nanoscale photonic and plasmonic cavities. We apply different expressions of V_{eff} to several canonical cavities designed for nanoscale near-infrared light sources, including metallo-dielectric and coaxial geometries. We develop a metric for quantifying the robustness of different V_{eff} expressions to the different cavities and materials studied. We conclude that no single expression for V_{eff} is universally applicable. Several expressions yield nearly identical results for cavities with well-confined photonic-type modes. For cavities with poor confinement and a low quality factor, however, expressions using the proper normalization method need to be implemented to adequately describe the diverging behavior of their effective modal volume. The results serve as a practical guideline for mode analysis of nanoscale optical cavities, which show promise for future sensing, communication, and computing platforms.Item Nanoimprinted Perovskite Metasurface for Enhanced Photoluminescence(Optical Soc Amer, 2018-11-05) Wang, Honglei; Liu, Shih-Chia; Balachandran, Balasubramaniam; Moon, Jiyoung; Haroldson, Ross; Li, Zhitong; Ishteev, Artur; Gu, Qing; Zhou, Weidong; Zakhidov, Anvar A.; Hu, Wenchuang (Walter); 0000 0003 5287 0481 (Zakhidov, AA); 0000-0003-3983-2229 (Zakhidov, AA); Wang, Honglei; Balachandran, Balasubramaniam; Moon, Jiyoung; Haroldson, Ross; Li, Zhitong; Gu, Qing; Zakhidov, Anvar A.; Hu, Wenchuang (Walter)Recently, solution-processed hybrid halide perovskite has emerged as promising materials for advanced optoelectronic devices such as photovoltaics, photodetectors, light emitting diodes and lasers. In the mean time, all-dielectric metasurfaces with high-index materials have attracted attention due to their low-loss and high-efficient optical resonances. Because of its tunable by composition band gap in the visible frequencies, organolead halide perovskite could serve as a powerful platform for realizing high-index, low-loss metasurfaces. However, direct patterning of perovskite by lithography-based technique is not feasible due to material instability under moisture. Here we report novel organolead halide perovskite metasurfaces created by the cost-effective thermal nanoimprint technology. The nanoimprinted perovskite metasurface showed improved surface morphology and enhanced optical absorption properties. Significantly enhanced optical emission with an eight-fold enhancement in photoluminescence (PL) intensity was observed under room temperature. Temperature-dependent PL of perovskite nanograting metasurface was also investigated. Based on our results, we believe that thermal nanoimprint is a simple and cost-effective technique to fabricate perovskite-based metasurfaces, which could have broad impact on optoelectronic and photonic applications.Item Perovskite Nanophotonic Devices and Topological Photonic Devices(2021-05-01T05:00:00.000Z) Li, Zhitong; Gu, Qing; Minary, Majid; Zhang, Chuanwei; Lee, Jeong-Bong; Zakhidov, Anvar A.Solution processed organic-inorganic lead halide perovskites have rapidly emerged as a promising gain material for development of the next generation of nanophotonic device ranging from nanolasers, nano LEDs, and solar cells. Here, continuous-wave operation of MAPbI3 perovskite nanolaser is achieved at room temperature with ultralow threshold, which is enabled by thermal nanoimprint lithography that directly patterns perovskite into laser cavities and improves perovskite’s emission characteristics. In the meantime, hyperbolic metamaterials and metasurfaces (HMMs), a special class of anisotropic media, has drawn tremendous research attention recently owing to its remarkable ability to manipulate electromagnetic waves at the subwavelength scale. However, the inevitable metal loss hinders the development of HMMs. Here, a luminescent perovskite HMM operating at 760 nm is achieved using alternating layers of MAPbI3 perovskite and Au, where the loss in Au is maximally compensated by MAPbI3. Simultaneously, topological photonics is a rapidly emerging field, aiming to apply topological physics in photonic systems. The topological protected photonic edge mode is immune to the system disorders and imperfections. However, all photonic edge modes reported in the pioneering works are from lattice systems. Here, a topological band theory is developed in continuous HMM through a nonHermitian Hamiltonian formulated Maxwell’s equations. Two types of edge mode can be induced by including gyromagnetic and chiral effect in HMM and can be numerically observed. Finally, a topological micro ring laser array that possesses edge mode lasing is designed and experimentally achieved on the III-V semiconductor platform.Item Room Temperature Operation of Directly Patterned Perovskite Distributed Feedback Light Source under Continuous-Wave Optical Pumping(Institute of Electrical and Electronics Engineers Inc.) Gharajeh, Abouzar; Haroldson, Ross; Li, Zhitong; Moon, Jiyoung; Balachandran, Balasubramaniam; Hu, Wenchuang (Walter); Zakhidov, Anvar A.; Gu, Qing; 0000 0003 5287 0481 (Zakhidov, AA); 0000-0003-3983-2229 (Zakhidov, AA); 0000-0003-3855-3690 (Gu, Q); Gharajeh, Abouzar; Haroldson, Ross; Li, Zhitong; Moon, Jiyoung; Balachandran, Balasubramaniam; Hu, Wenchuang (Walter); Zakhidov, Anvar A.; Gu, QingWe report the first directly patterned perovskite distributed feedback (DFB) resonator with a narrow amplified spontaneous emission (ASE) at pump powers as low as 0.1W/cm², under continuous-wave (CW) optical pumping condition at room temperature.