Switchable Single-Mode Perovskite Microlasers Modulated by

Jan 11, 2018 - However, it still remains a great challenge to simultaneously control the wavelength and mode purity of microscale lasers due to the in...
0 downloads 0 Views 865KB Size
Subscriber access provided by READING UNIV

Communication

Switchable Single-Mode Perovskite Microlasers Modulated by Responsive Organic Microdisks Jinyang Zhao, Yongli Yan, Cong Wei, Wei Zhang, Zhenhua Gao, and Yong Sheng Zhao Nano Lett., Just Accepted Manuscript • DOI: 10.1021/acs.nanolett.7b04834 • Publication Date (Web): 11 Jan 2018 Downloaded from http://pubs.acs.org on January 11, 2018

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

Nano Letters is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 17 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Nano Letters

Switchable Single-Mode Perovskite Microlasers Modulated by Responsive Organic Microdisks Jinyang Zhao, Yongli Yan,* Cong Wei, Wei Zhang, Zhenhua Gao, and Yong Sheng Zhao* Key Laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Science, Beijing 100190, China University of Chinese Academy of Sciences, Beijing 100049, China

ABSTRACT: Miniaturized lasers with high spectra purity and switchable output are of crucial importance for various ultracompact photonic devices. However, it still remains a great challenge to simultaneously control the wavelength and mode purity of microscale lasers due to the insensitive response of traditional materials to external stimuli. In this work, we propose a strategy to realize switchable single-mode microlasers in perovskite microwires (MWs) coupled with responsive organic microdisk cavities. The perovskite MW therein serves as an excellent laser source to deliver multiple lasing modes, while the microdisk functions as a spectral filter to achieve single-mode outcoupling. Furthermore, on account of the sensitive responsiveness of organic materials, reversible wavelength-switching of single-mode laser can be realized through adjusting the resonant modes of the microdisk cavity filter. The results will provide guidance for the rational design of nanophotonic devices with novel performances based on the characteristic of organic materials.

ACS Paragon Plus Environment

1

Nano Letters 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 17

KEYWORDS: single-mode laser, laser switch, responsive organic materials, perovskite laser, organic nanophotonics

Single-mode microlasers hold great potential in applications ranging from sensing, laser display to on-chip optical communication due to the advantages of low noise, good monochromaticity and high output power.1-5 To date, most of single-mode lasers were realized through expanding free spectral range by shortening cavity size until only one mode exists in the resonant cavity.6,7 However, this approach impedes the realization of the wavelength switching that is the key driver for practical applications in wavelength-division multiplexing, wavelength conversion and so on.8-10 Coupled cavity structures, where one cavity acts as a spectral filter to the resonant modes of the other one, not only enable the single-mode operation,11-15 but also offer an opportunity to tailor the lasing wavelength through selectively filtering the resonant modes. In principle, altering the refractive index or size of the microcavity via external stimuli (e.g., temperature, electricity, magnetic field, solvent, etc.) is an effective approach to adjust the resonance modes for tunable lasing.16-19 Nevertheless, the inherent complexities in the device configuration and large footprints restrict their applications in integrated photonics due to the insensitive response of most materials. Organic materials with excellent responsiveness to external stimuli, have been widely demonstrated to be a good platform for tunable optical performances.20,21 Moreover, organic materials take advantage of outstanding structural flexibility, good processability and wide optical window,22-24 making them ideal for the fabrication of various optical microcavities, such as microdisks, isotropic spheres, and hemispheres.25-27 These organic microcavities with high response sensitivity would help to achieve in-situ modulation of the resonant wavelengths

