Sapphire Photonic Crystal Waveguides with Integrated Bragg Grating Structure

Kefer, Stefan; Roth, Gian‐Luca; Zettl, Julian; Schmauß, Bernhard; Hellmann, Ralf

doi:10.3390/photonics9040234

Cited by 9 publications

(2 citation statements)

References 52 publications

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“…Besides altering the guided mode's diameter, LLWGs also enable mode-shape transformation and photonic splitters. Furthermore, mainly but not solely for sensing purposes, the LLWG core can also be equipped with Bragg grating (BG) structures [26], [27]. This contribution demonstrates the fabrication of LLWGs in planar COC substrates.…”

Section: Introductionmentioning

confidence: 98%

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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Section: Introductionmentioning

confidence: 98%

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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“…Alternatively, femtosecond lasers can also be employed to fabricate depressed-cladding waveguides within the bulk of sapphire substrates. Depending on the waveguide's design, single-mode behavior was demonstrated down to wavelengths in the telecommunication regime around 1550 nm 14,15 . This contribution summarizes our recent developments on the field of femtosecond laser-based micromachining of sapphire rods towards photonic applications.…”

Section: Introductionmentioning

confidence: 99%

High-precision micromachining of sapphire towards optical waveguiding structures using femtosecond lasers

Kefer

Zettl

Schmauß

et al. 2023

Laser-Based Micro- And Nanoprocessing XVII

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While sapphire is one of the most durable materials, its properties entail that high-precision machining, especially in the sub-millimeter regime, is still challenging. This contribution demonstrates and discusses novel femtosecond laser-based micromachining approaches for the fabrication of rotational-symmetric sapphire workpieces, specifically the generation of optical fibers by means of laser lathe of sapphire rods and the practical realization of windmill fibers. In addition, volume refractive index modification in planar sapphire substrates is presented to induce photonic crystal waveguides. The micromachined structures are comprehensively examined with respect to geometric fidelity, surface roughness, refractive index modification, and potential optical waveguiding properties. All micromachining approaches are done by means of frequency-doubled or frequency-tripled femtosecond laser radiation. Different laser optical setups including laser scanning head, spatial beam profilers including a spatial light modulator and axial rotatory movement of the specimen are employed for micro structuring and in-depth refractive index modifications. In particular for laser lathe, a sophisticated scanning pattern, in combination with an incremental axial rotatory movement of the specimen, allows for the precise diameter reduction of sapphire rods with 250 µm diameter to fibers with outer diameters of 25 µm. By supporting the workpiece with a V-groove fixture, multi-mode fibers with lengths up to 20 cm can be processed with an average surface roughness of 250 nm. Additionally, an adapted ablation scanning sequence enables the first practical demonstration of sapphire windmill fibers. Furthermore, using a spatial light modulator allows for the adaption of the laser propagation properties as to enable volume refractive index modifications with free-form arrangement. Hexagonal patterns of refractive index modifications surrounding a pristine waveguide core are fabricated and single-mode waveguiding at 1550 nm is verified. Finally, the possibility of integrating Bragg gratings into this photonic waveguide type is demonstrated.

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Topology optimization of a 120° bending high temperature superconducting photonic crystal waveguide

Wang,

Liu,

Gao

et al. 2024

Results in Physics

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Sapphire Photonic Crystal Waveguides with Integrated Bragg Grating Structure

Cited by 9 publications

References 52 publications

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

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

High-precision micromachining of sapphire towards optical waveguiding structures using femtosecond lasers

Topology optimization of a 120° bending high temperature superconducting photonic crystal waveguide

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