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Abstract
Förster resonance energy transfer (FRET) is a well-known physical phenomenon, which has been widely used in a variety of fields, spanning from chemistry, and physics to optoelectronic devices. In this study, giant enhanced FRET for donor-acceptor CdSe/ZnS quantum dot (QD) pairs placed on top of Au/MoO3 multilayer hyperbolic metamaterials (HMMs) has been realized. An enhanced FRET transfer efficiency as high as 93% was achieved for the energy transfer from a blue-emitting QD to a red-emitting QD, greater than that of other QD-based FRET in previous studies. Experimental results show that the random laser action of the QD pairs is greatly increased on a hyperbolic metamaterial by the enhanced FRET effect. The lasing threshold with assistance of the FRET effect can be reduced by 33% for the mixed blue- and red-emitting as QDs compared to the pure red-emitting QDs. The underlying origins can be well understood based on the combination of several significant factors, including spectral overlap of donor emission and acceptor absorption, the formation of coherent closed loops due to multiple scatterings, an appropriate design of HMMs, and the enhanced FRET assisted by HMMs.
© 2023 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement
1. Introduction
Förster resonance energy transfer (FRET) is a nonradiative mechanism describing the transfer of excited state energy from a donor fluorophore to an acceptor fluorophore through a dipole-dipole coupling process [1,2]. FRET can be used as a spectroscopic ruler to measure distance and detect molecular interactions in several systems, having applications in biophysics, biochemistry [3], organic photovoltaics [4], light-emitting devices [5], etc. Recently, it has been shown that some special structures such as plasmonic nanostructures, nanocavities, nanoparticles, and nanoantennas can produce peculiar electromagnetic environments through the engineering of their local density of optical states (LDOS), which has been utilized for controlling the spontaneous emission and FRET [6–11]. Thus, manipulating LDOS could enhance the FRET rate and improve the performance of FRET-based optoelectronic devices.
During the past decade, the surface plasmon resonance of metal nanoparticles has been widely used to generate strong optical fields due to the enhancement of LDOS, which increases the absorption cross-section and radiative recombination rate of fluorophores [12]. Accordingly, surface plasmon resonance can also increase the rate of energy transfer between donors and acceptors by adjusting LDOS and enhancing FRET efficiency [13,14]. However, enhancement of the LDOS with metal nanoparticles is limited by the relatively narrow band of surface plasmon resonance, which restricts the FRET enhancement to the proximity of the wavelength in plasmon resonance. Hyperbolic metamaterials (HMMs) are anisotropic materials that behave like metals for light propagating in one direction, but behave like dielectrics for light propagating along a different axis of the crystal [15,16]. HMMs enable to produce intense light-matter interactions because of a large LDOS and highly localized electric fields, leading to efficient emission enhancement and control of light directivity. HMMs are expected to influence the rate of spontaneous emission and the FRET process. In particular, the hyperbolic dispersion is very broad, extending from visible to near-infrared spectral region, which is advantageous for applications in optoelectronic devices [15,17–23] Because of the singularity in LDOS, HMMs demonstrate significant Purcell effects and enable to increase the stimulated emission of a gain medium. Thus, HMMs can be utilized to facilitate lasing action for emitters as long as the stimulated emission rate is sufficiently large and the light is adequately amplified. For example, a random laser with core-shell HMM structures for ultralow lasing threshold has been recently demonstrated [24]. In this paper, we experimentally investigate the FRET process between the donor and acceptor CdSe/ZnS quantum dots (QDs) on top of the HMMs, consisting of alternating layers of Ag and MoO3. It is found that with a suitable design of HMM structures, the emission intensity of acceptor QDs can be greatly enhanced and the FRET efficiency can be significantly increased. Moreover, a significant reduction of the lasing threshold for the acceptor QD lasing, originated from a strong FRET effect, has been demonstrated as the QDs are placed in the proximity of a HMM. Our study demonstrates that the enhanced FRET efficiency by HMMs may provide an excellent platform for the development of high-performance optoelectronic devices.