ACS Paragon Plus Environment

2

Page 3 of 17 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Nano Letters

through external stimuli.28,29 Therefore, integrating a responsive organic microcavity with a multimode laser source to construct a coupled cavity system may enable the reversible switching of single-mode lasing by selectively modulating the resonant modes. In this paper, we demonstrate a wavelength-switchable single-mode lasing in an optimized tangentially coupled cavity system constituted with a perovskite microwire (MW) and a vaporresponsive organic microdisk. The perovskite MW therein serves as both gain medium and Fabry-Pérot (FP) resonant microcavity to steadily deliver multiple lasing modes,30,31 while the coupled organic microdisk functions as a spectral filter to the lasing modes of the perovskite MW. The coupled heterogeneous cavities enabled single-mode perovskite lasing when all but one of lasing modes were suppressed by the introduced losses from the microdisk. Based on the sensitive response of the organic flexible microdisk to ambient gas component, we were able to reversibly switch the wavelength of the single-mode laser through the adjustment of microdisk cavity modes via organic vapor. The results afford an approach for in-situ modulation of laser output in composite system, and enlighten the rational design of miniaturized photonic materials and devices with desired performances. The design principle for switchable single-mode lasing is illustrated in Figure 1A. Generally, a single MW with flat end facets can serve as a FP-type microcavity to support multiple modes throughout its gain spectral band.32-34 The prerequisite for lasing action is a greater optical gain than loss,35-38 which thus inspires us to modulate the lasing modes by manipulating the gain and cavity loss. Coupling a responsive organic microdisk whispering-gallery-mode (WGM) resonator to the MW would introduce extra losses at the resonant modes of the microdisk,39 resulting in the suppression of the corresponding lasing modes. Thus, single-mode laser might be realized from the disk coupled MW, when all but one of lasing modes were suppressed. Furthermore, owing to

ACS Paragon Plus Environment

3

Nano Letters 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 4 of 17

highly stimuli-responsive properties of the organic flexible microdisks, the suppressed modes can be effectively modulated by tuning the microdisk resonance via external stimuli, which results in wavelength-switchable single-mode microlasers.

Figure 1. (A) Design principle of the switchable single-mode lasing from a responsive organic microdisk coupled perovskite MW. (B) Schematic illustration of fabrication processes of a coupled microstructure. (C-E) Corresponding bright-field optical microscopy images of fabrication processes of a coupled microstructure. (F) SEM image of coupled microstructures of different size constructed on a single substrate. (G) SEM image of a typical coupled microstructure. (H) Magnified view of the gap region.

ACS Paragon Plus Environment

4

Page 5 of 17 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Nano Letters

Here, the organic-inorganic halide perovskite compound was used to achieve low-threshold lasing because of its high absorption cross sections, efficient photoluminescence (PL), and ultralow bulk defect density.40,41 CH3NH3PbBr3 MWs, which can serve as gain medium and a FP cavity simultaneously (Figure S1), were utilized to generate multimode lasing. In addition, CH3NH3PbBr3 exhibits very good chemical stability,42 making it effective to achieve stable laser emission. By contrast, Polystyrene (PS), which is environment-responsive and transparent in the visible range, was chosen to create high quality responsive microdisk resonator.25 The coupled microstructures were prepared through integrating separate perovskite MWs and microdisks with a micromanipulator, which is illustrated schematically in Figure 1B. First, PS microdisks were obtained by controllably evaporating the solvent of the emulsion solution containing isotropic spherical micelles on the hydrophobic glass substrate (Figure S2).25 Then CH3NH3PbBr3 MWs were synthesized by dropping and evaporating colloid solutions on the same substrate at room temperature.6 After that, the samples were annealed at 60 ℃ for 20 minutes to remove residual solvents, which would be beneficial for further aging and assembling. Finally, adjacent MWs and microdisks were manipulated close to each other (see Supporting Information for details). As shown in the bright field optical microscopy (OM) image (Figure 1C), MWs and microdisks of various sizes can be controllably obtained, facilitating the construction of desired coupled microstructures. The OM images in Figure 1D and E confirm the construction processes that two separate microstructures came close gradually and finally tangentially coupled. The scanning electron microscopy (SEM) images shown in Figure 1F and G further verify the morphology of as-prepared coupled microstructures. Both the MWs and microdisks have smooth surfaces, indicating that very little surface damage and contamination were introduced in the micromanipulation process. Therefore, the coupled microstructures would well preserve the

