Browsing by Author "Wang, Chun-Yuan"

Now showing 1 - 16 of 16

All-Color Plasmonic Nanolasers with Ultralow Thresholds: Autotuning Mechanism for Single-Mode Lasing
(2014-08-01)
Lu, Yu-Jung
;
Wang, Chun-Yuan
;
Kim, Jisun
;
Chen, Hung-Ying
;
Lu, Ming-Yen
We report on the first demonstration of broadband tunable, single-mode plasmonic nanolasers (spasers) emitting in the full visible spectrum. These nanolasers are based on a single metal oxide semiconductor nanostructure platform comprising of InGaN/GaN semiconductor nanorods supported on an Al2O3-capped epitaxial Ag film. In particular, all-color lasing in subdiffraction plasmonic resonators is achieved via a novel mechanism based on a property of weak size dependence inherent in spasers. Moreover, we have successfully reduced the continuous-wave (CW) lasing thresholds to ultrasmall values for all three primary colors and have clearly demonstrated the possibility of "thresholdless" lasing for the blue plasmonic nanolaser.
All-Color Plasmonic Nanolasers with Ultralow Thresholds: Autotuning Mechanism for Single-Mode Lasing
(2014-08-01)
Lu, Yu-Jung
;
Wang, Chun-Yuan
;
Kim, Jisun
;
Chen, Hung-Ying
;
Lu, Ming-Yen
We report on the first demonstration of broadband tunable, single-mode plasmonic nanolasers (spasers) emitting in the full visible spectrum. These nanolasers are based on a single metal oxide semiconductor nanostructure platform comprising of InGaN/GaN semiconductor nanorods supported on an Al2O3-capped epitaxial Ag film. In particular, all-color lasing in subdiffraction plasmonic resonators is achieved via a novel mechanism based on a property of weak size dependence inherent in spasers. Moreover, we have successfully reduced the continuous-wave (CW) lasing thresholds to ultrasmall values for all three primary colors and have clearly demonstrated the possibility of "thresholdless" lasing for the blue plasmonic nanolaser.
Broadband Multifunctional Plasmonic Logic Gates
(2018-07-04)
Sang, Yungang
;
Wu, Xiaojia
;
Raja, Soniya S.
;
Wang, Chun-Yuan
;
Li, Haozhi
Plasmonic logic gates provide a promising platform to realize diffraction-unlimited all-optical logic circuits. However, previous plasmonic logic gates suffer from narrow bandwidth and high loss. Here, broadband plasmonic logic gates are proposed and demonstrated using a unique design based on curved silver gratings. These logic gates can maintain a high intensity contrast ratio (29 dB) under front optical illumination. And, the broadband feature is achieved due to the feature of zero optical path difference from different positions of the curved grating to the output port. All the seven fundamental logic gates are demonstrated. In addition, different types of logic gates can be realized using the same device configuration. The possibility of multifunctionality makes these logic gates easy for device fabrication and system integration.
Dielectric impact on exciton binding energy and quasiparticle bandgap in monolayer WS2 and WSe2
(2019-04-01)
Hsu, Wei-Ting
;
Quan, Jiamin
;
Wang, Chun-Yuan
;
Lu, Li-Syuan
;
Campbell, Marshall
Excitons, bound electron-hole pairs in a 2D plane, dominate the optical properties of monolayer transition metal dichalcogenides (TMDs). A large exciton binding energy on the order of 0.5 eV was theoretically predicted and experimentally determined recently. These ultrastable excitons thus open an avenue to explore the exciton physics such as Bose-Einstein condensation and superfluidity at room temperature (Kasprzak et al 2006 Nature 443 409; Plumhof et al 2014 Nat. Mater. 13 247; Fogler et al 2014 Nat. Commun. 5 4555; Jiang and John 2014 Sci. Rep. 4 7432). Recent experiments further demonstrated the concept of Coulomb engineering via dielectric environments based on either solutions or few-layer graphene. However, the conducting nature of these dielectrics can lead to quenching of optical transitions. Thus, in order to utilize 'dielectric tuning' of the exciton binding energy and quasiparticle band gaps, one must use insulating dielectrics. Here, we investigate the impact of insulating dielectric environments on the exciton binding energy of monolayer WS2 and WSe2 by exciton Rydberg spectroscopy, in which the dielectric environment is systematically varied from kappa= 1.49 to 3.82. We found that, with increasing kappa value, the exciton binding energy and quasiparticle bandgap exhibit significant reductions. Quantitatively, our result follows the prediction of nonlocally-screened Keldysh potential very well. The fitted 2D polarizability, Chi(2D), agrees rather well with previous density function theory calculations. Their close agreement validates the nonlocally-screened Keldysh model which can be used to quantitatively predict the exciton binding energy for monolayer TMDs (and possibly other 2D materials) in different dielectric environments. Such a predictive model will play an important role for the design of van der Waals heterostructures and TMD-based optoelectronic devices.