2. Experimental setup and device design
All the photoluminescence (PL) spectra and random laser action were measured by a pulsed diode laser (PicoQuant, PDL 800-B) with a wavelength of 374 nm, a repetition rate of 2.5 MHz, and a pulse duration of 70 ps. The signal of random laser action was detected by a photomultiplier (PMT) and recorded by Horiba Jobin Yvon TRIAX 320 spectrometer equipped with a 100x objective lens (Olympus, Japan). The integration time and the resolution of the spectrometer are 0.5 s, and 0.1 nm, respectively. We used time-correlated single photon counting (TCSPC) to analyze the dynamics of the charge carrier mechanism so that we could measure the lifetime of the device. TCSPC is a common method to measure the time difference between the excitation signal from the device and the emitted photons arriving at the detector. A fitting software (FluoFit, PicoQuant) was used to estimate the lifetime of the device measured by TCSPC. Figure 1 shows the experimental setup for PL measurements, which includes a photograph (inset).
Fig. 1. Schematiac of the experimental setup for PL measurements. Inset shows a photograph of the setup.
The structure of HMM in this work is composed of Au/MoO3 with a thickness of 30/10 nm for four pairs. Based on the FDTD simulation, the Purcell maximum is located at the overlap in the emission spectrum of the blue-emitting QD donors and the absorption spectrum of the red-emitting QD acceptors, which will be shown below. The fabrication processes of the HMMs are shown in Fig. 2. First, a 10 nm thick MoO3 film was deposited on a silicon substrate by a thermal evaporation system under the chamber pressure of 10−6 Torr and the deposition rate was 0.4 Å/s. Next, a 30 nm thick gold film was deposited by a thermal evaporation system under the chamber pressure of 10−6 Torr and the deposition rate was 0.3 Å/s. After repeating the above-mentioned processes 4 times, an 8 nm thick MoO3 film was deposited by a thermal evaporation system. On the other hand, we spin-coated the CdSe/ZnS QDs with the emission wavelength centered at 460 nm, 531 nm, and 627 nm and assigned them as the blue-, green-, and red-emitting QDs, respectively. Also, the mixture of blue- (green-) and red-emitting QDs with the optimized mixed ratio of 1/1 has been deposited on the glass substrate and the HMM structure with an angular velocity of 1000 rpm for 90 seconds.
The simulation in this work was obtained from the commercial electromagnetic software (Lumerical) for finite- difference time-domain (FDTD) solutions. The refractive indices of Au, MoO3, and CdSe as well as ZnS were taken from the database of Johnson and Christy [25], Lajaunie et al. [26], and Palik et al. [27], respectively. A perfectly matched layer boundary condition was used to cover the boundaries of the computational domain to prevent reflection from the domain boundaries. The mesh resolution was set to 1 nm to obtain high-accuracy results.
3. Results and discussion
In this study, two different substrates (glass and HMMs) were utilized to investigate the influence of Au/MoO3 multilayer HMMs on the FRET process. Two QD donors (the green- and blue-emitting CdSe/ZnS QDs) were used for the FRET study, and red-emitting CdSe/ZnS QDs were employed as acceptors. PL measurements with an excitation wavelength of 374 nm and a pumping energy density of 1.64 kWcm-2 were performed to examine the change of FRET from a donor QD to an acceptor QD. Figure 3(a), shows the PL spectra measured from pure green-emitting QDs (donors), pure red-emitting QDs (acceptors) and the mixture of both QDs on glass substrate. A decrease in PL in green light and a simultaneous increase in red light was observed in the mixed QDs. The PL spectra of the pure blue-emitting QDs, red-emitting QDs and the mixture of both QDs on glass are shown in Fig. 3(b). Similarly, the PL of blue light decreases and that of red light increases for the mixture of QDs. The above observations demonstrate that the FRET occurs from donor QDs to acceptor QDs. To further prove the existence of FRET, time-resolved PL measurements were performed. Figures 3(c), 3(d), and 3(e) show the PL decay profiles of the green-, blue-, and red-emitting QDs in pure and mixed QDs on the glass substrate, respectively. Obviously, compared to pure QDs, the PL lifetimes of the green- (blue-) emitting QDs decrease in the presence of red-emitting QDs. On the other hand, the PL lifetime of red-emitting QDs increases as they are mixed with donor QDs. Because of the existence of the FRET effect, the photogenerated carriers in donors have an additional channel to transfer energy to the acceptor, which will accelerate the relaxation of the excited carriers and shorten the lifetime. In stark contrast, the emission arising from acceptors possesses an additional channel of excess energy transferred from donors, and the lifetime becomes longer. Thus, the above observations are in agreement with the FRET behavior.