ACS Paragon Plus Environment

5

Nano Letters 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 6 of 17

excellent optical properties of the individual perovskite NWs and microdisks. The gap between the MW and the microdisk can be as small as ~60 nm (Figure 1H), which is much smaller than λ/2 and thereby permits an effective optical coupling between the two resonators.1

Figure 2. (A) Spatially resolved PL spectra collected from the output port of a CH3NH3PbBr3 MW without (top) and with (bottom) the microdisk coupling, respectively. Inset: corresponding PL images of samples locally excited at one tip of the CH3NH3PbBr3 MW (Ex, marked with a blue circle). Scale bars are 10 µm. (B) Transition of the lasing spectra of the typical CH3NH3PbBr3 NW from multimode to single-mode when it is coupled with a microdisk. Lasing spectra of an isolated MW with (top) and without (middle) the microdisk coupling, respectively. Bottom: the transmittance spectrum of the microdisk filter. (C) Pump fluence-dependent profiles of PL intensities of a coupled microstructure and a single CH3NH3PbBr3 MW, respectively. (D) PL spectra of the coupled microstructure under different pump fluences.

ACS Paragon Plus Environment

6

Page 7 of 17 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Nano Letters

We compared the spatially resolved PL spectra at the output port of a MW with and without the microdisk filter to characterize the optical coupling. When the left tip of the MW (40.9 µm in length) was excited locally with a CW 375 nm ultraviolet laser (labeled as “Ex” in the Figure 2A), PL spectra from the other tip of the MW (labeled as “Out”) were recorded (Figure S3). As shown in Figure 2A, the PL spectrum of the MW coupling with a microdisk exhibits a series of dips from the WGM modulation (the red line), forming a sharp contrast to the broad fluorescence peak of the identical isolated MW (the black line). The experimentally measured dip spacing is inversely proportional to the diameter of microdisk, which is in good accordance with the WGM resonance characteristic (Figure S4). These results further indicate that the dips were originated from the WGM modulation of the microdisk. The normalized transmittance spectrum in decibels (dB, Figure S5) exhibits a considerably large extinction ratio (3-6 dB)39 at the dip positions across the whole spectral range (540-570 nm), implying a strong optical coupling between the MW and the microdisk. The strong optical coupling between the two microcavities provides the feasibility of filtering the lasing modes in MW,43 which can be utilized to achieve single-mode lasers.1,5 Optically pumped lasing measurements were performed on a homebuilt far-field micro-PL system (Figure S3). A pulsed laser beam (800 nm, 150 fs, 1 kHz) was focused on one tip of the MWs and the PL emission from the other tip was recorded, unless stated otherwise. As shown in Figure 2B, the lasing spectrum of an isolated MW (19.2 µm in length) exhibited three sharp peaks, which is a characteristic of multimode operation (Figure S6). In contrast, when this MW was coupled with an organic microdisk (21.3 µm in diameter), single-mode lasing was generated from the coupled microstructure (Figure 2B, top and Figure S7). The positions of the disappeared modes were found to exactly coincide with two dips in the transmittance spectrum of the microdisk (Figure

ACS Paragon Plus Environment

7

Nano Letters 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 8 of 17

2B, middle and bottom). This indicates that the corresponding modes are suppressed by the introduced loss from the microdisk filter. Such a clear mode reduction can also be found in another coupled microstructure, i.e., the number of lasing mode reduced to two (Figure S8) when only one dip position in the transmittance spectrum was consistent with one lasing mode in the MW. It is noteworthy that besides the reduced lasing mode number, the coupling between two cavities did not cause an obvious increase of the lasing threshold (106.6 µJ/cm2 in coupled system vs 100.2 µJ/cm2 in isolated perovskite MW, excited with a 800nm pulsed laser, Figure 2C). In addition, the single-mode operation arisen from microdisk coupling is relatively stable over a large range of pump intensities, as testified by the pump fluence-dependent PL spectra (Figure 2D). These results demonstrate that adopting filtering effect as mode selection mechanism is an effective strategy to realize single-mode lasing. Furthermore, since the output is directly relied on the resonant modes of the microdisk, we might be able to switch the singlemode lasing wavelength by altering the resonance in the disk. The inherent sensitive responsiveness of organic microdisks enables us to experimentally tune the resonant wavelengths of the microdisks via external stimuli. Even a slight change in the surrounding environment would induce a distinct variation of the resonant modes. Here, acetone that can be strongly attached to the surface of PS microdisk due to the interactions between PS and acetone molecules, was harnessed to increase the effective radius of the microdisk cavity.28 According to the WGM theory, there is a one-to-one match between resonant modes and cavity dimension. Therefore, clarifying the relationship between the resonant wavelength shift and acetone vapor concentration is essential to the modulation of the lasing modes from coupled microstructures.

