Jurgen Van Erps

• PhD in Engineering, Master in Photonics Engineering
• Professor at Vrije Universiteit Brussel

Besides major advantages for telecommunication applications, vertical-cavity surface-emitting lasers (VCSELs) have attracted interest for their potential for neuro-inspired computing, frequency comb generation, or high-frequency spin oscillations. In the meantime, strain applied to the laser structure has been shown to have a significant impact on...

The deployment and advancement of high‐bandwidth communication networks, quantum information systems, and sensing platforms relying on multi‐core optical fibers (MCFs) are challenged by the scarcity of cost‐effective, compact, and efficient optical interfacing components. This study introduces an unprecedented 3D‐printed 1 × 4 splitter for MCFs fab...

Besides major advantages for telecommunication applications, VCSELs have attracted interest for their potential for neuro-inspired computing, frequency comb generation or high-frequency spin oscillations. In the meantime, strain applied to the laser structure has been shown to have a significant impact on the laser emission properties such as the p...

We present a procedure for the design of multilevel metalenses and their fabrication with multiphoton-based direct laser writing. This work pushes this fast and versatile fabrication technique to its limits in terms of achievable feature size dimensions for the creation of compact high-numerical aperture metalenses on flat substrates and optical fi...

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 presents the design, fabrication, and characterization of such dosimeters, consisting of scintillating sensor tips attached to polymer opti...

We used triangular cross-section multimode interference coupler, S-bends, and adiabatic tapers as building blocks to design and fabricate ultracompact 3D splitters for multi-core optical fiber with an insertion loss below -3 dB per channel.

Artificial photosynthesis has rapidly developed as an actual field of research, mimicking natural photosynthesis processes in plants or bacteria to produce energy or high-value chemicals. The nanocelluloses are a family of biorenewable materials that can be engineered into nanostructures with favorable properties to serve as a host matrix for encap...

The third-generation of gravitational wave observatories, such as the Einstein Telescope (ET) and Cosmic Explorer (CE), aim for an improvement in sensitivity of at least a factor of ten over a wide frequency range compared to the current advanced detectors. In order to inform the design of the third-generation detectors and to develop and qualify t...

The speed of production in laser-based additive manufacturing processes is rather low compared to conventional manufacturing methods and could be improved by using a top-hat laser beam intensity profile, a variable spot size or a combination of both, enabling wider melt pools during processing. This while retaining or possibly even improving part q...

This paper reports the characterization of two scintillating materials in powder form, Gadox and YVO embedded in a light-activated resin, used in a probe developed for oncological brachytherapy in-vivo dosimetry. The materials were characterized in terms of internal absorption, scintillation decay time, and light yield. The measurement of the optic...

Multichannel imaging systems consist of multiple channels that have different imaging characteristics (fields-of-view and angular resolutions). We design and demonstrate a six-channel multiresolution imaging system that can achieve a relative magnification ratio of up to 10 times between the channels and, at the same time, result in different depth...

We designed, fabricated and characterized low loss and polarization independent waveguide Bezier-shape S-bends. We optimized the shape parameter to obtain the shortest length for a given S-bend offset.

The continuous quest for chromatographic supports offering kinetic performance properties superior to that of the packed bed of spheres has pushed the field to consider alternative formats such as for example monolithic and pillar array columns. This quest seems bound to culminate in the use of 3D printing technology, as this intrinsically offers t...

We present the development of a compact (about 1.3 × 2.0 × 20 mm³) freeform optical lightguide for sensing applications, from the conceptual design to the fabrication through injection molding. The design of the optic is based on the flow-line method from Nonimaging Optics, which allows the desired optical functionalities (45° half-acceptance and 4...

Despite the rapid developments in the field of two-photon polymerization-based direct laser writing, limited attention has been paid to the efficient design of optical waveguide-based building blocks. To fill that gap, we have numerically investigated air-clad waveguides, tapers, and S-bends, with the aim to minimize insertion losses, whilst reduci...

We present our latest results on the design and fabrication of mode-field conversion tapers for low-loss optical interconnects. These structures are fabricated by means of two-photon polymerization-based 3D nanoprinting. We experimentally demonstrate that our 3D nanoprinted downtapers outperform conventional lensed fibers for low-loss edge coupling...