Fig. 3. Photoluminescence (PL) characteristics of quantum dots (QDs) on glass at a pumping energy density of 1.64 kWcm-2. PL spectra of (a) green-emitting QDs, red-emitting QDs, and the mixed green- and red-emitting QDs, (b) blue-emitting QDs, red-emitting QDs, and the mixed blue- and red-emitting QDs. PL decay profiles of the pure and mixed QDs monitored at (c) 531 nm, (d) 460 nm, (e) 627 nm.
To obtain the PL lifetime, a stretched-exponential function was used to fit the PL decay traces in Figs. 3(c) and 3(d) [28]:
where n(t), k, and β and are the donor concentration, the PL decay rate in donors and the dispersion factor, respectively. By using Eq. (1) the fitted curves are shown as solid lines in Figs. 2(c) and 2(d), which are in good agreement with the experimental data. The average PL lifetime in such a stretched exponential function can be calculated as follows [29]:Fig. 4. Donor QDs (blue- and green-emitting QDs) emission spectra and acceptor QDs (red-emitting QDs) absorption spectrum. Maximum intensity values were normalized to one.
The effect of HMM on the FRET process has been examined by the PL intensity of the QD-QD pairs on top of HMMs. Figures 5(a) and 5(b) show the PL spectra measured from pure donor QDs, pure acceptor QDs, and the mixture of both QDs on HMMs. Similar to the case in the glass substrate, an obvious decrease of PL from the donor QDs and a simultaneous increase of PL from the acceptor QDs was also observed for the mixed QDs. In Figs. 5(a) and 5(b), the PL from the donor-acceptor QD pairs shows several sharp spikes. This interesting behavior is similar to the random laser action observed in many previous reports [18,24]. Figure 5(c) displays comparison of the PL intensities of pure green- and blue-emitting QDs on glass and HMMs. The PL intensity is enhanced for both QDs as the substrate changes from glass to HMMs. Compared to blue-emitting QDs, the PL of green-emitting QDs on HMMs enhances more significantly. This could be accounted for by the Purcell effect, which will be discussed below.
Fig. 5. Photoluminescence characteristics of QDs on the Au/MoO3 multilayer hyperbolic metamaterials (HMMs) at a pumping energy density of 1.64 kWcm-2. PL spectra of (a) green-emitting QDs, red-emitting QDs, and mixed green- and red-emitting QDs, (b) blue-emitting QDs, red-emitting QDs, and mixed blue- and red-emitting QDs, (c) PL spectra of green- and blue-emitting QDs on different substrates (glass and HMM). PL decay profiles of pure and mixed QDs monitored at (d) 531 nm, (e) 460 nm, (f) 627 nm.
Figures 5(d), 5(e), and 5(f) display the PL decay profiles of the green-, blue-, and red-emitting QDs in pure and mixed QDs on top of HMMs, respectively. On the basis of a stretched-exponential function, the PL decay traces of all QDs were fitted and the average PL lifetimes were calculated using Eq. (2). With the HMMs, the PL lifetimes of the green- (blue-) emitting QDs in the absence and presence of red-emitting QDs were found to be 4.81 (1.60) ns and 1.28 (0.11) ns, respectively. When QDs are placed on the top of HMMs, the FRET efficiency using the green- and blue-emitting QDs as the donors is calculated to be 73% and 93%, respectively. Compared with the glass substrate, the FRET efficiency for the QD-QD pairs is enhanced significantly with the HMMs. To the best of our knowledge, the highest FRET efficiency in this work (93%) is greater than that of other reports from previous QD-based FRET (46%∼80%) [31–33]. This efficiency is also larger than that of the FRET with HMMs in a configuration where the donors are present in the opposite side of the acceptors (32%∼68%) [33,34].
