Beam steering through dynamic gain-loss modulation

One of the major issues with active nanophotonic devices is the lack of post-fabrication dynamic control of light. The techniques employed in the literature limit large-scale integration due to the small modulation depth or the slow speed. We propose a PT-symmetric phase gradient metasurface to tune the intensity and angular response of light through dynamic material gain-loss modulation.

Phase-gradient PT-symmetric semiconductor metasurface

Our approach supports tunable asymmetric transmission for gain or loss side incidence in a vertically stacked GaInP metasurface. For loss side normal incidence, the transmission is predominantly in the 0th diffraction order (η₀ ∼ 0.80; η₁ ∼ 0.18). In contrast, for gain side incidence, an amplified transmission is observed in the 1st diffraction order (η₀ ∼ 0.04; η₁ ∼ 0.80). With increasing non-Hermiticity factor γ, the asymmetry in transmission increases. The highest asymmetry with an asymmetry factor of ∼ 0.9 is observed at λ = 655 nm. We explained the physics behind the observed asymmetry and showed an alternate path to realize on-chip reconfigurable nanophotonic devices.

Figure 2: Dynamic modulation of gain-loss in PT-symmetric phase gradient metasurface exhibits asymmetric angular response of transmission. Further details can be found in reference [1].

References

1. Jinal Kiran Tapar, Saurabh Kishen, Naresh Kumar Emani. Dynamically Tunable Asymmetric Transmission in PT-Symmetric Phase Gradient Metasurface. ACS Photonics, ASAP article (2021).