Diffraction-Unlimited Plasmonic Nanolaser
(2015-01-01)
Lu, Yu-Jung
;
Kim, Jisun
;
Chen, Hung-Ying
;
Wu, Chihhui
;
Dabidian, Nima
Efficient single photon sources based on nanodiamonds on a plasmonic platform
(2014)
Chen, Yen-Chun
;
Tsai, Cheng-Yen
;
Wang, Chun-Yuan
;
Gwo, Shangir
;
Wen-HaoChang
We report on an efficient room-temperature source of single photons based on single nitrogen-vacancy centers in nanodiamonds (NDs) placing on a large-area plasmonic platform formed by crystalline gold flakes covered with a thin dielectric layer. Due to the strongly confined plasmonic fields in the thin dielectric layer, the NDs show a large enhancement in the fluorescence intensity without significant degradation in single photon purity. According to the deduced fluorescence lifetime from g((2)) measurements, the Purcell factor is estimated to be similar to 1.4. The plasmonic platform is very ideal for large-area fluorescence enhancement without the needs of sophisticated nanopositioning schemes for locating NDs at local hot spots in conventional plasmonic nanostructures.
Epitaxial Growth of Optically Thick, Single Crystalline Silver Films for Plasmonics
(2019-01-23)
Cheng, Fei
;
Lee, Chien-Ju
;
Choi, Junho
;
Wang, Chun-Yuan
;
Zhan, Qiang
Single crystalline Ag films on dielectric substrates have received tremendous attention recently due to their technological potentials as low loss plasmonic materials. Two different growth approaches have been used to produce single crystalline Ag films previously. One approach is based on repetitive cycles of a two-step process (low temperature deposition followed by RT annealing) using molecular beam epitaxy (MBE), which is extremely time-consuming due to the need for repeat growth cycles. Another approach is based on rapid e-beam deposition which is capable of growing thick single crystalline Ag films (>300 nm) but lacks the precision in thickness control of thin epitaxial films. Here, we report a universal approach to grow atomically smooth epitaxial Ag films by eliminating the repetitive cycles used in the previous two-step MBE method while maintaining the precise thickness control from a few monolayers to the optically thick regime, thus overcoming the limitations of the two aforementioned methods. In addition, we develop an in situ growth of aluminum oxide as the capping layer to protect the epitaxial Ag films. The quality of the epitaxial Ag films was evaluated using a variety of techniques, and the superior optical performance of the films is demonstrated by measuring the propagation length of surface plasmon polaritons (similar to 80 mu m at 632 nm) as well as their capability to support a plasmonic nanolaser in infrared incorporating an InGaAsP quantum well as the gain media.
