Method of manufacturing a micro unit and a micro unit for use in a microscope

The invention relates to a method of manufacturing a micro unit for use in a microscope. The method comprises the step of providing a planar substrate supporting structure and creating a chamber in the supporting structure for receiving a fluid containing a chemically reacting substance to be inspected. Further, the method comprises the step of coating an inner surface of the chamber with a thin layer. The method also comprises the step of locally removing material from the exterior of the supporting structure until the thin layer is reached for forming a window segment that is at least partially transparent to a beam of radiation generated by the microscope.MicroelectronicsElectrical Engineering, Mathematics and Computer Scienc

Dispersion resulting from wide passband shape in 50-GHz-spaced wavelength router

Electronic Instrumentation LaboratoryElectrical Engineering, Mathematics and Computer Scienc

Simple optical characterisation for biomimetic micromachined silicon strain-sensing structure

This paper presents an on-going work to develop micromachined silicon-based strain sensor inspired from the campaniform sensillum of insects. We present simple optical setup for the characterisation of a membrane-in-recess structure as an early stage in mimicking the natural sensor. The microstructure is a 500 nm-thick SiO2/SiN circular membrane, burried 13 ?m from the surface of a 3x3 mm, 525 ?m thick Si-chip. The chip was attached to a 45x10x0.525 mm Si beam. The simple optical characterisation setup is based on imaging the reflected laser beam from the biomimetic structure. Since an optical cavity between the membrane and the Si beams beneath was formed, ideal flat-parallel Fabry-Perot interferometer equation was applied to interpret the results semi-quantitatively. We obtained 2-D interference fringe pattern having 3 orders of maxima from the middle to the edge of the circular apperture, as a result of an initial internal membrane stress. The pattern changed non-linearly as we applied flexural strain from behind the beam up to 50 ?m, most probably caused by nonlinear deflection of the membrane (i.e. the membrane did not deflect similarly as the beam beneath it). This phenomena might explain one of the strain-amplifying properties of this biomimetic strain sensing microstructure.Department of MicroelectronicsElectrical Engineering, Mathematics and Computer Scienc

Reflectance-based two-dimensional TiO2 photonic crystal liquid sensors

We propose and experimentally demonstrate a reflectance-based photonic crystal (PC) liquid sensor. The PC is made of two-dimensional TiO2 nanopillar arrays. Such a reflectance-based structure with large functional area not only simplifies the optical guiding but also enhances the sensor signal. A linear shift of reflectance peaks is found for liquids with refractive indices varying from 1.333 to 1.390 at wavelength near 1.5 ?m. Excellent agreement between measured values and the generated reflectance model at a fixed wavelength is obtained, indicating the high potential of these PC-based liquid sensors for biological and environmental applications.MicroelectronicsElectrical Engineering, Mathematics and Computer Scienc

Vertical SiC taper with a small angle fabricated by slope transfer method

In this Letter, a slope transfer method to fabricate vertical waveguide couplers is proposed. This method utilises wet etched Si as a mask, and takes advantage of dry etching selectivity between Si and SiC, to successfully transfer the profile from the Si master into SiC. By adopting this method, a <2° slope is achieved. Such a taper can bring the coupling efficiency in SiC waveguides to 80% (around 1 dB loss) or better from around 10% (10 dB loss) without taper. It further increases the alignment tolerance at the same time, which ensures the successful development of a plug-and-play solution for optical sensing. This is the first reported taper made in SiC.EKL ProcessingElectronic Instrumentatio

Sensing performance of plasma-enhanced chemical vapor deposition SiC-SiO2-SiC horizontal slot waveguides

We have studied, for the first time, the sensing capabilities of plasma-enhanced chemical vapor deposition (PECVD) SiC-SiO2-SiC horizontal slot waveguides. Optical propagation losses were measured to be 23.9 dB?cm for the quasi-transverse magnetic mode. To assess the potential of this device as a sensor, we simulated the confinement factor in the slot. This simulation revealed that SiC-based slot waveguides can be used, advantangeously, for sensing as the confinement strongly varies with the refractive index of the slot material. A confinement factor change of 0.15?refractive index units was measured for different slot materialsDelft Institute of Microsystems and NanoelectronicsElectrical Engineering, Mathematics and Computer Scienc

