Fibre Coupled Photonic Crystal Cavity Arrays on Transparent Substrates for Spatially Resolved Sensing

Mark Scullion,Thomas Krauss,Matthias Fischer

doi:10.3390/photonics1040412

Abstract

We introduce a photonic crystal cavity array realised in a silicon thin film and placed on polydimethlysiloxane (PDMS) as a new platform for the in-situ sensing of biomedical processes. Using tapered optical fibres, we show that multiple independent cavities within the same waveguide can be excited and their resonance wavelength determined from camera images without the need for a spectrometer. The cavity array platform combines sensing as a function of location with sensing as a function of time.

Highlights

Photonic waveguide structures such as ring resonators [1,2,3], slot waveguides [4] and photonic crystals [5,6,7,8,9] have shown promise as sensors for “lab-on-a-chip” style applications due to their combination of small size and high sensitivity
The photonic crystal cavity array platform we introduce here meets all of these requirements
Photonic crystals are small enough that multiple independent cavities can be combined in the same structure, with spacing on the order of a few microns

Summary

Introduction

Photonic waveguide structures such as ring resonators [1,2,3], slot waveguides [4] and photonic crystals [5,6,7,8,9] have shown promise as sensors for “lab-on-a-chip” style applications due to their combination of small size and high sensitivity These devices are chip-based, which limits their use to laboratory-based applications. It is very desirable to develop sensors that can measure living cells and tissue in-situ, in order to monitor biomedical processes directly Such in-situ sensors need to be small, flexible and able to directly interface to an optical fibre, such that the fibre becomes the limiting factor of the device size, not the chip. By using a tuneable laser on the input side, we remove the need for a spectrometer thereby highlighting that the platform, despite its novel functionality, is intrinsically very simple

Photonic Crystal Fabrication and PDMS Transfer

Tapered Fibre Fabrication

Photonic Crystal Arrays and Refractive Index Sensitivity Measurements

Coupling to Photonic Crystal via Tapered Fibres on SOI

Photonic Waveguides Transferred to PDMS

Conclusions