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Advanced Functional Materials

Unveiling Nonlinearities of Electromagnetically Induced Transparency in a THz Metamaterial

Amit Haldar, S. S. Prabhu, Shovon Pal

Published Apr 19, 2026• 2 citations
Publisher

Abstract

ABSTRACT Electromagnetically induced transparency (EIT) in terahertz (THz) metamaterials relies on the coherent coupling between a radiative (bright) mode and a sub‐radiant (dark) mode. Understanding the dynamic interplay between the bright and dark modes is key to manipulating their mutual interference and hence the transparency. Here, we use nonlinear 2D‐THz spectroscopy to scrutinize the dynamics arising from the nonlinearities of the EIT‐like phenomenon in a metamaterial platform comprising two coupled resonators. From the temporal profiles of the nonlinear pump‐probe and photon‐echo signals, we found that the bright mode relaxation time is almost twice the time for the coherent exchange of energy between the two coupled resonators. The multi‐peak nature of the photon‐echo signal and the corresponding temporal signatures further provide a direct visualization of the interference between the dressed states that drives the transparency window in our THz metamaterial. A time‐resolved density‐matrix model accurately describes the observed features, including the cross‐peak behavior and the temporal dynamics, establishing the coherent mode coupling as the origin of the transparency window.

DOI
10.1002/adfm.75422

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Physical Review B•May 31, 2011•63 citations
ABSTRACT Electromagnetically induced transparency (EIT) in terahertz (THz) metamaterials relies on the coherent coupling between a radiative (bright) mode and a sub‐radiant (dark) mode. Understanding the dynamic interplay between the bright and dark modes is key to manipulating their mutual interference and hence the transparency. Here, we use nonlinear 2D‐THz spectroscopy to scrutinize the dynamics arising from the nonlinearities of the EIT‐like phenomenon in a metamaterial platform comprising two coupled resonators. From the temporal profiles of the nonlinear pump‐probe and photon‐echo signals, we found that the bright mode relaxation time is almost twice the time for the coherent exchange of energy between the two coupled resonators. The multi‐peak nature of the photon‐echo signal and the corresponding temporal signatures further provide a direct visualization of the interference between the dressed states that drives the transparency window in our THz metamaterial. A time‐resolved density‐matrix model accurately describes the observed features, including the cross‐peak behavior and the temporal dynamics, establishing the coherent mode coupling as the origin of the transparency window.
Electromagnetically induced transparency (EIT) in terahertz (THz) metamaterials relies on the coherent coupling between a radiative (bright) mode and a subradiant (dark) mode. Understanding the dynamic interplay between the bright and dark modes holds the key to manipulate the mutual interference and hence the transparency. Here, we use nonlinear 2D-THz spectroscopy to scrutinize the dynamics through nonlinearities of the EIT-like phenomenon in a metamaterial platform that comprises of two coupled resonators. From the temporal profiles of the nonlinear pump-probe and photon-echo signals, we found that the bright mode relaxation time is almost twice the time for the coherent exchange of energy between the two coupled resonators. The multi-peak nature of photon-echo signal and the corresponding temporal signatures further provides a direct visualization of the interference between the dressed states that drives the transparency window in our THz metamaterial. A time-resolved density matrix model accurately describes the observed features, including the cross-peak behavior and the temporal dynamics, establishing the coherent mode coupling as the origin of the transparency window.
In this Letter, we construct a metamaterial with dual-mode electromagnetically induced transparency (EIT)-like behavior by introducing "bright atoms," "quasi-dark atoms," and "dark atoms" simultaneously. The dual-mode EIT-like behavior has been demonstrated both experimentally and theoretically in terahertz (THz) regime. At two EIT-like modes, slow light is also observed as two time-delayed wave packets, and the effective group refractive index can reach 10(2). Furthermore, stable dual-mode EIT-like behavior is verified in this metamaterial for a wide range of oblique incident angles. Our work provides a design approach to mimic dual-mode EIT, and such an approach may achieve potential applications on miniaturized and versatile THz devices.
We theoretically investigate the classical analog of electromagnetically induced transparency (EIT) and electromagnetically induced absorption (EIA) in a planar metamaterial at optical frequency, which originates from destructive and constructive interference between dark and radiative elements.The metamaterial consists of two coupled resonators with different geometries.An EIT-like transparent window with low absorption is observed and found to be strongly affected by resonant states of the resonators.The transition between the EIT and EIA is achieved by changing the split width and coupling distance.The absorption is enhanced up to 2.5 times compared with the dipolar case.The excitation of the dark mode is very important for EIT-and EIA-like responses of the proposed metamaterial.The EIT and EIA phenomena offer a potential method for manipulating electromagnetic response in metamaterial-based devices.
Abstract Incorporating auxiliary all‐optical modulation speeds as optional response modes into a single metamaterial is a promising research route towards advanced terahertz (THz) applications ranging from spectroscopy and sensing to communications. Particularly, a plethora of dynamically tunable optical functionalities are determined by the resonant light‐matter interactions. Here, an electromagnetically induced transparency (EIT) resonator stacked with two traditional semiconductor films, namely silicon (Si) and germanium (Ge), is experimentally demonstrated. A giant switching feature of the EIT window with a peak at 0.65 THz occurs when the Si or Ge film is excited by ultrafast optical pulses, allowing for an optically tunable group delay of the THz wave packet. The recovery time for the slow and fast on‐off‐on switching cycles is 1.7 ns and 11 ps, respectively, which are mapped as the pump delay time of Si and Ge. Two optional response modes are integrated on the same device, where the modulation speed varies by three orders of magnitude, endowing the modulator more compact. This work provides new prospects for the design and construction of novel chip‐scale THz devices based on EIT and their applications in areas of sophisticated optical buffering and active filtering.
Electromagnetically induced transparency (EIT)-like transmission was demonstrated in terahertz asymmetric parallel plate waveguides with two identical cavities. By shifting the position of the bottom cavity from the symmetric position in the propagation direction, both the phases of the propagating wave at resonances and the coupling strengths between two cavities are changed, resulting in exciting the additional asymmetric resonance and manipulating the detuning of two different resonant frequencies. The transparent peak between two resonances comes from the cancelation of symmetric and asymmetric resonances. We also use the physical picture of excitation of quasi-dark mode to explain this EIT-like transmission, which is similar to the metamaterial systems.
Electromagnetically induced transparency (EIT) in metamaterials is studied experimentally in a waveguide system with tunable intrinsic loss. There is a window in the transmission spectrum with nearly unchanged maximum transmittance, which is the result of simultaneous suppression of reflection and absorption. Group delay measurements demonstrate the transmission-delay product is almost independent of the intrinsic loss while the bandwidth-delay product is affected. Dynamic evolution of EIT in metamaterials is also investigated and we observe parameter-controllable excitation transfer from the bright resonator to the dark resonator during the process of EIT buildup.