Evaluation of femtosecond laser written diffraction grating structure in polymethyl methacrylate for strain measurement

R Sun, S Liang, P J Scully, T Li, A. Baum, S.O. Oyadiji

    Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

    Abstract

    Polymethyl methacrylate (PMMA) or perspex is of great interest as a photonic material for integrated optics, microfluidics and polymer optoelectronics due to its low processing temperature, biocompatibility and ease of injection moulding and extrusion. Gratings written into polymer optical fibre (POF) have increased strain and temperature sensitivity by 14% compared with those written in silica optical fibre. Previously reported work has optimised 3-D photonic structures in undoped, bulk PMMA using femtosecond laser writing techniques. This paper evaluates the optical properties of a diffraction grating structure in bulk PMMA, when subjected to strain and deformation. A 20 ??m period grating was written into undoped commercial grade PMMA (ICI Perspex) using a 387nm, 180fs laser at 0.8??J. A He-Ne laser beam was diffracted by the grating, and the centroids of the diffracted beams, (0 and ) were measured using a CCD array. Under compression, the periodicity of the grating was perturbed, causing angular displacement of the orders, enabling loaded stress to be measured. The measurement was complicated by deformation of the sample surface, changing the angles of incidence and diffraction of all orders. Methods of distinguishing bend or tilt from compression, and the grating behaviour under extension will be presented, enabling the performance of PMMA based devices to measure strain and temperature to be predicted and unwanted effects of environmental strain and temperature on optical properties of photonic structures in PMMA to be evaluated.
    Original languageEnglish
    Title of host publicationPhoton 08: Optics & Photonics Conference
    Place of PublicationBristol
    PublisherIOP Publishing Ltd
    Publication statusPublished - Sept 2008
    EventPhoton 08: Optics & Photonics Conference. - Heriot Watt University, Edinburgh
    Duration: 25 Aug 200829 Aug 2008

    Conference

    ConferencePhoton 08: Optics & Photonics Conference.
    CityHeriot Watt University, Edinburgh
    Period25/08/0829/08/08

    Keywords

    • PMMA
    • grating
    • diffraction
    • strain
    • polymer
    • poly methyl methacrylate
    • refractive index
    • photonic structure

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