Jan-Willem Hoste

Improving the detection limit of conformational analysis by utilizing a dual polarization Vernier cascade.

The dual polarization microring technique enables the simultaneous and accurate detection of thickness and refractive index of a bound molecular layer. By using three microring resonators in a double Vernier cascade configuration, the dual polarization technique is improved on three distinct levels: an increase of the sensitivity, a suppression of common noise due to self-referencing and the ability to migrate from a standard tunable laser to a cheap broadband LED and an on-chip arrayed waveguide grating as read-out system, allowing for a system which is orders of magnitude faster and cheaper. A dual polarization Vernier cascade proof-of-concept is fabricated and characterized, a read-out computational framework is constructed and it is shown on a theoretical basis that the limit of detection is improved.

Silicon photonics biosensing: different packaging platforms and applications

We present two different platforms integrating silicon photonic biosensors. One is based on integration with reaction tubes to be compatible with traditional lab approaches. The other uses through-chip fluidics in order to achieve better mixing of the analyte.

Ring resonator based SOI biosensors

In this paper, two recent advances in silicon ring resonator biosensors are presented. First, we address the problem that due to the high index contrast, small deviations from perfect symmetry lift the degeneracy of the normal resonator mode. This severely deteriorates the quality of the output signal. To address this, we discuss an integrated interferometric approach to give access to the unsplit, high-quality normal modes of the microring resonator. Second, we demonstrate how digital microfluidics can be used for effective fluid delivery to nanophotonic microring resonator sensors fully constructed in SOI.

Silicon Ring Resonator-Based Biochips

This chapter discusses the use of silicon photonics biochips incorporating ring resonator sensors. After an introduction to the ring sensor, we will discuss other aspects like peak splitting compensation, the exploitation of the Vernier effect for increased sensitivity, and the use of dual-polarization rings to determine conformational information.

Highly sensitive detection using microring resonator and nanopores

One of the most significant challenges facing physical and biological scientists is the accurate detection and identification of single molecules in free-solution environments. The ability to perform such sensitive and selective measurements opens new avenues for a large number of applications in biological, medical and chemical analysis, where small sample volumes and low analyte concentrations are the norm. Access to information at the single or few molecules scale is rendered possible by a fine combination of recent advances in technologies. We propose a novel detection method that combines highly sensitive label-free resonant sensing obtained with high-Q microcavities and position control in nanoscale pores (nanopores). In addition to be label-free and highly sensitive, our technique is immobilization free and does not rely on surface biochemistry to bind probes on a chip. This is a significant advantage, both in term of biology uncertainties and fewer biological preparation steps. Through combination of high-Q photonic structures with translocation through nanopore at the end of a pipette, or through a solid-state membrane, we believe significant advances can be achieved in the field of biosensing. Silicon microrings are highly advantageous in term of sensitivity, multiplexing, and microfabrication and are chosen for this study. In term of nanopores, we both consider nanopore at the end of a nanopipette, with the pore being approach from the pipette with nanoprecise mechanical control. Alternatively, solid state nanopores can be fabricated through a membrane, supporting the ring. Both configuration are discussed in this paper, in term of implementation and sensitivity.

Determination of thickness and density of a wet multilayer polymer system with sub-nanometer resolution by means of a dual polarization silicon-on-insulator microring

Determination of both thickness and refractive index of a thin biomolecular or polymer layer in wet conditions is a task not easily performed. Available tools such as XPS, AFM, ellipsometry and integrated photonic sensors often have difficulties with the native wet condition of said agents-under-test, perform poorly in the sub-5 nm regime or do not determine both characteristics in an absolute simultaneous way. The thickness of a multilayer system is often determined by averaging over a large amount of layers, obscuring details of the individual layers. Even more, the interesting behavior of the first bound layers can be covered in noise or assumptions might be made on either thickness or refractive index in order to determine the other. To demonstrate a solution to these problems, a silicon-on-insulator (SOI) microring is used to study the adsorption of a bilayer polymer system on the silicon surface of the ring. To achieve this, the microring is simultaneously excited with TE and TM polarized light and by tracking the shifts of both resonant wavelengths, the refractive index and the thickness of the adsorbed layer can be determined with a resolution on thickness smaller than 0.1 nm and a resolution on refractive index smaller than 0.01 RIU. An adhesive polyethyleneimine (PEI) layer is adsorbed to the surface, followed by the adsorption of poly(sodium-4-styrene sulfonate) (PSS) and poly(allylamine) hydrochloride (PAH). This high-resolution performance in wet conditions with the added benefits of the SOI microring platform such as low cost and multiplexibility make for a powerful tool to analyze thin layer systems, which is promising to research binding conformation of proteins as well.

Employing a dual polarisation microring to determine refractive index and thickness of a thin polymer layer

Dual polarisation biosensing is a novel optical technique that focuses on retrieving structural information from a bound or adsorbed layer of molecules, by using a silicon-on-insulator (SOI) microring. Both density and thickness of the layer can be monitored simultaneously. Due to a self-calibrating protocol that is quickly performed at the start of every experiment, a high accuracy can be obtained. In this paper, we determine the thickness and refractive index of a thin layer of polyethyleneimine (PEI), which adsorbs to the silicon surface of the microring. This results in a layer with a thickness of 1.158 and a refractive index of 1.453 RIU.