[Paper Review] Arbitrarily polarized and unidirectional emission from thermal metasurfaces

J. Ryan Nolen, Adam Overvig+2 more|arXiv (Cornell University)|Jan 28, 2023

Metamaterials and Metasurfaces Applications9 citations

TL;DR

The paper demonstrates a single-layer metasurface that emits unidirectional, narrowband infrared thermal light with arbitrary polarization by locally tailoring photonic bound states in the continuum using geometric phase control.

ABSTRACT

Thermal emission from a hot body is ubiquitous, yet its properties remain inherently challenging to control due to its incoherent nature. Recent advances in thermal emission manipulation have been unveiling exciting phenomena and new opportunities for applications. In particular, judiciously patterned nanoscale features over their surface have been shown to channel emission sources into partially coherent beams with tailored directionality and frequency selectivity. Yet, more sophisticated forms of control, such as spin-selective and unidirectional thermal emission have remained elusive. Here, we experimentally demonstrate single-layer metasurfaces emitting unidirectional, narrowband thermal light in the infrared with arbitrary polarization states - an operation enabled by photonic bound states in the continuum locally tailored by a geometric phase controlling the temporal and spatial coherence of emitted light. The demonstrated platform paves the way to a compactification paradigm for metasurface optics, in which thermal emission or photoluminescence can feed arbitrarily patterned beams without the need of external coherent sources.

Motivation & Objective

• Motivate and enable control over incoherent thermal emission beyond conventional diffuse output.
• Show that metasurface patterning can channel thermal emission into unidirectional, polarization-tailored beams.
• Demonstrate a platform where thermal emission can be selectively steered without external coherent sources.

Proposed method

• Pattern nanoscale features on a metasurface to manipulate emission via bound states in the continuum.
• Use geometric phase control to tailor temporal and spatial coherence of emitted light.
• Experimentally demonstrate unidirectional, narrowband infrared emission with arbitrary polarization from a single-layer structure.
• Characterize how local tailoring of bound states in the continuum affects emission directionality and polarization.

Experimental results

Research questions

• RQ1 Can a single-layer metasurface achieve unidirectional thermal emission with narrow bandwidth?
• RQ2 Can arbitrary polarization states be emitted from thermal metasurfaces while maintaining directionality?
• RQ3 How do bound states in the continuum and geometric phase contribute to control over thermal emission coherence?
• RQ4 What are the practical implications for compact metasurface-based thermal emitters without external coherent sources?

Key findings

• Demonstration of unidirectional, narrowband infrared thermal emission from a thermal metasurface.
• Emission polarization can be arbitrarily chosen, enabling different polarization states.
• A photonic bound state in the continuum is locally tailored to control emission through a geometric phase mechanism.
• The approach enables patterned thermal beams without external coherent sources.