Hybrid polymer based Bragg grating sensors - Fundamental investigations and application (FR 713/10-2)
Third party funded individual grant
Acronym: FR 713/10-2
Start date : 01.10.2013
Project details
Short description
Within this work an optical sensor system based on Bragg-gratings is developed, aiming to enable the detection of temperature, humidity and the quantitative or qualitative analysis of gases and liquids. For the first time, Bragg gratings as integrated optical sensor elements are fabricated in hybrid polymers by using UV-enhanced inscription of the gratings through a phase mask. The sensor is based on a planar waveguide, containing a periodical modification of the refractive index in propagation direction. This modulation leads to a partial diffraction and reflection of the guided light spectrum. The reflected wavelength is depending on ambient conditions such as temperature or humidity and, therefore, allows their quantification.
By using the material class of hybrid polymers within this work, the advantages of commonly used inorganic and organic materials can be combined. For the first time, hybrid polymers are structured using substrate conformal imprint lithography (SCIL), creating waveguides and other optical structures. Compared to alternative structuring methods, multiple advantages arise from the use of SCIL, concerning process effort, the variety of usable substrates and the lateral resolution of optical structures. Another aim, besides extensive process developments concerning the fabrication of the sensors, is to investigate the sensors’ reflection signals as well as the evaluation of the usability of such sensors for different measurement applications.
Scientific Abstract
Aim of the project, entitled “Hybrid polymer based Bragg grating sensors - Fundamental investigations and application”, is the development of a new and innovative manufacturing method in order to fabricate photonic structures and devices. The novelty, from a technological perspective, is the combination of UV-enhanced substrate conformal imprint lithography (UV-SCIL) as a wafer-scale patterning technique used to imprint three-dimensional photonic structures into hybrid polymers and the UV-enhanced inscription of Bragg gratings into pre-structured elements. This combination enables a fabrication of three-dimensional photonic circuits using only two major process steps. Further on, a low surface roughness for reduced attenuation losses as well as a high accuracy of the transferred structures is expected by applying UV-SCIL. Waveguides, couplers and integrated Bragg gratings will be realized within the project. Such elements will be combined to a sensor element, which will then be qualified for sensing applications. Such fabricated devices are applicable for i.e. gas detection. Another main topic, which will be addressed within the project, is concerning material specific investigations. Chemical processes will be identified, leading to a UV-induced modification of the refractive index of hybrid polymers. Further on, the impact of humidity on photonic devices made from this material class will be analyzed. In parallel, a complete simulation of the inscription process of the Bragg gratings will be performed in order to support and round up the experimental work.