Critical coupling vortex with grating-induced high Q-factor optical Tamm states

Area of Science:

• Photonics and optical physics.
• Condensed matter physics.
• Wave phenomena.

Background:

• Optical Tamm states are surface-bound electromagnetic modes.
• Distributed Bragg reflectors (DBRs) are periodic dielectric structures.
• Bound states in the continuum (BICs) are localized states that do not radiate energy.

Purpose of the Study:

• To investigate the conditions under which optical Tamm states transform into bound states in the continuum (BICs).
• To explore the phenomenon of critical coupling in this system.
• To analyze the spatial distribution of the reflection amplitude gradient and its relation to BICs.

Main Methods:

• Theoretical investigation of optical Tamm states.
• Analysis of dielectric gratings on DBRs.
• Application of coupled mode theory.

Main Results:

• Optical Tamm states can evolve into BICs under specific conditions.
• The transition to a BIC leads to critical coupling, resulting in zero reflectance amplitude.
• A vortex in the reflection amplitude gradient, in wavelength and angle of incidence space, is identified as the location of critical coupling.

Conclusions:

• The formation of BICs from Tamm states is a viable mechanism for achieving zero reflectance.
• The observed vortex structure in the reflection amplitude gradient provides insight into the physics of critical coupling.
• Coupled mode theory successfully explains the emergence of these optical phenomena.