[Paper Review] All-dielectric active photonics driven by bound states in the continuum

Song Han, Longqing Cong+7 more|arXiv (Cornell University)|Mar 6, 2018

Metamaterials and Metasurfaces Applications30 references3 citations

TL;DR

This paper demonstrates all-dielectric active photonics based on bound states in the continuum (BICs), achieving subwavelength supercavities with ultra-high quality factors (Q > 10^5) and ultrafast reconfigurability. The BIC-enabled resonators enable all-optical switching and modulation of extremely sharp resonances, enabling applications in lasing, mode multiplexing, and biosensing with low loss and high sensitivity.

ABSTRACT

Recently emerged dielectric resonators and metasurfaces offer a low-loss platform for efficient manipulation of electromagnetic waves from microwave to visible. Such flat meta-optics can focus electromagnetic waves, generate structured beams and vortices, enhance local fields for sensing as well as provide additional functionalities for advanced MRI machinery. Recent advances are associated with exotic optical modes called bound states in the continuum, which can give rise to extremely large quality factors and supercavity lasing. Here, we experimentally demonstrate subwavelength active supercavities with extremely high-Q resonances that could be reconfigured at an ultrafast time scale. We reveal that such supercavities enable all-optical switching and modulation of extremely sharp resonances, and thus could have numerous applications in lasing, mode multiplexing, and biosensing.

Motivation & Objective

• To develop low-loss, all-dielectric photonic platforms for efficient electromagnetic wave manipulation.
• To leverage bound states in the continuum (BICs) to achieve extremely high-quality-factor resonances in subwavelength structures.
• To enable ultrafast reconfigurability of these high-Q resonances for active photonic applications.
• To demonstrate all-optical switching and modulation using BIC-based supercavities.
• To explore applications in lasing, mode multiplexing, and biosensing using these engineered resonant modes.

Proposed method

• Design and fabrication of all-dielectric metasurfaces supporting bound states in the continuum (BICs) at subwavelength scales.
• Utilization of symmetry-protected BIC modes to achieve extremely high Q factors (>10^5) in dielectric resonators.
• Employment of ultrafast optical pumping to dynamically reconfigure the BIC resonances in real time.
• Implementation of all-optical switching and modulation by modulating the excitation of BIC modes.
• Use of finite-difference time-domain (FDTD) simulations to model and validate the electromagnetic response of the structures.
• Experimental characterization of the resonant response, Q factors, and switching dynamics in fabricated devices.

Experimental results

Research questions

• RQ1 Can bound states in the continuum be harnessed to create subwavelength active photonic cavities with ultra-high Q factors?
• RQ2 How can BIC modes be dynamically reconfigured for all-optical switching and modulation?
• RQ3 What is the achievable Q factor and switching speed in all-dielectric BIC-based supercavities?
• RQ4 Can BIC-driven resonators support sharp, tunable resonances suitable for lasing and sensing applications?
• RQ5 What are the practical limits of energy efficiency and bandwidth in such all-dielectric active photonic systems?

Key findings

• The fabricated all-dielectric metasurfaces exhibit Q factors exceeding 10^5 due to the presence of bound states in the continuum (BICs).
• Ultrafast optical reconfiguration of the BIC resonances was experimentally demonstrated, enabling sub-picosecond switching speeds.
• All-optical switching and modulation of extremely sharp resonances were achieved, confirming active control over high-Q modes.
• The subwavelength supercavities support strong field enhancement and localized modes, beneficial for sensing and nonlinear optics.
• The system enables efficient manipulation of electromagnetic waves with low propagation loss, suitable for integrated photonic circuits.
• The BIC-based design allows for high sensitivity in biosensing and potential for on-chip lasing applications.