Tunable Bulk Polymer Planar Bragg Gratings Electrified via Femtosecond Laser Reductive Sintering of CuO Nanoparticles

Kefer, Stefan; Bischoff, Kay; Roth, Gian‐Luca; Haubner, Julian; Schmauß, Bernhard; Hellmann, Ralf

doi:10.1002/adom.202002203

Cited by 15 publications

(16 citation statements)

References 56 publications

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“…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 ]. COC-based systems for contactless dielectrophoresis [ 18 ], protein separation [ 19 ], H

sensing [ 20 ], or a dye laser [ 21 ] have been, amongst others, implemented so far.…”

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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sensing [ 20 ], or a dye laser [ 21 ] have been, amongst others, implemented so far.…”

Section: Introductionmentioning

confidence: 99%

UV-Femtosecond-Laser Structuring of Cyclic Olefin Copolymer

et al. 2022

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“…Alternatively, femtosecond laser direct writing processes can omit birefringence effects completely, as they allow the fabrication of photonic structures deeper within the volume of the substrate. Consequently, this fabrication method is preferred if the target application does not necessitate near-surface structures, as in the case of devices that interact with sensitization coatings [ 12 , 13 ].…”

Section: Resultsmentioning

confidence: 99%

“…Based on these advantages, a multitude of photonic devices based on planar COC substrates have been developed throughout recent years. The most prominent examples include temperature sensors capable of evaluating temperatures up to 160 °C [ 9 ], multi-dimensional strain or shape sensors [ 10 ], electro-optic and optofluidic devices [ 11 , 12 ], hypersensitive hydrogen detectors [ 13 ], refractive index sensors [ 14 ] and lab-on-a-chip devices [ 15 ].…”

Section: Introductionmentioning

confidence: 99%

Birefringence in Injection-Molded Cyclic Olefin Copolymer Substrates and Its Impact on Integrated Photonic Structures

Kefer,

Limbach,

Pape

et al. 2024

Polymers

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This contribution quantifies the birefringence within injection-molded cyclic olefin copolymer plates and discusses its impact on the mechanical properties of the plates. It also focuses on the impact of birefringence on integrated waveguides and Bragg gratings and provides fabrication guidelines for such structures. The anisotropy in all three dimensions of the workpiece is examined by means of polarimetry and a prism coupler. It is found that the birefringence is inhomogenously distributed within the workpieces, whereas the maximum birefringence not only varies locally, but also depends on the observation direction. Overall, a maximum birefringence of 10 × 10−4 is found at the plate’s surface near the injection gate. The anisotropy then reduces exponentially towards the center of the workpiece and saturates at 1.8 × 10−4, in a depth of 0.4 mm. Thus, the birefringence strongly affects near-surface photonic structures. It is found that, depending on their orientation and the local birefringence of the substrate, waveguides and Bragg gratings fabricated with comparable parameters behave completely differently in terms of polarization-dependent optical attenuation, cross-sectional intensity distribution and Bragg reflection signal. For example, the support of the TM mode can vary between total loss and an optical attenuation of 0.9 dB × cm−1. In consequence, this study underlines the importance of quantifying the birefringent state of an injection-molded cyclic olefin copolymer workpiece if it is supposed to serve as a substrate for integrated photonic structures. The study furthermore demonstrates that birefringence effects can be omitted by burying the photonic structures deeper into the volume of the thermoplastic.

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“…Besides the fact that, in comparison with polymer optical fibers, planar substrates enable utilization of COC grades with higher temperature stability, handling and post-processing of planar devices is straightforward, while injection-molded substrates are also reasonably priced if they are manufactured in large quantities. Furthermore, the inherent robustness of COC substrates enables the harsh-environment application of these devices and also their subsequent electrification via femtosecond laser-based sintering JLT-33072-2023 2 processes [16], [17]. Additionally, COC is hemocompatible and the feasibility of merging integrated photonics with microfluidics on a single COC platform is already proven, thus paving the way towards COC-based lab-on-a-chip devices [18], [19].…”

Section: Introductionmentioning

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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Tunable Bulk Polymer Planar Bragg Gratings Electrified via Femtosecond Laser Reductive Sintering of CuO Nanoparticles

Cited by 15 publications

References 56 publications

UV-Femtosecond-Laser Structuring of Cyclic Olefin Copolymer

UV-Femtosecond-Laser Structuring of Cyclic Olefin Copolymer

Birefringence in Injection-Molded Cyclic Olefin Copolymer Substrates and Its Impact on Integrated Photonic Structures

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

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