We present the fabrication of a micromirror array through ultraprecision diamond milling to be used as a master in a nanoimprint replication process. The master also includes alignment features to allow step-and-repeat tiling during the replication.

We present the design, fabrication and characterization of mode conversion down- tapers printed directly on single-mode fiber tips, enabling high-efficiency physical contact edge- coupling connections to various photonic integrated chips.

We present a freeform lightguide comprising two 2D flow-line concentrators to achieve 45° acceptance angle in 3D, under particularly strict mechanical constraints. The design has been optimized for injection molding fabrication.

Photocrosslinkable gelatin hydrogels are excellent bioinks or biomaterial ink components to serve biofabrication applications. Especially the widely investigated gelatin-methacroyl hydrogels hold an impressive track record. However, over the past decade, increasing attention is being paid to thiol-ene photo-click chemistry to obtain hydrogel networ...

We present a design and fabrication approach for 3D printed polymer microstructured optical fiber tapers on standard single-mode glass fibers for efficient and compact mode-field conversion. This paves the way towards complex functionalized fiber tips for various applications, like sensors and beam shaping components, currently limited by the mode-...

Compact and broadband spectrometers are very useful in various application domains such as agriculture, food, health and security. In minimally-invasive image-guided procedures spectral tissue sensing helps for screening and diagnostic purposes aiming at discriminating between healthy and tumorous tissue at point-of-care locations and outpatient ce...

No general approach is available yet to measure directly the ratio between chromatic dispersion and the nonlinear coefficient, and hence the soliton number for a given optical pulse, in an arbitrary guiding medium. Here we solve this problem using continuum generation. We experimentally demonstrate our method in polarization-maintaining and single-...

Corneal blindness is the fourth leading cause of visual impairment. Of specific interest is blindness due to a dysfunctional corneal endothelium which can only be treated by transplanting healthy tissue from a deceased donor. Unfortunately, corneal supply does not meet the demand with only one donor for every 70 patients. Therefore, there is a huge...

Connections between standard single-mode fibers and waveguides in photonic integrated circuits tend to have relatively high coupling losses due to a difference in mode size and mode profile between both light guiding media. Edge coupling strategies involving specialty fibers are frequently used to obtain the best performance in terms of coupling ef...

Improved chemical- and bio-sensing with Surface Enhanced Raman Spectroscopy (SERS) requires nanostuctures that can be flexibly designed and fabricated with different physical and optical properties. Here, we present nano-pillar arrays ranging from 200 nm to 600 nm as SERS substrates for mycotoxin detection that are fabricated by means of two-photon...

Stem cells are characterized by their self-renewal capacity and their ability to differentiate into multiple cell types of the human body. Using directed differentiation strategies, stem cells can now be converted into hepatocyte-like cells (HLCs) and therefore, represent a unique cell source for toxicological applications in vitro. However, the ac...

Over the recent decades gelatin has proven to be very suitable as an extracellular matrix mimic for biofabrication and tissue engineering applications. However, gelatin is prone to dissolution at typical cell culture conditions and is therefore often chemically modified to introduce (photo-)crosslinkable functionalities. These modifications allow t...

We present the design of refractive beam shaping optics for transforming a circular Gaussian beam into a top hat beam for an additive manufacturing process. The designed components are prototyped in zinc sulfide using single-point diamond turning.

Surface Plasmon Resonance devices have the promise to become the prevailing device technology for miniaturized point-of-care diagnosis. We have designed, fabricated and tested a disposable freeform SPR device outperforming traditional prism devices.

The physics of nonlinear-optical refraction in graphene has remained unclear for almost a decade now. We solve this issue through self-phase modulation experiments in graphene-covered waveguides, revealing the extra-ordinary free-carrier interactions that underpin the refraction process.

Over the recent decades gelatin has proven to be very suitable as an extracellular matrix mimic for bio-fabrication and tissue engineering applications. However, gelatin is prone to dissolution at typical cell culture conditions and is therefore often chemically modified to introduce (photo-)crosslinkable functionalities. These modifications allow...