Giant colloidal silver crystals for low-loss linear and nonlinear plasmonics
(2015-07-01)
Wang, Chun-Yuan
;
Chen, Hung-Ying
;
Sun, Liuyang
;
Chen, Wei-Liang
;
Chang, Yu-Ming
The development of ultrasmooth, macroscopic-sized silver (Ag) crystals exhibiting reduced losses is critical to fully characterize the ultimate performance of Ag as a plasmonic material, and to enable cascaded and integrated plasmonic devices. Here we demonstrate the growth of single-crystal Ag plates with millimetre lateral sizes for linear and nonlinear plasmonic applications. Using these Ag crystals, surface plasmon polariton propagation lengths beyond 100 mm in the red wavelength region are measured. These lengths exceed the predicted values using the widely cited Johnson and Christy data. Furthermore, they allow the fabrication of highly reproducible plasmonic nanostructures by focused ion beam milling. We have designed and fabricated double-resonant nanogroove arrays using these crystals for spatially uniform and spectrally tunable second-harmonic generation. In conventional 'hot-spot'-based nonlinear processes such as surface-enhanced Raman scattering and second-harmonic generation, strong enhancement can only occur in random, localized regions. In contrast, our approach enables uniform nonlinear signal generation over a large area.
Low-Threshold Plasmonic Lasers on a Single-Crystalline Epitaxial Silver Platform at Telecom Wavelength
(2017-06-01)
Lee, Chien-Ju
;
Yeh, Han
;
Cheng, Fei
;
Su, Ping-Hsiang
;
Her, Tsing-Hua
We report on the first demonstration of metal insulator semiconductor-type plasmonic lasers at the telecom wavelength (similar to 1.3 mu m) using top-down fabricated semiconductor waveguides on single-crystalline metallic platforms formed using epitaxially grown Ag films. The critical role of the Ag film thickness in sustaining. plasmonic lasing at the telecom wavelength is investigated systematically. Low-threshold (0.2 MW/cm(2)) and continuous-wave operation of plasmonic lasing at cryogenic temperatures can be achieved on a 150 nm Ag platform with minimum radiation leakage into the substrate. Plasmonic lasing occurs preferentially through higher-order surface-plasmon-polariton modes, which exhibit a higher mode confinement factor, lower propagation loss, and better field gain coupling. We observed plasmonic lasing up to 200 K under pulsed excitations. The plasmonic lasers on large-area epitaxial Ag films open up a scalable platform for on-chip integrations of plasmonics and optoelectronics at the telecom wavelength.
Monolayer Semiconductor Surface-Emitting Lasers Using 2D Dark Plasmonic Cavities
(2018-01-01)
Wang, Chun-Yuan
;
Shi, Jinwei
;
Raja, Soniya S.
;
Chen, Chun-An
;
Zhang, Xin-Quan
We demonstrated a low-threshold lasing from a monolayer gain medium which is made possible due to 2D feedback mechanism via strong exciton-SPP coupling in both real space and a wide range of momentum space.
Nanolasers Employing Epitaxial Plasmonic Layers
(2013-01-01)
Lu, Yu-Jung
;
Kim, Jisun
;
Chen, Hung-Ying
;
Wu, Chihhui
;
Sanders, Charlotte E.
Plasmonic Green Nanolaser Based on a Metal-Oxide-Semiconductor Structure
(2011-10-01)
Wu, Chen-Ying
;
Kuo, Cheng-Tai
;
Wang, Chun-Yuan
;
He, Chieh-Lun
;
Lin, Meng-Hsien
Realization of smaller and faster coherent light sources is critically important for the emerging applications in nanophotonics and information technology. Semiconductor lasers are arguably the most suitable candidate for such purposes. However, the minimum size of conventional semiconductor lasers utilizing dielectric optical cavities for sustaining laser oscillation is ultimately governed by the diffraction limit (similar to(lambda/2n)(3) for three-dimensional (3D) cavities, where lambda is the free-space wavelength and n is the refractive index). Here, we demonstrate the 3D subdiffraction-limited laser operation in the green spectral region based on a metal oxide semiconductor (MOS) structure, comprising a bundle of green-emitting InGaN/GaN nanorods strongly coupled to a gold plate through a SiO(2) dielectric nanogap layer. In this plasmonic nanocavity structure, the analogue of MOS-type "nanocapacitor" in nanoelectronics leads to the confinement of the plasmonic field into a 3D mode volume of 8.0 x 10(-4) mu m(3) (similar to 0.14(lambda/2n)(3)).
