Michael Vervaeke

Vrije Universiteit Brussel | VUB · Applied Physics and Photonics (TONA)

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 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...

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...

jats:p>Emerging applications requiring light beam manipulation, such as high-efficiency sunlight concentrators for solar cells, switchable micro-lens arrays for autostereoscopic displays, tunable lenses for augmented reality goggles, auto-focusing spectacles, and smart contact lenses, mostly depend on one or more active optical components with the...

We present an optical signal coupling scheme for slab waveguide surface grating coupler sensors. The proposed solution is based on the use of polymer microlenses. In this work we analyze two types of compact polymer lenses: the aspheric plano-convex lenses and Fresnel lenses. The feasibility of the proposed scheme is demonstrated by the experimenta...

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.

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 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 report on efficient optical beam-steering using a hot-embossed reflective blazed grating in combination with liquid crystal. A numerical simulation of the electrical switching characteristics of the liquid crystal is performed and the results are used in an FDTD optical simulator to analyze the beam deflection. The corresponding experiment on th...

Laser beam shaping at focus or focal beam shaping is essential for many applications. The most common approach makes use of the Fourier transforming properties of lenses to generate at their focal planes the desired irradiance patterns, e.g., the flattop. There are two inherent limitations for this approach. First, the shaping quality depends stron...

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 this work, we report two types of electrically tunable photonic devices with circularly symmetric polarization independent beam steering performance (beam condensing resp. beam broadening). The devices consist of circular micro grating structures combined with nematic liquid crystal (LC) layers with anti-parallel alignment. A single beam deflect...

Focal beam shaping (FBS), or laser beam shaping at focus, is required in many laser applications. The most common approach is to use a phase element and a Fourier transform lens to generate at the focal plane of the lens the desired irradiance pattern, usually a at-top. The shaping quality depends strongly on a dimensionless parameter β. In case of...

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 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 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...

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 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...

In this article, we describe an electrically switchable light beam steering component, based on the combination of microprism structures and nematic liquid crystals, which effectively deflects both a laser beam and a collimated white light beam with a controllable steering range of 38.

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...

Changeable laser image is a security feature commonly used on personalized documents. To understand and to predict the influence of different design parameters, a holistic optical modeling approach is essential. In this work a two-stage modeling process is performed using geometric ray tracing methods. The first stage, based on a basic optical mode...

We present an optofluidic lab-on-chip for confocal Raman spectroscopy, which can be used for the analysis of substances. The device strongly suppresses unwanted background signals because it enables confocal detection of Raman scattering thanks to a free-form reflector embedded in the optofluidic chip. We design the system using non-sequential ray-...

In this work we report the fabrication of polymer micro-photonic gratings for use in liquid-crystal based actively tunable electro-optic components. The gratings are produced by moving the sample surface sideways across a perpendicularly impinging KrF excimer laser beam (λ = 248 nm), which is shaped by specially designed triangular and trapezoidal...

In this work, the reverse replication of circular micro grating structures on glass substrates is implemented using an ultra-violet curable resin and a polydimethylsiloxane (PDMS) mold which has the same structure as the original circular grating master. Two different techniques (“double PDMS replication” and “polymer- PDMS replication”) are employ...

In this paper, we present an electrically controllable microoptical component for light beam steering and light intensity distribution built on the combination of nematic liquid crystal (LC) and polymer microprisms. Polymer microprism arrays are fabricated using soft embossing with elastic polydimethylsiloxane molds and ultraviolet curable resins....

We present numerical simulations of a monitoring technique for passive optical networks. The proposed technique is based on using an optical time domain reflectometer with fiber Bragg gratings which collaborate with the information provided by the Rayleigh backscattered power to distinguish between the different branches in the network. This will a...

Refocusing multi-channel imaging systems are nowadays commercially available only in bulky and expensive designs. Compact wafer-level multi-channel imaging systems have until now only been published without refocusing mechanisms, since classical refocusing concepts could not be integrated in a miniaturized configuration. This lack of refocusing cap...

A refractive laser beam shaper typically consists of either two plano-aspheric lenses or one thick lens with two aspherical surfaces. Ray mapping is a general optical design technique for irradiance reshaping based on geometric optics. Although ray mapping, in principle, allows generating any rotational-symmetric irradiance profile, in the literatu...