ACS Paragon Plus Environment

8

Page 9 of 17 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Nano Letters

Figure 3. (A) Schematic illustration of the gas response measurement in a sealed glass chamber. (B) Transmittance spectra of a microdisk under exposure of various acetone vapor concentrations. (C) Relationship between resonant wavelength-shift of microdisks and gas concentrations. Blue boxed region indicates the near-linear response range. (D) The evolution of transmittance spectra of a microdisk under the alternate exposure of air and acetone vapor. The characteristics of the actone vapor-controlled microdisk resonance were investigated with a gas flowing system. As schematically illustrated in Figure 3A, the coupled microstructures were put in a sealed glass chamber to provide an atmosphere with constant acetone vapor concentration. The acetone molecules can be strongly adsorbed on the surfaces of the microdisks. With the increase of the acetone concentration, the resonant wavelengths of the microdisk exhibited a gradual red-shift ∆λs (∆λs = λ-λ0, where λ0 and λ are the resonant wavelength before and after gas exposure, respectively, Figure 3B). Figure 3C gives the resonant wavelength shifts

ACS Paragon Plus Environment

9

Nano Letters 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 10 of 17

of a microdisk as a function of gas concentration. ∆λs increased with the increase of acetone concentration. At low acetone concentrations (≤70 ppm), the microdisks exhibited a near-linear response and the response range might be further enlarged using a smaller microcavity due to a smaller mode volume and a larger evanescent field in the surrounding medium (Figure S9). Therefore, by precisely adjusting the concentration of acetone, we can control the wavelength shift to guarantee the exact match of resonance modes between the microdisk and MW, which would help to achieve the expected lasing modes. As the surrounding acetone vapor was removed, the resonant modes of the microdisk would recover to the initial wavelength (Figure 3D), indicating a good reversibilty and reliability of the microdisk filter. The excellent gas responsiveness of organic microdisk provides a feasible method to modulate the wavelength of single-mode lasing by adjusting the acetone concentration. As shown in the simulated electric field distributions of two distinct modes (λ1 and λ2) in a coupled system without acetone vapor (Figure 4A), the optical field of λ1 is well confined in the WGM cavity, while the optical fields of λ2 mainly locates inside the FP cavity, leading to lasing at λ2. The effective radius of the WGM cavity was increased due to the adsorption of acetone molecules, which altered the WGM resonant wavelength from λ1 to λ2, resulting in a switched laser output at λ1 (Figure 4B). The theoretical study fully demonstrates the possibility to achieve switchable single-mode lasing in the responsive organic microdisk coupled MWs through tuning the microdisk resonance. Exactly, this is what we have observed from the experiments. Figure 4C displays the lasing wavelength switching process based on vapor-controlled filtering effect in the coupled microstructure. When the MW (14.7 µm in length) was excited with a pump fluence of 140 µJ/cm2, the coupled microstructure generated a single-mode lasing at 553.2 nm (Figure 4C the

ACS Paragon Plus Environment

10

Page 11 of 17 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Nano Letters

top blue line). Upon exposure to 50 ppm acetone vapor, the organic microdisk (D = 10.3 µm) exhibited a shift of 2.5 nm in resonant wavelengths, which results in the change of the common resonant wavelength (from 550.7 nm to 553.2 nm, the blue dips to red dips shown in Figure 4C). According to the filtering effect, the mode at 553.2 nm would be suppressed and the outputted lasing wavelength was switched to 550.7 nm (Figure S10). Taking into account the good optical stability of CH3NH3PbBr3 MWs under acetone vapor (Figure S11), we are reasonable to ascribe these changes to the response of the microdisk to the ambient gas.