We report on the design, fabrication and experimental demonstration of single-crystal diamond (SCD) waveguide devices with integrated grating couplers optimized for 850 nm, 635 nm, and 405 nm wavelengths, respectively. The devices are fabricated on SCD thin films using electron-beam lithography and reactive-ion etching technologies. To reduce the w...

Small misalignments between two standard telecom single-mode fibers in a physical contact connection can lead to large optical losses. It is known that by expanding the mode field diameter of the fiber, the misalignment tolerances can be relaxed. One of the approaches to obtain this beam expansion is to use tapers. We propose an air-clad taper stru...

Applying graphene in optical and photonic applications is anticipated to be a promising strategy to attain new technological functionalities. To maximize the exploitation of graphene’s extraordinary optical properties, precise control over its Fermi level will be of vital importance. Therefore, chemical doping is a viable approach to manipulate gra...

Graphene is considered a record-performance nonlinear-optical material on the basis of numerous experiments. The observed strong nonlinear response ascribed to the refractive part of graphene's electronic third-order susceptibility χ(3) cannot, however, be explained using the relatively modest χ(3) value theoretically predicted for the 2D material....

In the present work, gelatin type B is modified with highly reactive norbornene functionalities (Gel‐NB) following a one‐pot synthesis approach to enable subsequent thiol–ene photo‐click crosslinking. The modification strategy displays close control over the amount of introduced functionalities. Additionally, Gel‐NB exhibits considerably improved p...

Single-crystal diamond (SCD) is a promising material for integrated photonics, yet technologically challenging. We show how to overcome these challenges and demonstrate long waveguides, efficient gratings and wideband directional couplers in SCD.

We solve the long-standing discrepancy between the theoretically predicted and experimentally observed performance of nonlinear-optical refraction in graphene. Hereto we study self-phase modulation in silica-core waveguides covered with graphene.

The present work reports on the development of photo-crosslinkable gelatins sufficiently versatile to overcome current biopolymer two-photon polymerization (2PP) processing limitations. To this end, both the primary amines as well as the carboxylic acids of gelatin type B were functionalized with photo-crosslinkable moieties (up to 1 mmol/g) result...

We present our technology supply chain for freeform polymer optics. We show through recent examples how this technology supply chain is a key-enabler for frontier applied research and demonstrate how it paves the way towards efficient technology take-up and effective industrial innovation.

Deep proton writing (DPW) is a fabrication technology developed for the rapid prototyping of polymer micro-structures. We use SU-8, a negative resist, spincoated in a layer up to 720 μm-thick in a single step on borosilicate glass, for irradiation with a collimated 12 MeV energy proton beam. Micro-pillars with a slightly conical profile are irradia...

Deep proton writing (DPW) is a fabrication technology developed for the rapid prototyping of polymer microstructures. We use polymethylmethacrylate (PMMA) substrates, which act as a positive resist, for irradiation with a collimated 12-MeV energy proton beam. Using 12 MeV enables the irradiation of increasingly thick PMMA substrates with less conic...

We experimentally demonstrate a negative Kerr nonlinearity for quasiundoped graphene. Hereto, we introduce the method of chirped-pulse-pumped self-phase modulation and apply it to graphene-covered silicon waveguides at telecom wavelengths. The extracted Kerr-nonlinear index for graphene equals n2,gr=−10^(−13) m^2/W. Whereas the sign of n2,gr turns...

This paper presents the hot-embossing replication of self-centering fiber alignment structures for high-precision, single-mode optical fiber connectors. To this end, a metal mold insert was fabricated by electroforming a polymer prototype patterned by means of deep proton writing (DPW). To achieve through-hole structures, we developed a postembossi...

Raman spectroscopy is a powerful optical and non-destructive technique and a well-known method for analysis purposes, especially to determine the molecular fingerprint of substances. Traditionally, such analyses are done in a specialized lab, with considerable requirements in terms of equipment, time and manual sampling of substances of interest. I...

In recent years the integration of graphene into silicon photonics has attracted much attention as it allows using well-established CMOS technology for constructing next-generation photonic integrated circuits. Because of graphene's extraordinary optical properties, the deposition of graphene on top of silicon photonic chips can further enhance the...

