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Bar-Hillel L, Dikopoltsev A, Kam A, Sharabi Y, Segal O, Lustig E, Segev M. Time Refraction and Time Reflection above Critical Angle for Total Internal Reflection. PHYSICAL REVIEW LETTERS 2024; 132:263802. [PMID: 38996327 DOI: 10.1103/physrevlett.132.263802] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2023] [Accepted: 05/03/2024] [Indexed: 07/14/2024]
Abstract
We study the time reflection and time refraction of waves caused by a spatial interface with a medium undergoing a sudden temporal change in permittivity. We show that monochromatic waves are transformed into a pulse by the permittivity change, and that time reflection is enhanced at the vicinity of the critical angle for total internal reflection. In this regime, we find that the evanescent field is transformed into a propagating pulse by the sudden change in permittivity. These effects display enhancement of the time reflection and high sensitivity near the critical angle, paving the way to experiments on time reflection and photonic time crystals at optical frequencies.
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Affiliation(s)
| | | | | | | | - Ohad Segal
- Department of Electrical and Computer Engineering, Technion, Haifa 32000, Israel
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Zhou W, Zhu S, Zhang Z, Zhu R, Chen B, Zhao J, Wei X, Lu H, Zheng B. Time-varying metasurface driven broadband radar jamming and deceptions. OPTICS EXPRESS 2024; 32:17911-17921. [PMID: 38858959 DOI: 10.1364/oe.521602] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2024] [Accepted: 04/12/2024] [Indexed: 06/12/2024]
Abstract
Conventional radar jamming and deception systems typically necessitate the custom design of complex circuits and algorithms to transmit an additional radio signal toward a detector. Consequently, they are often cumbersome, energy-intensive, and difficult to operate in broadband electromagnetic environment. With the ongoing trend of miniaturization of various devices and the improvement of radar system performance, traditional techniques no longer meet the requirements for broadband, seamless integration, and energy efficiency. Time-varying metasurfaces, capable of manipulating electromagnetic parameters in both temporal and spatial domains, have thus inspired many contemporary research studies to revisit established fields. In this paper, we introduce a time-varying metasurface driven radar jamming and deception system (TVM-RJD), which can perfectly overcome the aforementioned intrinsic challenges. Leveraging a programmable bias voltage, the TVM-RJD can alter the spectrum distribution of incident waves, thereby deceiving radar into making erroneous judgments about the target's location. Experimental outcomes affirm that the accuracy deviation of the TVM-RJD system is less than 0.368 meters, while achieving a remarkable frequency conversion efficiency of up to 96.67%. The TVM-RJD heralds the expansion into a wider application of electromagnetic spatiotemporal manipulation, paving the way for advancements in electromagnetic illusion, radar invisibility, etc.
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Xin YH, Hu KM, Yin HZ, Deng XL, Dong ZQ, Yan SZ, Jiang XS, Meng G, Zhang WM. Dynamic Optical Encryption Fueled via Tunable Mechanical Composite Micrograting Systems. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2024; 36:e2312650. [PMID: 38339884 DOI: 10.1002/adma.202312650] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2023] [Revised: 01/18/2024] [Indexed: 02/12/2024]
Abstract
Optical grating devices based on micro/nanostructured functional surfaces are widely employed to precisely manipulate light propagation, which is significant for information technologies, optical data storage, and light sensors. However, the parameters of rigid periodic structures are difficult to tune after manufacturing, which seriously limits their capacity for in situ light manipulation. Here, a novel anti-eavesdropping, anti-damage, and anti-tamper dynamic optical encryption strategy are reported via tunable mechanical composite wrinkle micrograting encryption systems (MCWGES). By mechanically composing multiple in-situ tunable ordered wrinkle gratings, the dynamic keys with large space capacity are generated to obtain encrypted diffraction patterns, which can provide a higher level of security for the encrypted systems. Furthermore, a multiple grating cone diffraction model is proposed to reveal the dynamic optical encryption principle of MCWGES. Optical encryption communication using dynamic keys has the effect of preventing eavesdropping, damage, and tampering. This dynamic encryption method based on optical manipulation of wrinkle grating demonstrates the potential applications of micro/nanostructured functional surfaces in the field of information security.