FRET can be enhanced by metals due to the plasmon effect or localized surface plasmon resonance. [35,36]. In the case of plasmon-enhance FRET, the large wavevector states are absorbed totally, producing an increase in the nonradiative decay rate and leading to luminescence quenching [35]. The surface plasmon effect may cause a reduction in the lifetime of the acceptor excited states, which is related to an enhancement in the local density of optical states [36]. The enhanced FRET efficiency due to surface plasmon is about 79%, [35] which is smaller than the efficiency (93%) in our case. High FRET efficiency would be beneficial in FRET detection, producing a potential application in biomolecular sensors. It is well known that surface-plasmon-based sensors are widely used in biosensing. [36–38] However, detection of small biomolecular species at very low concentrations remains difficult. Due to its high sensitivity to distance, a FRET-based sensor may provide an alternative method to study the low-concentration molecular-level interaction. It should be noted that the rate of spontaneous emission is only influenced in the near field of a HMM. Therefore, donors and acceptors should be within the proximity of HMMs to enhance FRET.
To verify whether the Purcell effect is responsible for the enhancement of PL and FRET efficiency, the Purcell factor for our HMMs was calculated using the commercial electromagnetic software numerical Finite-Difference Time-Domain (FDTD). The Purcell factor with a dipole source above the HMMs is obtained from Fiso = 1/3 F⊥+ 2/3 F‖, where F⊥ and F‖ are the dipoles perperdicular and parallel to the substrate, respectively [18]. Figure 6 displays the calculated Purcell factor with a dipole at 10 nm above our Au/MoO3 multilayer HMMs. The calculation shows that the Purcell factor is high in the visible regime with a maximum of 55 at the central emission wavelength of 520 nm. This is in good agreement with the measured results in Fig. 5(c), which shows that the PL of QDs can be greatly enhanced on top of Au/MoO3 HMMs. In particular, the PL of green-emitting QDs was enhanced more significantly than that of blue-emitting QDs because the former emission wavelength is close to the maximum wavelength of the Purcell factor. Thus, the PL enhancement due to Au/MoO3 HMMs is associated with the Purcell effect. On the other hand, it is noteworthy that the FRET enhancement in green-red assembles is smaller than that in blue-red assembles (Figs. 5(a) and 5(b)), different from the case in PL enhancement. We suggest that the overlap of acceptor absorption and donor emission is also essential in the FRET process on Au/MoO3 HMMs. In Fig. 4, the absorption spectrum of the red-emitting QDs has more overlapping area with the emission spectrum of the blue-emitting QDs than that with the green-emitting QDs. With a combined effect of the Purcell factor and the spectral overlapping, the FRET on Au/MoO3 HMMs reveals a larger enhancement in blue-red assembles than that in green-red assembles, as shown in Fig. 5. Thus, in addition to the Purcell factor, the overlap of acceptor absorption and donor emission also play an important role in the FRET of QD assembles on Au/MoO3 HMMs.
