Micromilling-assisted fabrication of monolithic polymer ridge-type waveguides with integrated photonic sensing structures

Kefer, Stefan; Pape, Dominik; Roth, Gian‐Luca; Schmauß, Bernhard; Hellmann, Ralf

doi:10.1364/ome.425778

Cited by 5 publications

(6 citation statements)

References 38 publications

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“…In addition to a high optical transparency and a low water absorption, this material exhibits a high glass transition temperature, chemical resistance and proven bio-compatibility [ 2 , 3 , 4 , 5 , 6 ]. With these properties, it is superior to standard polymers such as polymethylmethacrylate (PMMA) or polycarbonate (PC), while also being compatible with economic manufacturing and processing methods such as injection molding, hot stamping [ 7 , 8 ] and micromilling [ 3 , 9 ]. Several laser-based manufacturing processes have been introduced to produce internal [ 10 ] and external [ 11 , 12 , 13 ] microfluidic channels and integrated optical elements such as waveguides or Bragg gratings [ 14 , 15 ], to electrify COC-based lab-on-chip systems [ 16 ], or to weld transparent substrates without additional absorbing layers [ 17 ].…”

Section: Introductionmentioning

confidence: 99%

UV-Femtosecond-Laser Structuring of Cyclic Olefin Copolymer

et al. 2022

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We report on the laser ablation of cyclic olefin copolymer using an amplified ultrashort pulsed laser in the ultraviolet spectral range. In addition to a high ablation depth per laser-structured layer up to 74 μm at a fluence of 22 J cm−2, an excellent mean roughness Ra of laser-patterned surfaces down to 0.5 μm is demonstrated. Furthermore, with increasing fluence, increasing ablation efficiencies up to 2.5 mm3 W−1 min−1 are determined. Regarding the quality of the ablation, we observed steep ablation flanks and low debris formation, though for fluences above 10.5 J cm−2 the formation of troughs was observed, being attributed to multiple reflections on the ablation flanks. For comparison, laser ablation was performed under identical conditions with an infrared laser wavelength. The results highlight that UV ablation exhibits significant advantages in terms of ablation efficiency, surface roughness and quality. Moreover, our results show that a larger UV focus spot accelerates the ablation process with comparable quality, paving the way for high-power UV ultrashort pulsed lasers towards an efficient and qualitative tool for the laser machining of cyclic olefin copolymer. The production of complex microfluidics further underlines the suitability of this type of laser.

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Section: Introductionmentioning

confidence: 99%

UV-Femtosecond-Laser Structuring of Cyclic Olefin Copolymer

et al. 2022

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“…The injection-molded COC samples (TOPAS 6017S-04, Topas Advanced Polymers) are cut to appropriate size by means of a desktop micro mill (CNC Mini-Mill/4, Minitech Machinery). An insight into the employed milling process and its parameters is provided in [36]. All COC substrates have a rectangular footprint with a thickness of 1.5 mm and edge lengths between 15 mm and 40 mm, in dependance of the conducted experiment.…”

Section: Fabricationmentioning

confidence: 99%

“…7 (a). The COC substrate is then mounted on the axis of the micro mill, to incrementally reduce its length in 1 mm steps with high precision and surface quality [36]. Subsequent to each length reduction step, a new physical connection between waveguide output and the respective pigtail is reestablished, before the transmission spectrum is recorded.…”

Section: B Waveguide Attenuationmentioning

confidence: 99%

Lattice-Like Waveguides With Integrated Bragg Gratings in Planar Cyclic Olefin Copolymers

Kefer,

Pape,

Bischoff

et al. 2024

J. Lightwave Technol.

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This contribution demonstrates femtosecond laser direct writing of lattice-like waveguides in planar cyclic olefin copolymer substrates. Based on numerical simulation and experimental near-field analysis, stable single-mode waveguiding around wavelengths of 1550 nm is demonstrated. The waveguiding mechanism is based on a hexagonal array of laser-induced, positive refractive index modification lines. Thus, the lateral extension of the guided mode can be adapted by varying the fabrication parameters and, in consequence, the resulting crosssectional arrangement of the refractive index perturbations. With an optical attenuation of 2.2 dB•cm -1 around 1550 nm, the fabricated waveguides are well-suited for on-chip integrated photonic devices. Moreover, the waveguides can also be equipped with Bragg gratings to enable the application of the photonic platform as a sensing device. Depending on their length, the Bragg grating structures exhibit reflectivities of up to 99% and spectral widths down to 0.3 nm. The flexibility of the fabrication process and the sensing capabilities of the lattice-like waveguides with integrated Bragg gratings are underlined by an exemplary application study demonstrating a relative pressure sensor. For that, a photonic platform is micromilled to generate a 300 µm thick diaphragm and a reference pressure chamber. The strain introduced to the diaphragm by external pressure changes can then be quantified by the integrated photonic structures. This way, absolute pressure sensitivities of up to 38 pm•kPa -1 can be achieved in a relative pressure range from -60 to 100 kPa. The newlydeveloped lattice-like waveguides with integrated Bragg gratings are therefore well-suited for the realization of novel and adaptable photonic devices and sensors.

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“…The residual material automatically serves as the pressure-sensitive diaphragm, exhibiting a thickness of 0.3 mm. More information on the employed fabrication processes, i.e., femtosecond laser fabrication of photonic structures and milling of COCs, is given by the authors elsewhere 24,25 . In the second milling step, the sensor substrate as well as the COC platelet, employed to seal the reference air pocket, are also equipped with guiding structures (see Figure 2b).…”

Section: Manufacturingmentioning

confidence: 99%

Towards pressure sensors based on polymer planar Bragg gratings

Kefer

Pape

Gries

et al. 2023

Organic Photonic Materials and Devices XXV

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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 highprecision 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 airfilled 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.

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Micromilling-assisted fabrication of monolithic polymer ridge-type waveguides with integrated photonic sensing structures

Cited by 5 publications

References 38 publications

UV-Femtosecond-Laser Structuring of Cyclic Olefin Copolymer

UV-Femtosecond-Laser Structuring of Cyclic Olefin Copolymer

Lattice-Like Waveguides With Integrated Bragg Gratings in Planar Cyclic Olefin Copolymers

Towards pressure sensors based on polymer planar Bragg gratings

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