Figure 4. (A,B) Numerically simulated electric field distributions of two modes (λ1 and λ2) in the coupled microstructure under different gas vapor concentrations. (C) Wavelength switching behavior of the lasing spectra (top) and transmittance spectra (bottom) of the coupled

ACS Paragon Plus Environment

11

Nano Letters 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 12 of 17

microstructure before and after acetone exposure. (D) Cyclic switch of the lasing wavelengths and corresponding intensities controlled by the adsorption and desorption of acetone vapor. The reversibility and stability of the gas-responsive lasing output were examined to evaluate the reliability of the coupled structures. In each measurement, the pump fluence was kept at 140 µJ/cm2 to obtain a single-mode lasing at 553.2 nm in air. Then 50 ppm acetone was injected to obtain a lasing wavelength switching to 550.7 nm. After several switching cycles (Figure 4D), the lasing wavelengths and intensities remained nearly unchanged, indicating the good reproducibility and tolerance to the acetone. The excellent performances reveal that the gasresponsive microdisk filters can switch the lasing mode in coupled MWs with high stability. We believe the strategy may offer a new avenue to the realization of tunable single-mode microlasers. In summary, we reported wavelength switchable single-mode microlasers in perovskite MWs that are tangentially coupled with vapor-responsive organic microdisk resonators. The perovskite MW functions as the stable laser source, while the microdisk serves as the mode filter to achieve single-mode operation. With the outstanding responsiveness of organic microdisk to chemical stimuli, the coupled microstructures were proven to be an effective way to controllable mode selection towards switchable single-mode laser. We believe these results would not only present a comprehensive understanding of the relationship among the photonic functions, microstructures and material properties, but also provide a good inspiration for the rational design of controllable coherent light sources, which are indispensable for the photonic integrated circuits.

ASSOCIATED CONTENT

ACS Paragon Plus Environment

12

Page 13 of 17 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Nano Letters

Supporting Information. Materials, characterization and calculation methods. Structure and morphology (Bright-field optical microscopy and SEM image). Experimental setup for the optical characterization. Fluorescence property (transmittance spectrum). Lasing characteristics (microcavity effect, optical stability). This material is available free of charge via the Internet at http://pubs.acs.org. AUTHOR INFORMATION Corresponding Author *Email: [email protected]; [email protected] Notes The authors declare no competing financial interest. ACKNOWLEDGMENT This work was supported financially by the Ministry of Science and Technology of China (2017YFA0204502), the National Natural Science Foundation of China (Grant Nos. 21533013 and 21373241), and the Youth Innovation Promotion Association CAS (2014028). REFERENCES 1.

Gao, H.; Fu, A.; Andrews, S. C.; Yang, P. Proc. Natl. Acad. Sci. U.S.A. 2013, 110, 865-

869. 2.

Duan, X.; Huang, Y.; Agarwal, R.; Lieber, C. M. Nature 2003, 421, 241-245.

3.

Zhang, Q.; Li, G.; Liu, X.; Qian, F.; Li, Y.; Sum, T. C.; Lieber, C. M.; Xiong, Q. Nat.

Commun. 2014, 5, 4953.

ACS Paragon Plus Environment

13

Nano Letters 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

4.

Page 14 of 17

Fan, F.; Turkdogan, S.; Liu, Z.; Shelhammer, D.; Ning, C.-Z. Nat. Nanotechnol. 2015,

10, 796-803. 5.

Zhang, C.; Zou, C.-L.; Dong, H.; Yan, Y.; Yao, J.; Zhao, Y. S. Sci. Adv. 2017, 3,

e1700225. 6.

