Metamaterial induced transparency (MIT) has great potential in photonic device applications. Here, we design a metastructure with MIT effect generated by destructive interference of bright-dark-dark three modes. Therein, the cross resonator formed by the combination of the cut-wire resonator and the long vertical metal bar (LVMB) act as the bright mode, and two pairs of split ring resonators of different lengths are distributed around the cross resonator as two dark modes, realizing significant multi-band MIT effect. Furthermore, the embedded photosensitive Si island in the broken LVMB can be used to tune the effective length by changing the conductivity, thereby actively controlling the conversion from multi-band behaviors into triple MITs. Our results could achieve the dynamic multi-band switching, which has broad application prospects for optical information processing and communication.
Terahertz metamaterials with electromagnetically induced transparency (EIT) have attracted extensive attention recently due to the broad application prospects in communication, optical storage, slow light effect, and biosensing. Here, we have studied the EIT effect caused by the interlayer coupling of two asymmetric split ring resonators with four gaps. The upper and the lower layers spaced by the intermediate Si have the same metastructures with the rotated angle of 90° to each other. By varying the length of the metallic arm, we find that the EIT effect becomes increasingly apparent as the asymmetry coefficient decrease. The simulation results indicate that with the increase of the thickness of Si layer, the EIT phenomenon will first emerge, gradually become the strongest with the thickness of 5μm, and finally tend to be weakened after further increasing the Si thickness. Meanwhile, the frequency of the transparency peak exhibits redshift with the Si thickness. It is also found that the EIT effect can be further optimized by adjusting the microstructure width of the split ring resonators. When the asymmetry coefficient and the thickness of the intermediate layer is determined, the EIT effect becomes most obvious with the width of 3 μm, and will gradually weaken with the increase of metallic width. The transparency peak frequency presents blue shift simultaneously. Our designed metastructure could provide the optional approach to modify the EIT behaviors and play an important role in the sensors and modulators.
Optical regulation strategy with the aid of hybrid materials can significantly optimize the performance of terahertz devices so as to be used in the real world. Gold nanobipyramids (AuNBPs) with synthetical tunability to the nearinfrared band show strong local electric field enhancement, which improves the optical coupling at the interface and benefits the modulation performance of all-optical devices. Here we design AuNBPs-integrated terahertz modulators with multiple structured surfaces and indicate that introducing AuNBPs can effectively enhance their modulation depths. In particular, an ultrahigh modulation enhancement with one order of magnitude can be achieved in the AuNBPs hybrid metamaterials accompanied with the multifunctional modulation characteristics. Applying the coupled Lorentz oscillator model, the theoretical calculation suggests that the optical regulation with AuNBPs originates from increased damping rate and higher coupling coefficient under pump excitation. With the help of excellent modulation enhancement in the AuNBPs integrated metastructures, a prototype of novel spatial light modulator is constructed. As a novel terahertz photonic device with the low-power consumption and multifunctionality, this modulator is promising for the potential application in spatial and frequency selective imaging.
Electromagnetically induced transparency (EIT) can be analogically achieved by terahertz (THz) metamaterial, which has extensive applications in sensing, filtering, and slow light devices. Here, we firstly construct a metastructure that can modulate THz transmission, consisting of an outer symmetrical split ring resonator (SRR) embedded with two inner closed ring resonators. The simulated THz transmission spectrum presents a simple lineshape superposition of two resonances, corresponding to the low frequency dipole mode at 1.184 THz from the external SRR and the high frequency dipole mode at 1.757 THz from the closed ring resonators, respectively. However, the EIT phenomenon can be observed by replacing the inner part with two asymmetric split ring resonators. We have attributed this to that the inner metastructure can induce an extremely weak LC resonance at 1.074 THz due to the breaking of structure asymmetry. This mode will couple with the above dipole resonance of the outer SRR to accomplish the EIT effect through the near-field coupling of the weakly accessible bright-mode and the strongly excited bright-mode in this system. By varying different parameters, we have found that the impact of the rings distance on the EIT effect is more obvious. To further modulate the EIT window, the semiconductor silicon was placed at the opening gaps of the two inner asymmetric split ring resonators. Our simulated results indicate that with the increasing of the silicon conductivity from 0 to 9000 S/m, the EIT peak will gradually weaken and finally vanish, which is consistent with the results of closed ring resonators and shows the switch on/off of EIT phenomenon. Our work provides a design approach to control the electromagnetic transparent peak and manipulate EIT effect, for the potential applications in versatile THz devices.
