A gain route to reversed Cherenkov radiation

Area of Science:

• Physics
• Metamaterials
• Optics

Background:

• Veselago's 1968 work demonstrated reversed Cherenkov radiation in negative-index materials.
• Metamaterials research is a cornerstone of modern physics.
• Reversed Cherenkov radiation was previously thought impossible in positive-index materials.

Purpose of the Study:

• To investigate the possibility of reversed Cherenkov radiation in positive-index materials.
• To challenge the long-held belief that reversed Cherenkov radiation requires negative refractive indices.
• To explore the role of optical gain in manipulating Cherenkov radiation.

Main Methods:

• Theoretical analysis of Cherenkov radiation in homogeneous isotropic slabs.
• Exploitation of optical gain to modify radiation properties.
• Identification of precise conditions for reversed Cherenkov radiation.

Main Results:

• Reversed Cherenkov radiation observed from a positive-index isotropic slab.
• Conditions identified for maintaining backward-propagating radiation while suppressing forward-propagating radiation.
• Reversed Cherenkov radiation intensity and angular spread shown to be robust to slab thickness.

Conclusions:

• Optical gain enables reversed Cherenkov radiation in positive-index materials, contradicting prior assumptions.
• The phenomenon's robustness to slab thickness offers practical advantages.
• Increasing optical gain can decrease intensity but increase angular spread of reversed Cherenkov radiation.