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Towards Pressure Sensors Based on Polymer Planar Bragg Gratings

  • While Bragg grating-based optical devices have shown promising performances for pressure sensing applications, their sensitivity, especially in the low-pressure regime, is unsatisfying and needs to be optimized by elaborate designs, such as cantilevers or other extrinsic mechanical transducers. This contribution demonstrates and discusses a novel concept for optical pressure sensors based on polymer planar Bragg gratings. Waveguide and Bragg grating are fabricated underneath the surface of a temperature-stable and humidity-insensitive cyclic olefin copolymer substrate by means of a femtosecond laser. Based on the employed direct-writing procedure, in combination with adaptive, in-situ beam shaping with a spatial light modulator, writing depth, i.e., location of the photonic structures within the substrate, as well as Bragg grating periodicity and positioning can be deliberately chosen. Afterwards, the polymer substrate is post-processed with a high-precision micro mill, so a diaphragm comprising the integrated photonic structures is generated. The resulting diaphragm exhibits a thickness of 300 µm and a diameter of 10 mm. Finally, the optical sensor is packaged and sealed to form an air-filled gas pocket underneath the diaphragm. Deformations of the diaphragm by external pressure changes translate to strain variations along the waveguide axis and thus perturb the Bragg grating period. This leads to changes in the grating’s wavelength of main reflection, which can be evaluated in order to quantify the relative external pressure. With this straightforward optical sensor concept, pressure sensitivities up to 39 pm kPa-1, within relative pressures ranges from 78 kPa to 372 kPa, are achieved.
Metadaten
Author:Stefan KeferORCiD, Natalie Pape, Nikola Gries, Gian-Luca Roth, Bernhard SchmaussORCiD, Ralf HellmannORCiD
DOI:https://doi.org/10.1117/12.2648723
ISBN:9781510659414
Parent Title (English):Organic Photonic Materials and Devices XXV
Document Type:Conference Proceeding
Language:English
Year of Completion:2023
Release Date:2023/03/22
Tag:Bragg grating; cyclic olefin copolymers; femtosecond laser; integrated photonics; pressure sensor
GND Keyword:Bragg-Reflektor; Drucksensor
Urheberrecht:1
Institutes:Fakultät Ingenieurwissenschaften / Labore / Angewandte Lasertechnik und Photonik (alp)
research focus :Materials / Material Testing & Sensor Technology
Licence (German):Keine Lizenz - es gilt das deutsche Urheberrecht
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