About Time: Observation of Time-Reflection at Optical Frequencies
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arXiv
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| Format: | Preprint |
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2026
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| author | Segal, Ohad Konforty, Noa Schiller, Oded Tolchin, Maxwell J. Yasniger, Tony Birk, Michael Palatnik, Alexander Saha, Soham Sidorenko, Pavel Maria, Jon-Paul Plotnik, Yonatan Segev, Mordechai |
| author_facet | Segal, Ohad Konforty, Noa Schiller, Oded Tolchin, Maxwell J. Yasniger, Tony Birk, Michael Palatnik, Alexander Saha, Soham Sidorenko, Pavel Maria, Jon-Paul Plotnik, Yonatan Segev, Mordechai |
| contents | Time-reflection occurs when a wave is propagating in a medium undergoing a large and abrupt change in its properties: the original wave splits into a time-refracted wave and a time-reflected wave, each displaying different features. The time-refracted wave continues along its original course but experiences a frequency shift, whereas the time-reflected wave is propagating backwards in space with a reversed phase, also with a shifted frequency. These phenomena are fundamental to any wave system, but the most interesting are electromagnetic (EM) waves, specifically at optical frequencies, where they can couple to light-matter interactions. However, time-reflection of EM waves was thus far observed only at RF frequencies, never at optical frequencies. This is because time-reflection requires an order-unity variation of the refractive index occurring faster than a single wave cycle, and conventional optical nonlinearities are either too weak or too slow by orders of magnitude. Here, we present the first observation of time-reflection at optical frequencies. We induce an order-unity refractive-index change with sub-cycle duration, observe the time-reflection, and study its fundamental properties. These results provide an experimental pathway to experimenting with time-interfaces, generating photonic time-crystals and exploring new regimes of light-matter interaction in time-varying media. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2605_15632 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | About Time: Observation of Time-Reflection at Optical Frequencies Segal, Ohad Konforty, Noa Schiller, Oded Tolchin, Maxwell J. Yasniger, Tony Birk, Michael Palatnik, Alexander Saha, Soham Sidorenko, Pavel Maria, Jon-Paul Plotnik, Yonatan Segev, Mordechai Optics Time-reflection occurs when a wave is propagating in a medium undergoing a large and abrupt change in its properties: the original wave splits into a time-refracted wave and a time-reflected wave, each displaying different features. The time-refracted wave continues along its original course but experiences a frequency shift, whereas the time-reflected wave is propagating backwards in space with a reversed phase, also with a shifted frequency. These phenomena are fundamental to any wave system, but the most interesting are electromagnetic (EM) waves, specifically at optical frequencies, where they can couple to light-matter interactions. However, time-reflection of EM waves was thus far observed only at RF frequencies, never at optical frequencies. This is because time-reflection requires an order-unity variation of the refractive index occurring faster than a single wave cycle, and conventional optical nonlinearities are either too weak or too slow by orders of magnitude. Here, we present the first observation of time-reflection at optical frequencies. We induce an order-unity refractive-index change with sub-cycle duration, observe the time-reflection, and study its fundamental properties. These results provide an experimental pathway to experimenting with time-interfaces, generating photonic time-crystals and exploring new regimes of light-matter interaction in time-varying media. |
| title | About Time: Observation of Time-Reflection at Optical Frequencies |
| topic | Optics |
| url | https://arxiv.org/abs/2605.15632 |