To explore the random laser action of the PL spectrum, the QDs were deposited on top of HMMs by varying the pumping energy density. Figures 7(a) and 7(b) show the PL spectra of red-emitting QDs under three different pumping energy densities (0.96, 1.64, and 2.70 kWcm-2) on top of glass and HMMs, respectively. No laser action from red-emitting QDs was observed even under the high pumping energy density. Figures 7(c) and 7(d) show the dependence of the pumping energy density on the PL spectra of the red-mitting QDs mixed with the green-emitting QDs on top of glass and HMMs, respectively. Compared to the PL spectra of pure red-emitting QDs, the PL intensity of the mixed QDs enhances for both substrates. In addition, several sharp spikes appear on top of a broad emission background when the mixed QDs are deposited on HMMs under the pumping energy density of 2.70 kWcm-2 as shown in Fig. 7(d). The enhanced peak intensity and reduced spectral line width are characteristics of random lasing, originating from the multiple light scattering created by the inhomogenous internal structures. The appearance of random lasing in the donor-acceptor QD pairs, but not in the pure acceptor QDs, reveals that the random lasing behavior can be triggered by the enhanced FRET. This can be partly due to the increased scattering efficiency for the QDs located on the top of HMMs, which is advantageous for the creation of the closed loops to accomplish the random laser action [18]. In addition, spontaneous emission for both donors and acceptors can be enhanced by HMMs in the mixed QD system, which is also helpful for the occurrence of random lasing in the FRET process. Thus, according to our results, the enhanced FRET process assisted by HMMs not only enhances the emission intensity of QDs but also provides an excellent platform for the creation of laser action. Figures 6(e) and 6(f) display the dependence of the pumping energy density on the PL spectra of the red-mitting QDs mixed with the blue-emitting QDs on top of glass and HMMs, respectively. Compared with the case in the green- and red-emitting QDs (Fig. 7(d)), the random laser originating from blue- and red-emitting QDs on HMMs exhibits more intense and sharp peaks. This is explained by the more pronounced FRET effect for the blue- and red-emitting QD pairs, which provides enhancement of spontaneous emission in two gain materials and assists random lasing in a multi-energy level system. To further examine the random laser action, the dependence of the integrated peak intensity on the pumping energy density for pure and mixed QDs is plotted in Fig. 8. Laser threshold behavior was occurred for all samples on HMMs, but not for those on the glass substrate. The lasing thresholds were obtained to be 2.60, 2.10, and 1.74 kW cm-2 for the pure red-emitting QDs, the mixed green- and red-emitting QDs, and the mixed blue- and red-emitting QDs, respectively. The lasing threshold with the FRET effect is reduced by 19% and 33% for the former and latter, respectively, as compared to the pure QDs without the enhanced FRET process. The reduced lasing threshold is caused by the introduction of HMMs, which facilitates the propagation of the out-coupling power of the high-k modes to the far field and improves light trapping for the enhanced lasing action [39].
Fig. 7. Dependence of the pumping energy density on PL spectra of red-emitting QDs on (a) glass and (b) HMMs. Dependence of the pumping energy density on PL spectra of mixed green- and red-emitting QDs on (c) glass and (d) HMMs. Dependence of the pumping energy density on PL spectra of the blue- and red-emitting QDs on (e) glass and (f) HMMs.
Fig. 8. Maximum PL intensities plotted as a function of pumping energy density for (a) pure red-emitting QDs (b) mixture of green- and red-emitting QDs (c) mixture of blue- and red-emitting QDs. The fitted lines with relatively flat slopes correspond to the spontaneous emission, and those with sharp slopes correspond to the stimulated emission. The intersections between the flat and sharp slopes are the laser thresholds.
4. Conclusion
We have successfully demonstrated that HMMs can be used to enhance the FRET effect. We investigated the energy transfer between donor QDs and acceptor QDs with different combinations of emission and absorption spectra. It is found that the larger overlap of the donor emission spectrum and the acceptor absorption spectrum results in the higher efficiency of FRET. An enhanced FRET transfer efficiency as high as 93% has been attained for mixed blue- and red-emitting QDs. Compared with previous FRET reports based on QDs, the FRET transfer efficiency located on HMMS has the highest value. Furthermore, the random laser action that is not seen on glass substrates can be clearly observed after the introduction of HMMs, indicating that the FRET effect enhanced by HMMs is valuable for driving lasing action. The random laser action assisted by HMMs is made possible by the integration of several factors, including the overlap of emission spectrum of the donor and absorption spectrum of the acceptor, the formation of coherent closed loops due to multiple scattering, the suitable design of HMM structures, and the enhanced FRET process. Compared with the pure red-emitting QDs, the optimal random lasing and a 33% lower lasing threshold were acquired with mixed QDs on top of HMMs corresponding to energy transfer from blue-emitting QD donors to red-emitting QD acceptors. Because of the importance of the FRET process and laser action in a wide variety of fields, the study shown here should be very useful and timely for the development of not-yet realized high-performance devices with applications covering from optoelectronics to bio-imaging.