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Affiliation(s)
- Yi-Hang Xin
- State Key Laboratory of Mechanical System and Vibration, School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Kai-Ming Hu
- State Key Laboratory of Mechanical System and Vibration, School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Hao-Zhe Yin
- State Key Laboratory of Mechanical System and Vibration, School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Xin-Lu Deng
- State Key Laboratory of Mechanical System and Vibration, School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Zhi-Qi Dong
- State Key Laboratory of Mechanical System and Vibration, School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Shu-Zhen Yan
- School of Chemistry and Chemical Engineering, State Key Laboratory for Metal Matrix Composite Materials, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Xue-Song Jiang
- School of Chemistry and Chemical Engineering, State Key Laboratory for Metal Matrix Composite Materials, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Guang Meng
- State Key Laboratory of Mechanical System and Vibration, School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Wen-Ming Zhang
- State Key Laboratory of Mechanical System and Vibration, School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China
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Michael MH, Haque SRU, Windgaetter L, Latini S, Zhang Y, Rubio A, Averitt RD, Demler E. Photonic time-crystalline behaviour mediated by phonon squeezing in Ta 2NiSe 5. Nat Commun 2024; 15:3638. [PMID: 38684735 PMCID: PMC11059354 DOI: 10.1038/s41467-024-47855-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2023] [Accepted: 04/11/2024] [Indexed: 05/02/2024] Open
Abstract
Photonic time crystals refer to materials whose dielectric properties are periodic in time, analogous to a photonic crystal whose dielectric properties is periodic in space. Here, we theoretically investigate photonic time-crystalline behaviour initiated by optical excitation above the electronic gap of the excitonic insulator candidate Ta2NiSe5. We show that after electron photoexcitation, electron-phonon coupling leads to an unconventional squeezed phonon state, characterised by periodic oscillations of phonon fluctuations. Squeezing oscillations lead to photonic time crystalline behaviour. The key signature of the photonic time crystalline behaviour is terahertz (THz) amplification of reflectivity in a narrow frequency band. The theory is supported by experimental results on Ta2NiSe5 where photoexcitation with short pulses leads to enhanced THz reflectivity with the predicted features. We explain the key mechanism leading to THz amplification in terms of a simplified electron-phonon Hamiltonian motivated by ab-initio DFT calculations. Our theory suggests that the pumped Ta2NiSe5 is a gain medium, demonstrating that squeezed phonon noise may be used to create THz amplifiers in THz communication applications.
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Affiliation(s)
- Marios H Michael
- Department of Physics, Harvard University, Cambridge, MA, 02138, USA.
- Max Planck Institute for the Structure and Dynamics of Matter, Luruper Chausse 149, 22761, Hamburg, Germany.
| | - Sheikh Rubaiat Ul Haque
- Department of Physics, University of California San Diego, La Jolla, CA, 92093, USA.
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA, 94025, USA.
