A fluorescence-based gas-sensor using polymer waveguides

Problem Definition:

Several gas-sensing mechanisms based on fluorescent dyes have been reported in literature: a fluorescent dye absorbs light in a certain wavelength range and emits in a different wavelength range as shown in Fig. 1. The presence of analytes, such as gasses or liquids, alters this emission spectrum, which can be detected.

Fig. 1: The principle of fluorescence; in the presence of analytes, the emission spectrum changes.

In applications like deep pipe gas-leakages, food-packaging and largely in medicine a compact foil-based flexible gas sensor would be of tremendous value. Therefore, such a sensor platform is currently being developed at the Centre for Microsystems Technology (CMST) and consists of a light source (LED, OLED, VCSEL), a photodetector, waveguide and coupling structures, all incorporated on a flexible polymer foil (see Fig.2). This research is executed in collaboration with Holst Centre (Eindhoven), a research institute focusing on inexpensive foil-based technologies. Currently, large lightguides and multimode waveguides are being used to build these sensors, but many optical sensors perform better with single-mode waveguides. This master thesis will therefore also investigate the use of single mode waveguides to develop accurate fluorescence-based gas sensors.




Fig. 2: Current gas sensor platform consisting of a light source (LED, OLED, VCSEL), a photodetector, waveguides and coupling structures (left), all incorporated on a flexible polymer foil (right). 

Objectives:

The objective of this thesis is to develop a theoretic fluorescence based sensor model using the Lumerical simulation software (http://www.lumerical.com/) which can then be fabricated in the clean rooms of CMST (Technologiepark, Zwijnaarde). Different sensor topologies will be investigated and this will include simulation of multimode and single mode waveguide sensors, evanescent field sensing, bulk sensing etc. Also, the effects of different parameters like refractive-index, impact of polarization, waveguide-geometry will be assessed.

Concretely, the work may (for example) be split up in the following aspects:
  • Selection of suited sensor materials such as fluorescent dyes, waveguide materials etc., depending on a specific gas sensing application as chosen by the candidate (literature search)
  • Design and simulation of possible sensor topologies based on simulations using Lumerical software
  • Fabrication of the proposed sensor in the cleanroom
  • Testing and evaluation of the sensor
Based on the candidate’s preferences, either the simulation part or fabrication part can be emphasized more. 

Keywords:

dye, fluorescence, gas sensors, optical, LED, waveguides, sensing, VCSEL 

Location:

Ardoyen CMST + at home.