Funding
Ministry of Science and Technology, Taiwan (109-2112-M-033-MY3, 110-2112-M-002-044, 111-2112-M-033-008, 111-2634-F-002 -016).
Acknowledgments
This work was financially supported by the “Advanced Research Center for Green Materials Science and Technology” from the Featured Area Research Center Program within the framework of the Higher Education Sprout Project by the Ministry of Education (111L9006) and the Ministry of Science and Technology in Taiwan (MOST111-2634-F-002 -016, MOST 110-2112-M-002-044, MOST 111-2112-M-033-008, MOST 109-2112-M-033-006-MY3).
Disclosures
The authors declare no conflicts of interest.
Data availability
Data are available from the corresponding author upon reasonable request.
References
1. A. R. Clapp, I. L. Medintz, and H. Mattoussi, “Förster resonance energy transfer Investigations using quantum-dot fluorophores,” ChemPhysChem 7, 47–57 (2006). [CrossRef]
2. D. J. Roth, M. E. Nasir, P. Ginzburg, P. Wang, A. le Marois, K. Suhling, D. Richards, and A. V. Zayats, “Förster resonance energy transfer inside hyperbolic metamaterials,” ACS Photonics 5(11), 4594–4603 (2018). [CrossRef]
3. Q. Chen, X. Zhang, Y. Sun, M. Ritt, S. Sivaramakrishnan, and X. Fan, “Highly sensitive fluorescent protein FRET detection using optofluidic lasers,” Lab Chip 13(14), 2679 (2013). [CrossRef]
4. B. E. Hardin, E. T. Hoke, P. B. Armstrong, J. H. Yum, P. Comte, T. Torres, J. M. J. Fréchet, M. K. Nazeeruddin, M. Grätzel, and M. D. McGehee, “Increased light harvesting in dye-sensitized solar cells with energy relay dyes,” Nat. Photonics 3(7), 406–411 (2009). [CrossRef]
5. S. Brovelli, F. Meinardi, G. Winroth, O. Fenwick, G. Sforazzini, M. J. Frampton, L. Zalewski, J. A. Levitt, F. Marinello, P. Schiavuta, K. Suhling, H. L. Anderson, and F. Cacialli, “White electroluminescence by supramolecular control of energy transfer in blends of organic-soluble eEncapsulated polyfluorenes,” Adv. Funct. Mater. 20(2), 272–280 (2010). [CrossRef]
6. T. Nakamura, M. Fujii, K. Imakita, and S. Hayashi, “Modification of energy transfer from Si nanocrystals to Er3 + near a Au thin film,” Phys. Rev. B 72(23), 235412 (2005). [CrossRef]
7. T. Nakamura, M. Fujii, S. Miura, M. Inui, and S. Hayashi, “Enhancement and suppression of energy transfer from Si nanocrystals to Er ions through a control of the photonic mode density,” Phys. Rev. B 74(4), 045302 (2006). [CrossRef]
8. Q. C. Sun, H. Mundoor, J. C. Ribot, V. Singh, I. I. Smalyukh, and P. Nagpal, “Plasmon-enhanced energy transfer for improved upconversion of infrared radiation in doped-lanthanide nanocrystals,” Nano Lett. 14(1), 101–106 (2014). [CrossRef]
9. C. Blum, N. Zijlstra, A. Lagendijk, M. Wubs, A. P. Mosk, and V. Subramaniam, “Nanophotonic control of the Förster resonance energy transfer efficiency,” Phys. Rev. Lett. 109(20), 203601 (2012). [CrossRef]
10. F. T. Rabouw, S. A. den Hartog, T. Senden, and A. Meijerink, “Photonic effects on the Förster resonance energy transfer efficiency,” Nat. Commun. 5(1), 3610 (2014). [CrossRef]
11. M. J. A. de Dood, J. Knoester, A. Tip, and A. Polman, “Förster transfer and the local optical density of states in erbium-doped silica,” Phys. Rev. B 71(11), 115102 (2005). [CrossRef]