We present a miniaturized polymer-based micro-optical detection unit for ultraviolet and visible laser-induced fluorescence (LIF) and absorbance (ABS) analysis with an interaction length of 3 mm. We use non-sequential optical ray tracing simulations to model the system and to optimize its performance with respect to optical efficiency and system co...

In this article we report the fabrication of large arrays of micro-optical gratings using soft embossing with elastic Polydimethylsiloxane (PDMS) molds and ultra-violet (UV) curable resins. Three different kinds of resins are used to replicate the master gratings in a process akin to a roll to roll process. The optical surface profiling measurement...

Multichannel imaging systems currently feature refocusing capabilities only in bulky and expensive designs. Mechanical movements of the components cannot be integrated in miniaturized designs, preventing classical refocusing mechanisms. To overcome this limitation we developed, as a proof-of-concept (POC) demonstration, a compact low-cost two-chann...

Organic light-emitting diodes (OLEDs) are most frequently used for display purposes and while they have also been utilized in sensing applications, their innate compliance has not previously been exploited for these applications. However, in this manuscript it is shown that OLEDs are compatible with microfabrication methods used in the production o...

In this paper we demonstrate the proof-of-concept of an optofluidic module capable of simultaneous laser-induced fluorescence (LIF) and absorbance (ABS) detection based on total internal reflection (TIR) optics. We discuss the design of the optofluidic detection module, its fabrication, and the setup used for the proof-of-concept. The injection of...

There is a steady increase in the demand for internet bandwidth, primarily driven by cloud services and high-definition video streaming. Europe's Digital Agenda states the ambitious objective that by 2020 all Europeans should have access to internet at speeds of 30Mb/s or above, with 50% or more of households subscribing to connections of 100Mb/s....

A Gaussian laser beam is reshaped to have specific irradiance distributions in many applications in order to ensure optimal system performance. Refractive optics are commonly used for laser beam shaping. A refractive laser beam shaper is typically formed by either two plano-aspheric lenses or by one thick lens with two aspherical surfaces. Ray mapp...

Organic light-emitting diodes (OLEDs) are used almost exclusively for display purposes. Even when implemented as a sensing component, it is rarely in a manner that exploits the possible compliance of the OLED. Here it is shown that OLEDs can be integrated into compliant mechanical micro-devices making a new range of applications possible. A light-m...

We present an advanced simulation tool for optical time-domain reflectometry (OTDR) with the ability to incorporate any OTDR pulse shape. According to our knowledge, the proposed OTDR simulator is the first one with this feature, thus progressing beyond the existing state of the art of OTDR simulations. Starting from a mathematical formalism, we de...

Multichannel imaging systems have several potential applications such as multimedia, surveillance, medical imaging and machine vision, and have therefore been a hot research topic in recent years. Such imaging systems, inspired by natural compound eyes, have many channels, each covering only a portion of the total field-of-view of the system. As a...

In conventional multichannel imaging systems, all channels have similar imaging properties [field-of-view (FOV) and angular resolution]. In our approach, channels are designed to have different imaging properties which add multiresolution capability to the system. We have experimentally demonstrated, for the first time to our knowledge, a three-cha...

The use of photonics in data communication and numerous other industrial applications brought plenty of prospects for innovation and opened up different unexplored market opportunities. This is a major driving force for the fabrication of micro-optical and micro-mechanical structures and their accurate alignment and integration into opto-mechanical...

We developed integrated plastic micro-optical detection units for absorbance and fluorescence measurements in various types of microfluidic channels. For each system we present the complete development process from optical design, to fabrication and proof-of-concept demonstration.

We present micro-optical detection units for both laser-induced fluorescence and absorbance analysis. The detection systems are designed by means of non-sequential ray tracing simulations and prototyped by means of deep proton writing. In a proof-of-concept demonstration, the micro-optical unit is used for the detection of various concentrations of...

Fiber-To-The-Home (FTTH) networks have been adopted as a potential replacement of traditional electrical connections for the 'last mile' transmission of information at bandwidths over 1Gb/s. However, the success and adoption of optical access networks critically depend on the quality and reliability of connections between optical fibers. In particu...

