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Investigations on mechanical stability of laser machined optical fibre tips for medical application
(2019)
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.
Production and tribological characterization of tailored laser-induced surface 3D microtextures
(2019)
The photonic integrated circuits are required in the next generations of coherent terabit optical communications. The software tools for automated adjustment and coupling of optical fiber arrays to photonic integrated circuits has been developed. The obtained results are needed in final production phase in the technology process of photonic integrated circuits packaging.
We present design and simulation of 16-channel, 100-GHz silicon nitride based AWG using BeamPROP simulation engine of RSoft photonic tool. The AWG was designed for TM-polarized light with central wavelength of 850 nm. The input design parameters were calculated applying AWG-Parameters tool. For this purpose, we created a ridge waveguide structure, used in the design of the AWG layout, and performed FEM simulation. The output of the BPM simulation of AWG structure are the transmission characteristics, which was used to calculate transmission parameters defining optical properties of simulated AWG. The achieved simulation results are in a good agreement with the design.
Comparison of silicon nitride based 8-channel 100-GHz AWGs applying different waveguide structures
(2019)
This paper presents design and simulation of 8-channel, 100-GHz AWGs based on Si/SiO2/SiN/SiOx material platform. For the designs, two different waveguide structures were used, i.e. ridge and rib waveguides. AWGs were designed for central wavelength of 850 nm applying AWG-Parameters tool. The simulations were performed applying FEM and BPM methods in RSoft and PHASAR photonic tools. The simulation results show considerably lower losses but slightly higher channel crosstalk when applying rib waveguides.