Plasmonic Metasurfaces for Nonlinear Optics and Quantitative SERS
(2016-08)
Gwo, Shangjr
;
Wang, Chun-Yuan
;
Chen, Hung-Ying
;
Lin, Meng-Hsien
;
Sun, Liuyang
Plasmonic metasurfaces consist of two-dimensional arrays of metallic nanoresonators (plasmonic "meta-atoms"), which exhibit collective and tunable resonance properties controlled by electromagnetic near-field coupling. These man-made surfaces can produce a range of unique optical properties unattainable with natural materials. In this review, we focus on the emerging applications of metasurfaces with precisely engineered plasmonic properties for nonlinear optics and surface-enhanced Raman spectroscopy (SERS). In practice, these applications are quite susceptible to material losses and structural imperfections, such as variations in size, shape, periodicity of meta-atoms, and their material states (crystallinity, impurity, and oxidation, etc.). In these aspects, conventional top-down lithographic techniques are facing major challenges due to inherent limitations in intrinsic material properties and material quality introduced during growth, synthesis, and fabrication processes, as well as achievable lithographic resolution. Moreover, they are prohibitively expensive and time-consuming for fabrication over large areas. Here, we show that colloidal silver crystals (millimeter-sized single-crystalline plates and thiolate-capped nanoparticles) synthesized by solution-based chemical methods are excellent material platforms for the fabrication of high-quality plasmonic metasurfaces. In, particular, both top-down (focused ion-beam milling) and bottom-up (centimeter-scale self-assembly) techniques can be exploited to generate uniform and precisely engineered colloidal metasurfaces for broadband tunable (across the full visible range) second-harmonic generation and quantitative SERS at the single-molecule level.
Plasmonic Nanolaser Using Epitaxially Grown Silver Film
(1970-01-01)
Lu, Yu-Jung
;
Kim, Jisun
;
Chen, Hung-Ying
;
Wu, Chihhui
;
Dabidian, Nima
"A nanolaser is a key component for on-chip optical communications and computing systems. Here, we report on the low-threshold, continuous-wave operation of a subdiffraction nanolaser based on surface plasmon amplification by stimulated emission of radiation. The plasmonic nanocavity is formed between an atomically smooth epitaxial silver film and a single optically pumped nanorod consisting of an epitaxial gallium nitride shell and an indium gallium nitride core acting as gain medium. The atomic smoothness of the metallic film is crucial for reducing the modal volume and plasmonic losses. Bimodal lasing with similar pumping thresholds was experimentally observed, and polarization properties of the two modes were used to unambiguously identify them with theoretically predicted modes. The all-epitaxial approach opens a scalable platform for low-loss, active nanoplasmonics."
Plasmonic Nanolaser Using Epitaxially Grown Silver Film
(2012-01-01)
Lu, Yu-Jung
;
Kim, Jisun
;
Chen, Hung-Ying
;
Wu, Chihhui
;
Dabidian, Nima
Successful development of epitaxial Ag as a new plasmonic platform has enabled low-threshold, continuous-wave (CW) operation of a SPASER-enabled nanolaser comprised of a subdiffraction plasmonic cavity and a single InGaN@GaN core-shell nanorod gain medium.
Plasmonic whispering-gallery modes in a semiconductor-insulator-metal hybrid structure
(2015)
Lee, Chien-Ju
;
Yeh, Han
;
Chen, Yen-Chun
;
Wang, Chun-Yuan
;
Gwo, Shangir
We demonstrate a plasmonic cavity based on a hybrid semiconductor-insulator-metal structure, which can support plasmonic whispering-gallery modes (WGMs) in the insulator layer. The hybrid structure consists of a semiconductor microdisk with embedded gain medium on top of a single-crystalline gold flake with a nanometer-thick dielectric gap in between. By optimizing the dielectric gap thickness, it is possible to form coupled modes consisting of both photonic WGM in the microdisk and plasmonic WGM in the dielectric gap, by which a high field-gain overlap and an efficient cavity feedback can be achieved for investigating strong light-matter interactions and laser applications.