Characterization of low temperature deposited atomic layer deposition TiO2 for MEMS applications

TiO2 is an interesting and promising material for micro-/nanoelectromechanical systems (MEMS/NEMS). For high performance and reliable MEMS/NEMS, optimization of the optical characteristics, mechanical stress, and especially surface smoothness of TiO2 is required. To overcome the roughness issue of the TiO2 films due to crystallization during deposition at high temperatures (above 250?°C), low temperature (80–120?°C) atomic layer deposition (ALD) is investigated. By lowering the deposition temperature, the surface roughness significantly decreases from 3.64?nm for the 300?°C deposited crystalline (anatase phase) TiO2 to 0.24?nm for the 120?°C amorphous TiO2. However, the layers deposited at low temperature present different physical behaviors comparing to the high temperature ones. The refractive index drops from 2.499 to 2.304 (at 633?nm) and the stress sharply decreases from 684 to 133?MPa. Superhydrophilic surface is obtained for the high temperature deposited TiO2 under ultraviolet illumination, while little changes are found for the low temperature TiO2. The authors demonstrate that by suitable postdeposition annealing, all the properties of the low temperature deposited films recover to that of the 300?°C deposited TiO2, while the smooth surface profile (less than 1?nm roughness) is maintained. Finally, micromachining of the low temperature ALD TiO2 by dry etching is also studied.MicroelectronicsElectrical Engineering, Mathematics and Computer Scienc

Thermo-optical delay line for optical coherence tomography

Optical Coherence Tomography (OCT) is a powerful medical imaging technology. Its ability to non-invasively probe tissues in depth with high resolution has lead to applications in many fields of medicine, with a large potential for surgical guidance. One of the technological challenges impairing faster adoption of OCT is the relative complexity of the corresponding optical instrumentation, which translates into expensive and bulky setups. In this paper a compact fastscanning optical delay line based on the thermo-optical effect of silicon is studied. Although this effect has been applied to other optical components, the necessary frequency behaviour together with the relatively large scanning range required are unique to the application. Cycling speeds of over 1kHz and ranges of more than 1mm are needed for videorate acquisition of relevant tissue volumes. A structure is proposed to meet these specifications. A bulk micro machined freestanding waveguide is connected to the substrate by means of evenly spaced support beams. It is shown by means of the Finite Element Method that the geometrical parameters of the beams modulate the thermal behaviour of the waveguide. A linear trade-off between maximum working frequency and power dissipation for any given waveguide size and required scanning range has been found. Our results show that the proposed implementation of a fast-scanning delay line can match the requirements of Time Domain Optical Coherence Tomography.Electronic Instrumentation LaboratoryElectrical Engineering, Mathematics and Computer Scienc

Demonstration of PECVD SiC thermal delay lines for optical coherence tomography in the visible

Optical Coherence Tomography (OCT) has found applications in many fields of medicine and has a large potential for the optical biopsy of tumors. One of the technological challenges impairing faster adoption of OCT is the relative complexity of the optical instrumentation required, which translates into expensive and bulky setups. In this paper we report an implementation of Time-Domain Optical Coherence Tomography based on Plasma Enhanced Chemical Vapor Deposition (PECVD) Silicon Carbide (SiC). The devices, with a footprint of 0.3 cm2, are fabricated using rib waveguides defined in a SiC layer. While most of the components needed are known when using this material [1], a fast delay line with sufficient scanning range is a specific requirement of Time Domain (TD)-OCT. In the system reported here this is obtained making use of the thermo-optical effect. Though the current implementation still requires external sources and detectors to be coupled to the planar waveguide circuit, future work will include three-dimensional integration of these components onto the substrate to achieve a fully autonomous and compact OCT chip. With the potential to include the read-out and driving electronics on the same die, the reported approach can yield extremely compact and low-cost TD-OCT systems in the visible, enabling a broad range of new applications, including OCT devices for harsh environment.Laboratory of Electronic ComponentsElectrical Engineering, Mathematics and Computer Scienc

Biomimetic strain-sensing microstructure for improved strain sensor: Fabrication results and optical characterization

Electrical Engineering, Mathematics and Computer Scienc