The European Commission’s goal of providing each European household with at least a 30 Mb s⁻¹ Internet connection by 2020 would be facilitated by a widespread deployment of fibre-to-the-home, which would in turn be sped up by the development of connector essential components, such as high-precision alignment features. Currently, the performance of...

We present the use of femtosecond laser ablation for the removal of monolayer graphene from silicon-on-insulator (SOI) waveguides, and the use of oxygen plasma etching through a metal mask to peel off graphene from the grating couplers attached to the waveguides. Through Raman spectroscopy and atomic force microscopy, we show that the removal of gr...

We present a microfluidic chip in Polymethyl methacrylate (PMMA) for optical trapping of particles in an 80μm wide microchannel using two counterpropagating single-mode beams. The trapping fibers are separated from the sample fluid by 70μm thick polymer walls. We calculate the optical forces that act on particles flowing in the microchannel using w...

With the demand for broadband connectivity on the rise due to various services like video-on-demand and cloud computing becoming more popular, the need for better connectivity infrastructure is high. The only future- proof option to supply this infrastructure is to deploy "fiber to the home" (FTTH) networks. One of the main difficulties with the de...

It is known that cleaving an optical fiber introduces a number of irregularities and defects to the fiber’s end-face, such as hackles and shockwaves. These defects can act as failure initiators when stress is applied to the end-face. Given the fiber’s small diameter of 125 ffm, a large amount of mechanical stress can be expected to be applied on it...

Over the past decades, solid freeform fabrication (SFF) has emerged as the main technology for the production of scaffolds for tissue engineering applications as a result of the architectural versatility. However, certain limitations have also arisen, primarily associated with the available, rather limited range of materials suitable for processing...

We present an optofluidic chip in polymethyl methacrylate (PMMA) that combines optical trapping of single particles with confocal Raman spectroscopy. We introduce the design of the optofluidic chip and the ray-tracing simulations combined with mathematical calculations used to determine the optical forces exerted on the particles and to model the e...

In parallel with the development of nanoparticle coatings for protection of paper substrates, detailed descriptions of the surface topography with micro- to nanoscale roughness features are needed. In this work, papers have been coated with poly(styrene-co-maleic anhydride) nanoparticles including different types of vegetable oils and the surface r...

We show a detection system that simultaneously allows absorbance (ABS), laser-induced fluorescence (LIF) and scattering detection excited by two different laser sources at 405 nm and 450 nm. The heart of the system consists of a mass manufacturable polymer optofluidic chip. The chip is mounted in an optical detection assembly that aligns the chip t...

We present a microfluidic chip in Polymethyl methacrylate (PMMA) for optical trapping of particles in an 80µm wide microchannel using two counterpropagating single-mode beams. The trapping fibers are separated from the sample fluid by 70µm thick polymer walls. We calculate the optical forces that act on particles flowing in the microchannel using w...

We present a new approach to remove monolayer graphene transferred on top of a silicon-on-insulator (SOI) photonic integrated chip. Femtosecond laser ablation is used for the first time to remove graphene from SOI waveguides, whereas oxygen plasma etching through a metal mask is employed to peel off graphene from the grating couplers attached to th...

We present our polymer micro-optics technology supply chain and its key constituents. We show how it is a key-enabler for frontier applied research and demonstrate how it paves the way towards efficient technology take-up and effective industrial innovation.

The present work describes for the first time the production of self-supporting low gelatin density (<10 w/v%) porous scaffolds using methacrylamide-modified gelatin as an extracellular matrix mimicking component. As porous scaffolds starting from low gelatin concentrations cannot be realized with the conventional additive manufacturing techniques...

We show a proof-of-concept demonstration of a multi-parameter analysis low-cost optical detection system for the flowcytometric identification of vinegars. This multi-parameter analysis system can simultaneously measure laser induced fluorescence, absorption and scattering excited by two time-multiplexed lasers of different wavelengths. To our know...

Conventional multichannel imaging systems comprise of many optical channels having similar imaging properties, namely field-of-view (FOV) and angular resolution/magnification. We demonstrated that the different optical channels can be designed such that each optical channel captures a different FOV and angular resolution compared to its neighboring...