A 1.5D Photonic Crystal Interface for Prism-Free, Near-Normal, Low-Background Photoluminescence.

Area of Science:

• Photonics
• Nanotechnology
• Biophysics

Background:

• Photonic crystal gratings (PCGs) and Bragg mirrors (PCMs) enhance photoluminescence (PL) in biosensing.
• Current methods face limitations like bulky prism coupling and high background noise, hindering integration.

Purpose of the Study:

• To demonstrate an all-dielectric PCG-PCM interface for improved fluorescence-based biosensing.
• To overcome limitations of existing PCGs and PCMs for compact and efficient systems.

Main Methods:

• Fabrication of a 1.5D photonic crystal (PC) using a TiO2 ridge-groove PCG atop a TiO2/SiO2 Bragg mirror.
• Utilizing bound states in the continuum (BICs) for enhanced PL properties.
• Employing angle-resolved spectroscopy, back-focal-plane imaging, and numerical simulations for characterization.

Main Results:

• The PCG-PCM interface demonstrated increased PL spectral flux, polarization selectivity, and near-normal outcoupling.
• The PCM effectively suppressed broadband background and improved PL extraction.
• Achieved up to a 5.2-fold improvement in signal-to-background ratio compared to standalone components.

Conclusions:

• The 1.5D PC interface offers a scalable and compact solution for high-contrast fluorescence readout.
• This technology paves the way for next-generation biosensing and bioimaging applications.
• The integrated approach overcomes previous limitations in PL enhancement for biosensors.