One of the important challenges for the deployment of the emerging breed of nanotechnology components is interfacing them with the external world, preferably accomplished with low-cost micro-optical devices. For the fabrication of this kind of micro-optical components, we make use of deep proton writing (DPW) as a generic rapid prototyping technolo...

We present the results of a study to assess the viability of optical datacommunication solutions to alleviate the demands regarding power consumption and aggregate bandwidth imposed on future satellite communication payloads. Optimiza- tion of the satellite real-estate usage push payload designers towards very large capacity, high computational and...

Proceedings of the SPIE - The International Society for Optical Engineering Vol.7716, 77161E The increased demand of broadband communication services like High Definition Television, Video On Demand, Triple Play, fuels the technologies to enhance the bandwidth of individual users towards service providers and hence the increase of aggregate bandwid...

The advent of Plastic Optical Fibre (POF) opened perspectives for numerous applications in the field of datacommunications. POF is increasingly popular in the automotive industry as a robust, lightweight, electromagnetic interference free, easy and cheap to install alternative to electrical wiring for high-speed entertainment, navigation and data a...

One of the most important challenges in multiple-fiber connectors is to achieve accurate fiber positioning, i.e. to ensure that the fiber end facets coincide with the front facet of the connector plate. Therefore, it is crucial to increase the accuracy of the assembly process of fiber connectors. We present the population of a plastic multi-fiber c...

One of the important challenges for the deployment of the emerging breed of nanotechnology components is interfacing them with the external world, preferably accomplished with low-cost micro-optical devices. For the fabrication of this kind of micro-optical modules, we make use of deep proton writing (DPW) as a generic rapid prototyping technology....

We present an interferometric setup for in situ monitoring of fiber tip positions when inserting optical fibers for fixation in fiber connector components. It ensures an accurate fiber tip position at the fiber connector's front facet and across the fiber array in cases where postinsertion polishing is not possible. We demonstrate our technique by...

We report on different optical coupling concepts between resonant-cavity light-emitting diodes and plastic optical fiber for the automotive according to the multimedia oriented systems transport standard. We present five different candidate optical coupling schemes. Two coupling schemes were investigated in depth regarding manufacturing and assembl...

We present a peripheral fiber connector to seamlessly interface optical fiber ribbons with polymer optical waveguides integrated on a Printed Circuit Board (PCB). Laser ablation was used to fabricate the optical board, featuring alignment features which enable an accurate positioning of an alignment plate carrying MT-compatible guide pins. These al...

Today a lot of applications (datacommunication, automation, sensing, automotive . . . ) make use of plastic optical fibers (POF) to carry data over short distances. In this paper we will focus on the case study of a resonant cavity light emitting diode (RCLED) in combination with a POF. First we compare the optimal coupling efficiency of different...

In this work we present a tolerance aware design flow for passive micro-optical modules. Concretely, we apply the process to a free-space intra-chip interconnection module which has been prototyped with the deep proton writing technology.

One of the grand challenges in solving the interconnection bottlenecks at the printed circuit board (PCB) and multi-chip-module (MCM) level, is to adequately replace the PCB and intra-MCM galvanic interconnects with high-performance, low-cost, compact and reliable micro-photonic alternatives. Therefore we address the following components in this pa...

One of the grand challenges in solving the interconnection bottlenecks at the Printed Circuit Board (PCB) and Multi-Chip-Module (MCM) level, is to adequately replace the PCB and intra-MCM galvanic interconnects with high-performance, low-cost, compact and reliable micro-photonic alternatives. Therefore we address the following components in this pa...

This study aims at proving that single photon sensing can be made accessible in the form of cheap off-the-shelf micro-devices with micro-optical/micromechanical coupling systems. In order to achieve this challenging goal, use is made of different micro-technologies, not yet fully established but promising and innovative in and of themselves. It is...

We report on the opto-mechanical design and performances of an intra-multi-chip-module free-space optical interconnect, integrating microlenses and a deflection prism above a dense opto-electronic chip, under various fabrication and assembly errors. To this aim we have built an opto-mechanical model of the complete interconnect. The model allows us...

One of the important challenges to deploying the emerging breed of nanotechnology components is interfacing them with the external world, preferably accomplished with low-cost micro-optical devices. In our labs at the Vrije Universiteit Brussel (VUB), we are therefore focusing on the continuous development of a rapid prototyping technology for the...