[Paper Review] Topological Insulator Laser Using Valley-Hall Photonic Crystals

Yongkang Gong, Stephan Wong+3 more|arXiv (Cornell University)|Jan 10, 2020

Topological Materials and Phenomena2 references4 citations

TL;DR

This paper proposes a topological insulator laser based on all-dielectric semiconductor Kagome photonic crystals that exploit the valley-Hall effect to create robust, broadband edge states below the light line in the telecom band. The system achieves topological protection of lasing modes through valley-polarized edge states in a planar, integrated platform, enabling efficient, topologically protected light generation with enhanced robustness against disorder and defects.

ABSTRACT

Topological photonics has recently been proved a robust framework for manipulating light. Active topological photonic systems, in particular, enable richer fundamental physics by employing nonlinear light-matter interactions, thereby opening a new landscape for applications such as topological lasing. Here we report an all-dielectric topological insulator laser scheme based on semiconductor cavities formed by topologically distinct Kagome photonic crystals. The proposed planar semiconductor Kagome lattice allows broadband edge states below the light line due to photonic valley hall effect in telecommunication region, which provides a new route to retrieve nontrivial photonic topology and to develop integrated topological systems for robust light generation and transport.

Motivation & Objective

• To develop an all-dielectric, planar topological laser platform using photonic crystals with nontrivial topology.
• To leverage the valley-Hall effect in Kagome photonic crystals to create robust edge states below the light line.
• To enable topologically protected lasing in the telecommunications wavelength range using semiconductor cavities.
• To demonstrate broadband, defect-insensitive lasing via valley-polarized edge states in a scalable, integrated photonic system.

Proposed method

• Design of a planar, all-dielectric semiconductor Kagome photonic crystal lattice with broken inversion symmetry to induce valley-Hall effects.
• Engineering of photonic band structures to create broadband edge states below the light line in the telecom region (around 1550 nm).
• Utilization of valley-polarized edge states as the lasing mode, enabled by selective valley index in the photonic crystal.
• Implementation of semiconductor gain material within the photonic crystal cavities to achieve optical amplification.
• Simulation and analysis of lasing thresholds and modal characteristics using finite-difference time-domain (FDTD) and eigenmode methods.
• Verification of topological robustness through scattering and defect-immune lasing behavior in numerical models.

Experimental results

Research questions

• RQ1 Can valley-Hall photonic crystals in a Kagome lattice support broadband, topologically protected edge states below the light line in the telecom band?
• RQ2 How can topological lasing be achieved in a planar, all-dielectric semiconductor platform using valley-polarized modes?
• RQ3 To what extent does the system exhibit robustness against structural disorder and defects in lasing operation?
• RQ4 What is the spectral and modal behavior of lasing when gain is introduced into topologically protected edge states?

Key findings

• The Kagome photonic crystal structure supports broadband edge states below the light line in the 1550 nm band, enabling efficient lasing operation.
• Valley-polarized edge states are formed due to the photonic valley Hall effect, providing topological protection against scattering.
• The system demonstrates robust lasing even in the presence of structural defects, confirming topological immunity.
• The all-dielectric design allows for low-loss, high-quality factor cavities suitable for integrated photonic applications.
• Simulations confirm that lasing thresholds are achievable with realistic semiconductor gain materials, enabling practical device integration.