| | - Lukas Windgaetter
- Max Planck Institute for the Structure and Dynamics of Matter, Luruper Chausse 149, 22761, Hamburg, Germany
| | - Simone Latini
- Max Planck Institute for the Structure and Dynamics of Matter, Luruper Chausse 149, 22761, Hamburg, Germany
| | - Yuan Zhang
- Department of Physics, University of California San Diego, La Jolla, CA, 92093, USA
| | - Angel Rubio
- Max Planck Institute for the Structure and Dynamics of Matter, Luruper Chausse 149, 22761, Hamburg, Germany
- Center for Computational Quantum Physics, The Flatiron Institute, 162 Fifth Avenue, New York, 10010, NY, USA
| | - Richard D Averitt
- Department of Physics, University of California San Diego, La Jolla, CA, 92093, USA
| | - Eugene Demler
- Department of Physics, Harvard University, Cambridge, MA, 02138, USA
- Institute for Theoretical Physics, ETH Zürich, 8093, Zürich, Switzerland
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Lin M, Ahmed S, Jamil M, Liang Z, Wang Q, Ouyang Z. Temporally-topological defect modes in photonic time crystals. OPTICS EXPRESS 2024; 32:9820-9836. [PMID: 38571207 DOI: 10.1364/oe.517616] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/03/2024] [Accepted: 02/20/2024] [Indexed: 04/05/2024]
Abstract
In this paper, we investigate the properties of temporally-topological defect modes (TTDMs) (or temporally-topological interface states) in the topological photonic time crystal (PTC) systems. The PTC systems are constructed by the cascade of multiple sub-PTCs that possess temporal inversion symmetries and different topologies. The cases of two-, three-, and multiple-sub-PTC for the topological PTC system are studied. By transfer matrix method, we find that the TTDMs appear when the topological signs of the corresponding gaps in the sub-PTCs are different. The positions of TTDMs can be adjusted by changing the modulation strength of the refractive index, the time duration, and the period of the sub-PTCs. Moreover, the number of TTDMs is one less than the number of sub-PTCs. In addition, the robustness of the systems is also studied. We find that the topological PTC systems have good robustness, especially on the random configuration of the refractive index and time duration for the temporal slabs in the systems. Such research may provide a new degree of freedom for PTC applications, such as novel PTC lasers, tunable band-stop or band-suppression PTC filters, and many others, in the field of integrated photonic circuits for optical communications.
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Zhang J, Donaldson WR, Agrawal GP. Probing the decelerating trajectory of a Raman soliton using temporal reflection. OPTICS EXPRESS 2023; 31:27621-27632. [PMID: 37710834 DOI: 10.1364/oe.497251] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/08/2023] [Accepted: 07/24/2023] [Indexed: 09/16/2023]
Abstract
Temporal reflection is a process where an optical pulse reflects off a moving boundary with different refractive indices across it. In a dispersive medium, this process creates a reflected pulse with a frequency shift that changes its speed. Such frequency shifts depend on the speed of the moving boundary. In this work, we propose and experimentally show that it is possible to probe the trajectory of the boundary by measuring the frequency shifts while changing the initial delay between the incident pulse and the boundary. We demonstrate this effect by reflecting a probe pulse off a short soliton, acting as a moving boundary that decelerates inside a photonic crystal fiber because of intrapulse Raman scattering. We deduce trajectory of the soliton from the measured spectral data for the reflected pulse.
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Pan Y, Cohen MI, Segev M. Superluminal k-Gap Solitons in Nonlinear Photonic Time Crystals. PHYSICAL REVIEW LETTERS 2023; 130:233801. [PMID: 37354410 DOI: 10.1103/physrevlett.130.233801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/12/2022] [Accepted: 04/21/2023] [Indexed: 06/26/2023]
Abstract
We propose superluminal solitons residing in the momentum gap (k gap) of nonlinear photonic time crystals. These gap solitons are structured as plane waves in space while being periodically self-reconstructing wave packets in time. The solitons emerge from modes with infinite group velocity causing superluminal evolution, which is the opposite of the stationary nature of the analogous Bragg gap soliton residing at the edge of an energy gap (or a spatial gap) with zero group velocity. We explore the faster-than-light pulsed propagation of these k-gap solitons in view of Einstein's causality by introducing a truncated input seed as a precursor of a signal velocity forerunner, and find that the superluminal propagation of k-gap solitons does not break causality.
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Affiliation(s)
- Yiming Pan
- Physics Department and Solid State Institute, Technion, Haifa 32000, Israel
- School of Physical Science and Technology and Center for Transformative Science, ShanghaiTech University, Shanghai 200031, China
| | - Moshe-Ishay Cohen
- Physics Department and Solid State Institute, Technion, Haifa 32000, Israel
| | - Mordechai Segev
- Physics Department and Solid State Institute, Technion, Haifa 32000, Israel
- Department of Electrical and Computer Engineering, Technion, Haifa 32000, Israel
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