Zhang, W.; Peng, L.; Liu, J.; Tang, A.; Hu, J. S.; Yao, J.; Zhao, Y. S. Adv. Mater. 2016,

28, 4040-4046. 7.

Yang, Z.; Wang, D.; Meng, C.; Wu, Z.; Wang, Y.; Ma, Y.; Dai, L.; Liu, X.; Hasan, T.;

Liu, X; Yang, Q. Nano Lett. 2014, 14, 3153-3159. 8.

Piccione, B.; Cho, C.-H.; van Vugt, L. K.; Agarwal, R. Nat. Nanotechnol. 2012, 7, 640-

645. 9.

Dong, H.; Zhang, C.; Lin, X.; Zhou, Z.; Yao, J.; Zhao, Y. S. Nano Lett. 2017, 17, 91-96.

10.

Yang, A.; Hoang, T. B.; Dridi, M.; Deeb, C.; Mikkelsen, M. H.; Schatz, G. C.; Odom, T.

W. Nat. Commun. 2015, 6, 6939. 11.

Eaton, S. W.; Fu, A.; Wong, A. B.; Ning, C.-Z.; Yang, P. Nat. Rev. Mater. 2016, 1,

16028. 12.

Xiao, Y.; Meng, C.; Wang, P.; Ye, Y.; Yu, H.; Wang, S.; Gu, F.; Dai, L.; Tong, L. Nano

Lett. 2011, 11, 1122-1126. 13.

Xu, H.; Wright, J. B.; Luk, T.-S.; Figiel, J. J.; Cross, K.; Lester, L. F.; Balakrishnan, G.;

Wang, G. T.; Brener, I.; Li, Q. Appl. Phys. Lett. 2012, 101, 113106. 14.

Ta, V. D.; Chen, R.; Sun, H. D. Adv. Opt. Mater. 2014, 2, 220-225.

15.

Xiao, Y.; Meng, C.; Wu, X.; Tong, L. Appl. Phys. Lett. 2011, 99, 023109.

16.

Shoji, Y.; Kintaka, K.; Suda, S.; Kawashima, H.; Hasama, T.; Ishikawa, H. Opt. Express

2010, 18, 9071-9075.

ACS Paragon Plus Environment

14

Page 15 of 17 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Nano Letters

17.

Guarino, A.; Poberaj, G.; Rezzonico, D.; Degl'Innocenti, R.; Günter, P. Nat. Photonics

2007, 1, 407-410. 18.

Bi, L.; Hu, J.; Jiang, P.; Kim, D. H.; Dionne, G. F.; Kimerling, L. C.; Ross, C. A. Nat.

Photonics 2011, 5, 758-762. 19.

Li, H.; Shang, L.; Tu, X.; Liu, L.; Xu, L. J. Am. Chem. Soc. 2009, 131, 16612-16613.

20.

Yerushalmi, R.; Scherz, A.; van der Boom, M. E.; Kraatz, H.-B. J. Mater. Chem. 2005,

15, 4480. 21.

Sagara, Y.; Kato, T. Nat. Chem. 2009, 1, 605-610.

22.

Chandrasekhar, N.; Chandrasekar, R. Angew. Chem. Int. Ed. 2012, 51, 3556-3561.

23.

Yin, D.; Feng, J.; Ma, R.; Liu, Y.-F.; Zhang, Y.-L.; Zhang, X.-L.; Bi, Y.-G.; Chen, Q.-D.;

Sun, H.-B. Nat. Commun. 2016, 7, 11573. 24.

Zhang, C.; Zou, C.-L.; Zhao, Y.; Dong, C.-H.; Wei, C.; Wang, H.; Liu, Y.; Guo, G.-C.;

Yao, J.; Zhao, Y. S. Sci. Adv. 2015, 1, e1500257. 25.

Wei, C.; Liu, S.-Y.; Zou, C.-L.; Liu, Y.; Yao, J.; Zhao, Y. S. J. Am. Chem. Soc. 2014,

137, 62-65. 26.