With strong optical response from subwavelength metamaterial structures in terahertz, plasmon-induced transparency (PIT) has attracted considerable attention in terahertz modulators and biosensing devices. Here, we tune PIT effect by the destructive interference of two bright modes. We design a terahertz metamaterials structure with triple U-shaped resonators (TUR) arrays. In the vertical direction, double U-shaped resonators (DUR) are arranged downward, single-U resonator (SUR) is upward. We change the length of the SUR, the inner arms of the DUR and the horizontal distance of the DUR in order to observe the terahertz transmission spectrum. It is found from the results that with the length of the SUR increases, the resonant frequency has an obvious red-shift, the absorption of the low-frequency resonance increases and the nonresonance absorption peak gradually decreases. As the arms of the DUR increase and the distance between them decreases in horizontal, the frequency of resonance dip has a red-shift, and the transmittance of the non-resonant region increases slightly. To explore the influence of dielectric environment on the resonance characteristics of the terahertz metamaterials, we have further performed the simulations with the applied surface analyte of different refractive index. The results show that with the increase of the refractive index of the surface of the analyte, the resonance frequency has a more significant red-shift. Our obtained results could provide the idea for designing terahertz modulators and sensitive biosensing devices.
Metamaterials has shown outstanding flexibility and functionality in optics and electromagnetics, which attracted plenty of interest. Nested ring resonators have a wide range of applications in terahertz (THz) spectroscopy, sensing and communication. Hence, we design a kind of metamaterials structure which can modulate THz transmission and resonance. It consists of a circular split ring resonator (CSRR) inside a closed square ring resonator. The single CSRR has an inductive-capacitive (LC) resonance and the single closed square ring resonator has a dipole resonance. After nesting two resonators, the resonance mode is changed from single mode to double modes. The results show that the amplitude transmission of non-resonant region is related to the gap opening and the asymmetry of structure. The amplitude transmission of resonance region depends on the conductivity of substrate. With the gap opening of CSRR increases, the amplitude transmission of non-resonant region increase. Meanwhile, the frequency of resonance has an obvious blue-shift. With the bottom edge distance of the two resonators decreases(the asymmetry increases), the amplitude transmission of the non-resonant region increases gradually and the low frequency of resonance has a red-shift and the high frequency of resonance has a blue-shift. To further analyze the influence of conductivity of substrate on amplitude transmission, we change the conductivity of substrate during the simulation. The results demonstrate that with the conductivity of the substrate increases, the resonance absorption peak decreases until disappears, the amplitude transmission of the non-resonant region decreases. Our results may have the potential applications in THz modulator.
We demonstrate the active control of resonant frequency in terahertz (THz) metamaterial comprised of split ring resonator arrays (SRRs). It is found that the introduction of different substrates can greatly modify the sensing capabilities of the SRRs structure, i.e., the SRRs designed on PET (polyethylene terephthalate) is more sensitive to THz wave accompanied with higher resonance frequency as well as wider non-resonant region. Furthermore, our simulated findings indicate that THz response sensitivity can be distinctly tuned by changing the gap of SRRs on PET. The mechanism of inductance-capacitance (LC) resonance and dipole resonance is exploited to explain the varied THz transmission responses. Our work infers that the SRRs structure based on PET with low dielectric constant is a significantly better option for biological and chemical sensing applications.
The study of terahertz band has been widely concerned, and the combination of metamaterials and various reconstruction mechanisms has made great progress in recent years. In this paper, we simulate the effect of splitting the gallium arsenide(GaAs) layer with different conductivity in the twisted split-ring resonator(SRR) pairs structure on the inductive coupling strength. We find that with the increase of the conductivity of the doped GaAs layer, the transmittance of the nonresonant region decreases, the resonance intensity decreases, and the frequency shows a blue-shift. When the conductivity increases to more than 64 S/m, the two resonant dips merge into one, and the inductive coupling gradually weakens until disappears. At the same time, we simulate the current and electric field diagram to confirm our results. Our findings are helpful to adjust the resonant intensity of metamaterials by optical pumping or DC bias in the following experiments, which improves the basic understanding of metamaterials and reconfiguration mechanisms.
Nowadays, the combination of metamaterials and molybdenum disulfide (MoS2) plays more and more important roles, due to its broad applications in many areas. Here, we propose a novel hybrid structure for terahertz (THz) wave manipulation with the integration of MoS2 layer and metamaterials consisting of split ring resonators (SRRs) arrays on Si substrate. Compared with the simulation results of single ring resonator and double ring resonators, it is found that the original dual-mode resonance transforms four mode resonance after inserting the inner ring. When the inner ring is rotated, the multi-mode resonance does not change. The resonance intensity decreases and the frequency moves to the low frequency with the red-shift effect, when MoS2 is added. The hybrid MoS2-SRRs structure THz modulator has multi-mode resonance, and the interaction between SRRs and MoS2 is revealed through the analysis of multi-mode resonance.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.