Towards photonic time-crystals: observation of a femtosecond time-boundary in the refractive index

Lustig, Eran; Saha, Soham; Bordo, Eliyahu; DeVault, Clayton; Chowdhury, Sarah N.; Sharabi, Yonatan; Boltasseva, Alexandra; Cohen, Oren; Shalaev, Vladimir M.; Segev, Mordechai

doi:10.1364/cleo_qels.2021.ff2h.1

Cited by 14 publications

(12 citation statements)

References 8 publications

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“…For light in the near infrared, the modulation should be at few femtosecond rates with an absolute permittivity change of De > 0.1, which is difficult to realize in experimental conditions. However, recent progress with epsilon-nearzero materials (21)(22)(23)(24) brings these ideas close to experimental realization (25).…”

mentioning

confidence: 98%

Amplified emission and lasing in photonic time crystals

Lyubarov

Lumer

Dikopoltsev

et al. 2022

Science

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Photonic time crystals – materials whose dielectric permittivity is modulated periodically in time – offer new concepts in light manipulation. We study theoretically the emission of light from a radiation source placed inside a photonic time crystal, and find that radiation corresponding to the momentum band gap is exponentially amplified, whether initiated by a macroscopic source, an atom, or by vacuum fluctuations, drawing the amplification energy from the modulation. The radiation linewidth becomes narrower with time, eventually shrinking to the middle of the bandgap, which enables to propose the concept of non-resonant tunable photonic time-crystal laser. Finally, we find that the spontaneous decay rate of an atom embedded in a photonic time-crystal vanishes at the band edge due to low density of photonic states.

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confidence: 98%

Amplified emission and lasing in photonic time crystals

Lyubarov

Lumer

Dikopoltsev

et al. 2022

Science

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“…This allows for ultra-sharp changes in the refractive index upon light absorption (Fig. 2b), which can result in large frequency shifts [34,35], with the potential to achieve timereflection [36] under a fast-enough change. In such interband processes the bottleneck is the relaxation speed.…”

Section: Ultrafast Index Changementioning

confidence: 99%

Photonic time crystals: A materials perspective

Shalaev¹,

Saha²,

Segal³

et al. 2023

Preprint

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Recent advances in ultrafast, large-modulation photonic materials have opened the door to many new areas of research. One specific example is the exciting prospect of photonic time crystals. In this perspective, we outline the most recent material advances that are promising candidates for photonic time crystals. We discuss their merit in terms of modulation speed and depth. We also investigate the challenges yet to be faced and provide our estimation on possible roads to success.

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“…Direct manipulations of the time boundaries may lead to many opportunities, such as photonic time crystals [7,[9][10][11][12] and Floquet metamaterials [13,14]. Despite the intriguing directions, the observation of time boundary effects requires a large and rapid enough change in the refractive index, which is extremely challenging in optical materials [15,16]. Until recently, the time refraction has been observed at the optical frequency [6,15] and the time reflection has only been reported in the classical waterwave [17] and transmission-line systems [18].…”

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confidence: 99%

“…Despite the intriguing directions, the observation of time boundary effects requires a large and rapid enough change in the refractive index, which is extremely challenging in optical materials [15,16]. Until recently, the time refraction has been observed at the optical frequency [6,15] and the time reflection has only been reported in the classical waterwave [17] and transmission-line systems [18]. The lack of experimental realization leaves the investigation of various temporal boundary effects largely unexplored.…”

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confidence: 99%

Quantum time reflection and refraction of ultracold atoms

Dong¹,

Li²,

Wan³

et al. 2023

Preprint

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Time reflection and refraction are temporal analogies of the spatial boundary effects derived from Fermat's principle. They occur when classical waves strike a time boundary where an abrupt change in the properties of the medium is introduced. The main features of time-reflected and refracted waves are the shift of frequency and conservation of momentum, which offer a new degree of freedom for steering extreme waves and controlling phases of matter. The concept was originally proposed for manipulating optical waves more than five decades ago. However, due to the extreme challenges in the ultrafast engineering of the optical materials, the experimental realization of the time boundary effects remains elusive. Here, we introduce a time boundary into a momentum lattice of ultracold atoms and simultaneously demonstrate the time reflection and refraction experimentally. Through launching a Gaussian-superposed state into the Su-Schrieffer-Heeger (SSH) atomic chain, we observe the time-reflected and refracted waves when the input state strikes a time boundary. Furthermore, we detect a transition from time reflection/refraction to localization with increasing strength of disorder and show that the time boundary effects are robust against considerable disorder. Our work opens a new avenue for future exploration of time boundaries and spatiotemporal lattices, and their interplay with non-Hermiticity and many-body interactions.

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Towards photonic time-crystals: observation of a femtosecond time-boundary in the refractive index

Abstract: We demonstrate experimentally a time-boundary for photons in a dielectric medium, analogous to a spatial boundary. Such abrupt temporal changes in the permittivity are necessary for observing time-reflections, photonic time-crystals and momentum bandgaps.

Cited by 14 publications

References 8 publications

Amplified emission and lasing in photonic time crystals

Amplified emission and lasing in photonic time crystals

Photonic time crystals: A materials perspective

Quantum time reflection and refraction of ultracold atoms

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