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Investigations on mechanical stability of laser machined optical fibre tips for medical application

  • Light delivery is a challenging task, when it comes to medical applications. The light is guided through optical fibers from the light source towards the treatment region. In case of interstitial light application, the light has to be decoupled from the fibre and spread to the surrounding tissue. To reach larger tissue volumes, this can be either obtained by adding a scattering volume to the tip of the fibre, or by directly modifying the optical fibre itself in order to break the total reflection within the fibre core. Such modifications can be either on the fibre surface itself or internally in the fibre core. One approach to obtain the fibre structuring could be laser induced surface roughening using an ultrafast laser source. While using volume scattering as diffusor at the fibre tip is currently the gold standard for non-thermal applications (< 0.3W/cm), the decoupling of high power laser intensities for thermal treatment options is still challenging. Structuring the fibre core itself usually is related with a loss of mechanical stability. As fibre breakage and potential loss within the human body can have serious consequences, the mechanical stability is one of the quality criterion in diffuser manufacturing. Therefore, investigations about the mechanical stability of laser manufactured optical fibre diffusers are needed. In order to evaluate the mechanical stability, a 4-point as well as a 2-point breaking test were developed. Different fibre diffusers, based on volume or surface scattering, were manufactured using fs-laser ablation techniques and its breaking strengths were investigated. It could be shown that for surface fibre modifications, the mechanical stability reduces with increasing defect depth. The stability significantly drops when the laser ablation was performed in the thermal energy range. Volume scattering modified fibres only showed a slight reduction in stability compared to un-machined fibres. In conclusion, internal fibre modification seems to be the most promising method to establish optical fibre diffusers, which are capable of several watts of emission power, while preserving its mechanical strength.

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Author:Stephan Ströbl, Felix Wäger, Matthias Domke, Ronald Sroka
Parent Title (German):V Summer School “Photonics meets Biology”. 16-20 September 2019. Venue: FORTH, Heraklion, Crete, Greece. Student Abstracts
Document Type:Conference Proceeding
Year of publication:2019
Contributing Corporation:FORTH, Foundation for Research and Technology - Hellas
Release Date:2020/01/28
Number of pages:1
First Page:13
Organisationseinheit:Forschung / Forschungszentrum Mikrotechnik
Publicationlist:Domke, Matthias
Ströbl, Stephan
Bibliographie 2019