Observation of wave amplification and temporal topological state in a genuine photonic time crystal
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arXiv
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| Main Authors: | , , , , , , , , |
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| Format: | Preprint |
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2025
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| _version_ | 1866908431571484672 |
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| author | Xiong, Jiang Zhang, Xudong Duan, Longji Wang, Jiarui Long, Yang Hou, Haonan Yu, Letian Zou, Linyang Zhang, Baile |
| author_facet | Xiong, Jiang Zhang, Xudong Duan, Longji Wang, Jiarui Long, Yang Hou, Haonan Yu, Letian Zou, Linyang Zhang, Baile |
| contents | Photonic time crystals (PTCs) are materials whose dielectric permittivity is periodically modulated in time, giving rise to bandgaps not in energy-as in conventional photonic crystals-but in momentum, known as k-gaps. These k-gaps enable wave amplification by extracting energy from temporal modulation, offering a mechanism for coherent light generation that bypasses traditional optical gain. PTCs also extend the concept of topological insulators to the time domain, inducing a temporal topological state at the mid-gap of the k-gap, characterized by the Zak phase-a topological invariant originally defined for spatial lattices. Here, we experimentally demonstrate the properties of a k gap in a genuine PTC, realized in a dynamically modulated transmission-line metamaterial. Wave amplification within the k-gap is observed, with an initial power spectrum narrowing and shifting toward the gap. To probe the mid-gaptopological state, we introduce a temporal interface separating two PTCs with distinct topological phases. The measured phase shift between time-reflected and time-refracted waves, together with the temporal confinement of the topological state, provides direct evidence of nontrivial temporal topology. By integrating kgap amplification with time-domain topological features, our work opens new avenues for light generation and manipulation in time-varying photonic materials. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2507_02223 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Observation of wave amplification and temporal topological state in a genuine photonic time crystal Xiong, Jiang Zhang, Xudong Duan, Longji Wang, Jiarui Long, Yang Hou, Haonan Yu, Letian Zou, Linyang Zhang, Baile Optics Quantum Physics Photonic time crystals (PTCs) are materials whose dielectric permittivity is periodically modulated in time, giving rise to bandgaps not in energy-as in conventional photonic crystals-but in momentum, known as k-gaps. These k-gaps enable wave amplification by extracting energy from temporal modulation, offering a mechanism for coherent light generation that bypasses traditional optical gain. PTCs also extend the concept of topological insulators to the time domain, inducing a temporal topological state at the mid-gap of the k-gap, characterized by the Zak phase-a topological invariant originally defined for spatial lattices. Here, we experimentally demonstrate the properties of a k gap in a genuine PTC, realized in a dynamically modulated transmission-line metamaterial. Wave amplification within the k-gap is observed, with an initial power spectrum narrowing and shifting toward the gap. To probe the mid-gaptopological state, we introduce a temporal interface separating two PTCs with distinct topological phases. The measured phase shift between time-reflected and time-refracted waves, together with the temporal confinement of the topological state, provides direct evidence of nontrivial temporal topology. By integrating kgap amplification with time-domain topological features, our work opens new avenues for light generation and manipulation in time-varying photonic materials. |
| title | Observation of wave amplification and temporal topological state in a genuine photonic time crystal |
| topic | Optics Quantum Physics |
| url | https://arxiv.org/abs/2507.02223 |