Photonic time-crystals - fundamental concepts [Invited]

Abstract

Photonic Time-Crystals (PTCs) are materials in which the refractive index varies periodically and abruptly in time. This medium exhibits unusual properties such as momentum bands separated by gaps within which waves can be amplified exponentially, extracting energy from the modulation. This article provides a brief review on the concepts underlying PTCs, formulates the vision and discusses the challenges.

Roadmap for Optical Metasurfaces

“…154 One promising avenue of research where optical switching may still make a breakthrough is the demonstration of photonic time-crystals, which, when implemented, will open new directions in tunable lasing, the study of dynamic Casimir effects, and the realization of yet unexplored quantum light−matter interaction. 224,225 Another area where novel and robust metals and dielectrics are showing promise is the field of high-harmonic generation. 226 While most XUV and high-harmonic sources rely on bulky gas lines as the source of high-energy photons, recent demonstrations of solid-state high-harmonic generation in dielectrics and metals have opened the pathway to high-energy XUV photons from plasmonics and metasurface-enabled sources.…”

“…However, the ultrasharp and fast changes enabled by optical modulation have opened new areas in polarization switching and optical isolator design . One promising avenue of research where optical switching may still make a breakthrough is the demonstration of photonic time-crystals, which, when implemented, will open new directions in tunable lasing, the study of dynamic Casimir effects, and the realization of yet unexplored quantum light−matter interaction. , …”

Bandgap engineering and amplification in photonic time crystals

“…In PTCs, the n varies periodically in time and this variation is generated by an external agency, which is the driver system. The extra energy supplied to the propagating pulse is drawn from the modulation [20]. This kind of pulse amplification in PTCs is fundamentally different from optical parametric amplification due to the non-resonant nature of amplification [3,4,12].…”

“…Time reflection and refraction of the propagating pulse in the optical regime require a sudden and abrupt periodic change in n that leads to the formation of significant k-gaps. While achieving gap propagation, the strong interference between these periodically reflected and transmitted pulses gives rise to eigenmodes with pairs of imaginary Floquet frequencies, one of which results in an amplification of the pulse [11,20].…”

A 1064 nm laser adaptive limiter with visible light transparency based on one dimensional photonic crystals of LiNbO3 defects

“…Over the past decade, photonic crystals have been extensively researched and employed in advanced devices due to their capacity to manipulate light propagation through the photonic bandgap. 17–20 Compared with two and three dimensional photonic crystals, one dimensional photonic crystals have been used in a wide range of applications such as optical sensors, optical switches, optical limiters, temperature sensors, and omni-directional high reflectors owing to their facile fabrication. 21–24 One dimensional photonic crystals, when employed as optical limiters, are nanoscale periodic optical structures capable of controlling and manipulating light, similar to the way semiconductors control electrons.…”