12. K. T. Shimizu, W. K. Woo, B. R. Fisher, H. J. Eisler, and M. G. Bawendi, “Surface-enhanced emission from single semiconductor nanocrystals,” Phys. Rev. Lett. 89(11), 117401 (2002). [CrossRef]
13. V. K. Komarala, A. L. Bradley, Y. P. Rakovich, S. J. Byrne, Y. K. Gun’ko, and A. L. Rogach, “Surface plasmon enhanced Förster resonance energy transfer between the CdTe quantum dots,” Appl. Phys. Lett. 93(12), 123102 (2008). [CrossRef]
14. C. H. Wang, C. W. Chen, Y. T. Chen, C. M. Wei, Y. F. Chen, C. W. Lai, M. L. Ho, P. T. Chou, and M. Hofmann, “Surface plasmon enhanced energy transfer between type I CdSe/ZnS and type II CdSe/ZnTe quantum dots,” Appl. Phys. Lett. 96(7), 071906 (2010). [CrossRef]
15. A. Poddubny, I. Iorsh, P. Belov, and Y. Kivshar, “Hyperbolic metamaterials,” Nat. Photonics. 7(12), 948–957 (2013). [CrossRef]
16. L. Ferrari, C. Wu, D. Lepage, X. Zhang, and Z. Liu, “Hyperbolic metamaterials and their applications,” Prog. Quantum Electron. 40, 1–40 (2015). [CrossRef]
17. C. L. Cortes, W. Newman, S. Molesky, and Z. Jacob, “Quantum nanophotonics using hyperbolic metamaterials,” J. Opt. (Bristol, U. K.) 14(6), 063001 (2012). [CrossRef]
18. G. Haider, H. I. Lin, K. Yadav, K. C. Shen, Y. M. Liao, H. W. Hu, P. K. Roy, K. P. Bera, K. H. Lin, H. M. Lee, Y. T. Chen, F. R. Chen, and Y. F. Chen, “A Highly-efficient single segment white random laser,” ACS Nano 12(12), 11847–11859 (2018). [CrossRef]
19. G. Palermo, K. V. Sreekanth, N. Maccaferri, G. E. Lio, G. Nicoletta, F. de Angelis, M. Hinczewski, and G. Strangi, “Hyperbolic dispersion metasurfaces for molecular biosensing,” Nanophotonics 10(1), 295–314 (2020). [CrossRef]
20. H. I. Lin, K. C. Shen, S. Y. Lin, G. Haider, Y. H. Li, S. W. Chang, and Y. F. Chen, “Transient and Flexible Hyperbolic Metamaterials on Freeform Surfaces,” Sci. Rep. 8(1), 9469 (2018). [CrossRef]
21. G. Palermo, G. E. Lio, M. Esposito, L. Ricciardi, M. Manoccio, V. Tasco, A. Passaseo, A. de Luca, and G. Strangi, “Biomolecular sensing at the interface between chiral metasurfaces and hyperbolic metamaterials,” ACS Appl. Mater. Interfaces 12(27), 30181–30188 (2020). [CrossRef]
22. K. C. Shen, C. Hsieh, Y. J. Cheng, and D. P. Tsai, “Giant enhancement of emission efficiency and light directivity by using hyperbolic metacavity on deep-ultraviolet AlGaN emitter,” Nano Energy 45, 353–358 (2018). [CrossRef]
23. K. V. Sreekanth, Y. Alapan, M. Elkabbash, E. Ilker, M. Hinczewski, U. A. Gurkan, A. de Luca, and G. Strangi, “Extreme sensitivity biosensing platform based on hyperbolic metamaterials,” Nat. Mater. 15(6), 621–627 (2016). [CrossRef]
24. H. I. Lin, K. Yadav, K. C. Shen, G. Haider, P. K. Roy, M. Kataria, T. J. Chang, Y. H. Li, T. Y. Lin, Y. T. Chen, and Y. F. Chen, “Nanoscale core–shell hyperbolic structures for ultralow threshold laser action: an efficient platform for the enhancement of optical manipulation,” ACS Appl. Mater. Interfaces 11(1), 1163–1173 (2019). [CrossRef]
25. P. B. Johnson and R. W. Christy, “Optical constants of the noble metals,” Phys. Rev. B 6(12), 4370–4379 (1972). [CrossRef]
26. L. Lajaunie, F. Boucher, R. Dessapt, and P. Moreau, “Strong anisotropic influence of local-field effects on the dielectric response of α-MoO3,” Phys. Rev. B 88(11), 115141 (2013). [CrossRef]