Adachi, T.; Tong, L.; Kuwabara, J.; Kanbara, T.; Saeki, A.; Seki, S.; Yamamoto, Y. J.

Am. Chem. Soc. 2013, 135, 870-876. 27.

Ta, V. D.; Chen, R.; Sun, H. D. Adv. Mater. 2012, 24. OP60-OP64.

28.

Gao, M.; Wei, C.; Lin, X.; Liu, Y.; Hu, F.; Zhao, Y. S. Chem. Commun. 2017, 53, 3102-

3105. 29.

Ward, J.; Benson, O. Laser Photonics Rev. 2011, 5, 553-570.

30.

Zhu, H.; Fu, Y.; Meng, F.; Wu, X.; Gong, Z.; Ding, Q.; Gustafsson, M. V.; Trinh, M. T.;

Jin, S.; Zhu, X. Y. Nat. Mater. 2015, 14, 636-642.

ACS Paragon Plus Environment

15

Nano Letters 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

31.

Page 16 of 17

Xing, J.; Liu, X. F.; Zhang, Q.; Ha, S. T.; Yuan, Y. W.; Shen, C.; Sum, T. C.; Xiong, Q.

Nano Lett. 2015, 15, 4571-4577. 32.

Zhang, C.; Zou, C.-L.; Yan, Y.; Hao, R.; Sun, F.-W.; Han, Z.-F.; Zhao, Y. S.; Yao, J. J.

Am. Chem. Soc. 2011, 133, 7276-7279. 33.

Yan, R.; Gargas, D.; Yang, P. Nat. Photonics 2009, 3, 569-576.

34.

Zhou, H.; Yuan, S.; Wang, X.; Xu, T.; Wang, X.; Li, H.; Zheng, W.; Fan, P.; Li, Y.; Sun,

L.; Pan, A. ACS Nano 2017, 11, 1189-1195. 35.

Clark, J.; Lanzani, G. Nat. Photonics 2010, 4, 438-446.

36.

Guo, P.; Zhuang, X.; Xu, J.; Zhang, Q.; Hu, W.; Zhu, X.; Wang, X.; Wan, Q.; He, P.;

Zhou, H.; Pan, A. Nano Lett. 2013, 13, 1251-1256. 37.

Pan, A.; Liu, D.; Liu, R.; Wang, F.; Zhu, X.; Zou, B. Small 2005, 1, 980-983.

38.

Wang, X.; Zhuang, X.; Yang, S.; Chen, Y.; Zhang, Q.; Zhu, X.; Zhou, H.; Guo, P.; Liang,

J.; Huang, Y.; Pan, A.; Duan, X. Phys. Rev. Lett. 2015, 115, 027403. 39.

Takazawa, K.; Inoue, J.-i.; Mitsuishi, K.; Takamasu, T. Adv. Mater. 2011, 23, 3659-3663.

40.

Xing, G.; Mathews, N.; Lim, S. S.; Yantara, N.; Liu, X.; Sabba, D.; Gratzel, M.;

Mhaisalkar, S.; Sum, T. C. Nat. Mater. 2014, 13, 476-480. 41.

Zhang, N.; Sun, W.; Rodrigues, S. P.; Wang, K.; Gu, Z.; Wang, S.; Cai, W.; Xiao, S.;

Song, Q. Adv. Mater. 2017, 29, 1606205. 42.

Li, Y. J.; Lv, Y.; Zou, C.-L.; Zhang, W.; Yao, J.; Zhao, Y. S. J. Am. Chem. Soc. 2016,

138, 2122-2125. 43.

Xu, J.; Zhuang, X.; Guo, P.; Zhang, Q.; Huang, W.; Wan, Q.; Hu, W.; Wang, X.; Zhu,

X.; Fan, C.; Yang, Z.; Tong, L.; Duan, X.; Pan, A. Nano Lett. 2012, 12, 5003-5007.

ACS Paragon Plus Environment

16

Page 17 of 17 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Nano Letters

ACS Paragon Plus Environment

17