Scintillation-based fiber dosimeters are a powerful tool for minimally invasive localized real-time monitoring of the dose rate during Low Dose Rate (LDR) and High Dose Rate (HDR) brachytherapy (BT). This paper shows the design, fabrication and characterization of such dosimeters, consisting of scintillating sensor tips attached to polymer optical fiber (POF). The scintillating sensor tips consist of inorganic scintillators, dispersed in a polymer host. We present the design, fabrication and characterization of those sensor tips. The manufacturing is done by means of a custom compression and transfer moulding process implemented on a commercially available hot embossing machine. We show the manufacturing of 237 sensor tips, which are subsequently attached to the end of the POF using UV-curable adhesive. Finally, we perform dosimetry experiments in water phantoms which show a great potential for in-vivo dosimetry for brachytherapy.
We present the design and fabrication of a multicomponent optical system for LiDAR applications. The system comprises four stages: a commercial cylindrical lens, a custom freeform trilobe lens, a set of three custom reflective diffraction gratings, and a custom monolithic array of nine freeform mirrors. This optical set-up is coupled to an on-chip linear Optical Phase Array (OPA): the combination of linear beam steering provided by the OPA, and orthogonal linear steering achieved by the diffraction gratings results in a beam scan over nine directions in 3D. All the custom components have been designed and fabricated at VUB B-PHOT’s Photonics Innovation Center.
We present an example of design, tolerancing and fabrication of freeform plastic lightguides for optical sensing applications. The design of the lightguides relies on Nonimaging Optics principles and uses raytracing simulations for analysis and optimization. We examine the influence of fabrication parameters on the simulated performance and show ways to minimize their impact. The presented lightguides have been fabricated at the Photonics Innovation Center of VUB – B-PHOT.
Optical fiber-sensors based on biodegradable and biocompatible optical fibers can be considered for implantation and invivo biosensing applications. We report on the fabrication and characterization of microstructured biodegradable and biocompatible polymer optical fibers (mbioPOF) from poly(D,L-lactic acid) (PDLLA), which is a commercially available polyester regulated by the U.S. FDA. We manufactured the optical fiber preforms by means of a novel technique based on transfer molding and subsequently we fabricated microstructured optical fibers using a standard heat-draw tower. The attenuation coefficient of our mbioPOF is as low as 0.065 dB∕cm at 898 nm for a microstructured fiber with a diameter of 219±27 μm. Prolonged immersion of mbioPOFs in PBS at 37°C leads to an increase of the optical loss with only 0.4 dB/cm after 6h and with 0.8 dB/cm after 17h, as measured at a wavelength of 950 nm.
We present a miniature freeform lightguide for sensing applications, designed according to the principles of the flow-line method from Nonimaging Optics. The optic is obtained by combining two 2D flow-line concentrators in a curved monolithic piece, achieving 45° half-acceptance angle and 40° beam steering in a very compact volume (about 1.3 x 2.0 x 20 mm3). We show how the initial design has been adjusted after a thorough tolerance analysis and describe its fabrication through plastic injection molding. The design of the mold involves a non-standard 3D-puzzle approach, which allows uniform high optical quality and minimizes the fillet radius on the optic.
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