27. E. D. Palik, ed., Handbook of Optical Constants of Solids (Academic, 1998).
28. S. P. Caigas, S. R. M. Santiago, T. N. Lin, C. A. J. Lin, C. T. Yuan, J. L. Shen, and T. Y. Lin, “Origins of excitation-wavelength-dependent photoluminescence in WS2 quantum dots,” Appl. Phys. Lett. 112(9), 092106 (2018). [CrossRef]
29. A. F. van Driel, I. S. Nikolaev, P. Vergeer, P. Lodahl, D. Vanmaekelbergh, and W. L. Vos, “Statistical analysis of time-resolved emission from ensembles of semiconductor quantum dots: Interpretation of exponential decay models,” Phys. Rev. B 75(3), 035329 (2007). [CrossRef]
30. T. L. Shen, H. W. Hu, W. J. Lin, Y. M. Liao, T. P. Chen, Y. K. Liao, T. Y. Lin, and Y. F. Chen, “Coherent Förster resonance energy transfer: A new paradigm for electrically driven quantum dot random lasers,” Sci. Adv. 6(41), eaba1705 (2020). [CrossRef]
31. A. Panniello, M. Trapani, M. Cordaro, C. N. Dibenedetto, R. Tommasi, C. Ingrosso, E. Fanizza, R. Grisorio, E. Collini, A. Agostiano, M. L. Curri, M. A. Castriciano, and M. Striccoli, “High-efficiency FRET processes in BODIPY-Functionalized quantum dot architectures,” Chem. - Eur. J. 27, 2371–2380 (2021). [CrossRef]
32. J. Cao, H. Zhang, X. Pi, D. Li, and D. Yang, “Enhanced photoluminescence of silicon quantum dots in the presence of both energy transfer enhancement and emission enhancement mechanisms assisted by the double plasmon modes of gold nanorods,” Nanoscale Adv. 3(16), 4810–4815 (2021). [CrossRef]
33. R. Deshmukh, S. Biehs, E. Khwaja, T. Galfsky, G. S. Agarwal, and V. M. Menon, “Long-range resonant energy transfer using optical topological transitions in metamaterials,” ACS Photonics 5(7), 2737–2741 (2018). [CrossRef]
34. W. D. Newman, C. L. Cortes, A. Afshar, K. Cadien, A. Meldrum, R. Fedosejevs, and Z. Jacob, “Observation of long-range dipole-dipole interactions in hyperbolic metamaterials,” Sci. Adv. 4(10), eaar5278 (2018). [CrossRef]
35. J. M. Steele, C. M. Ramnarace, and W. R. Farner, “Surface plasmon enhanced FRET,” Proc. of SPIE. 10353, 103530U (2017). [CrossRef]
36. S. Kumar, N. Agrawal, C. Saha, and R. Jh, Optical Fiber-based Plasmonic Biosensors (CRC, 2022).
37. S. T. Kochuveedua and D. H. Kim, “Surface plasmon resonance mediated photoluminescence properties of nanostructured multicomponent fluorophore systems,” Nanoscale 6(10), 4966–4984 (2014). [CrossRef]
38. C. Ma, Z. Zhang, T. Tan, and J. J. Zhu, “Recent Progress in Plasmonic based Electrochemiluminescence Biosensors: A Review,” Biosensors 13(2), 200 (2023). [CrossRef]
39. C. C. Wang, M. Kataria, H. I. Lin, A. Nain, H. Y. Lin, C. R. P. Inbaraj, Y. M. Liao, A. Thakran, H. T. Chang, F. G. Tseng, Y. P. Hsieh, and Y. F. Chen, “Generation of silver metal nanocluster random lasing,” ACS Photonics 8(10), 3051–3060 (2021). [CrossRef]
