Photonic crystal biosensor based on angular spectrum analysis

Elewout Hallynck,Peter Bienstman

doi:10.1364/oe.18.018164

Abstract

The need for cost effective and reliable biosensors in e.g. medical applications is an ever growing and everlasting one. Not only do we strive to increase sensitivity and detection limit of such sensors; ease of fabrication or implementation are equally important. In this work, we propose a novel, photonic crystal based biosensor that is able to operate at a single frequency, contrary to resonance based sensors. In a certain frequency range, guided photonic crystal modes can couple to free space modes resulting in a Lorentzian shape in the angular spectrum. This Lorentzian can shift due to refractive index changes and simulations have shown sensitivities of 65 degrees per refractive index unit and more.

Highlights

Optical biosensing is a research field that, despite already being around for quite a few years, to this day still yields a great deal of scientific output [1, 2, 3, 4, 5]
We propose a novel, photonic crystal based biosensor that is able to operate at a single frequency, contrary to resonance based sensors
In a certain frequency range, guided photonic crystal modes can couple to free space modes resulting in a Lorentzian shape in the angular spectrum

Summary

Introduction

Optical biosensing is a research field that, despite already being around for quite a few years, to this day still yields a great deal of scientific output [1, 2, 3, 4, 5] This comes as no surprise as there is and always will be a need for cost effective and reliable biosensors and this in many domains (e.g. medical, food production, military). The labels will emit light or a radiowave and depending on the intensity of the captured signal, we can determine the concentration This seems a fairly simple method, the labeling procedure of the biomolecules is quite complicated. In the sensing concept described in this paper, the incident light comes in in the plane of the PhC and is coupled out of the plane, much like a grating coupler (see Fig. 1)

Angular spectrum analysis sensor concept and simulation methods

Simulation results

Different cladding configurations

Other parameters

Noise analysis and detection limit

Conclusions