Theoretical Aspects of Photonic Time-Crystals
Abstract
Photonic Time?Crystals (PTCs) are materials in which the refractive index varies periodically and abruptly in time. When refractive index changes abruptly in time, a wave propagating in the medium experiences time?refraction and time?reflection, similar to the refraction and reflection at dielectric interfaces. However, despite the similarity, time?reflection and refraction are fundamentally different than their spatial counterparts. Namely, whereas energy (frequency) is conserved at interfaces between dielectric media, a time?interface necessarily changes the frequency, but in homogeneous media ? momentum (wavevector k) is conserved. Also, causality implies that time?reflections cannot go back in time but are back?reflected in space. Modulating the refractive index periodically in time gives rise to multiple time?reflections and time?refractions, which interfere with one another, and yield dispersion bands gapped in the momentum k (rather than in frequency, as their spatial analogues are). In PTCs energy is not conserved, hence the states residing in the momentum gap can have exponentially increasing amplitudes. (energy is drawn from the modulation) This has huge impact on the physics involved. In recent years, this research group has made foundational discoveries on light?matter interaction in PTCs.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Apr 20, 2023
- Source ID
- FA86552217256
Entities
People
- Mordechai Segev
Organizations
- Air Force Office of Scientific Research
- United States Air Force